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SID 5 Research Project Final Report
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NoteIn line with the Freedom of Information Act 2000, Defra aims to place the results of its completed research projects in the public domain wherever possible. The SID 5 (Research Project Final Report) is designed to capture the information on the results and outputs of Defra-funded research in a format that is easily publishable through the Defra website. A SID 5 must be completed for all projects.
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Project identification
1. Defra Project code HH3606
2. Project title
Sustainability of UK Strawberry Crop
3. Contractororganisation(s)
Agriculture & Environment Research Unit, Science and Technology Research InstituteUniversity of HertfordshireCollege LaneHatfieldHertsAL10 9AB
54. Total Defra project costs £ 150,157.00
5. Project: start date................ 01 July 2003
end date................. 30 June 2005
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6. It is Defra’s intention to publish this form. Please confirm your agreement to do so...................................................................................YES NO (a) When preparing SID 5s contractors should bear in mind that Defra intends that they be made public. They
should be written in a clear and concise manner and represent a full account of the research project which someone not closely associated with the project can follow.Defra recognises that in a small minority of cases there may be information, such as intellectual property or commercially confidential data, used in or generated by the research project, which should not be disclosed. In these cases, such information should be detailed in a separate annex (not to be published) so that the SID 5 can be placed in the public domain. Where it is impossible to complete the Final Report without including references to any sensitive or confidential data, the information should be included and section (b) completed. NB: only in exceptional circumstances will Defra expect contractors to give a "No" answer.In all cases, reasons for withholding information must be fully in line with exemptions under the Environmental Information Regulations or the Freedom of Information Act 2000.
(b) If you have answered NO, please explain why the Final report should not be released into public domain
Executive Summary7. The executive summary must not exceed 2 sides in total of A4 and should be understandable to the
intelligent non-scientist. It should cover the main objectives, methods and findings of the research, together with any other significant events and options for new work.
The desire for sustainability is well recognised within the UK agricultural industry although the means for its delivery are still largely unclear. Environmental impact assessments (EIA) are often used to aid the decision-making process in complex planning issues but may also be applied to agricultural systems through, for example, the use of models that assess pesticide risk to non-target species and through the formulation of energy and nutrient budgets.
A grower questionnaire, devised by East Malling Research, obtained detailed descriptions from 20 growers of the most typical methods of strawberry production in the UK. Differences included the use of soil fumigation, protection with polytunnels, organic production and whether soil or media grown. Typical outputs with respect to the quantity of saleable fruit per ha for each system were also provided. A total of 14 production systems were identified, with six additional sub-systems to give a total of 20 in all. All systems produced between one and two crops with the exception of Systems 1, 2 and 4 which produced up to three crops.
Three geographical locations were chosen from key strawberry growing areas with variation in weather patterns, soil type and groundwater vulnerabilities. They included the South-East (1006 ha) represented by Kent (59 % of production within the South East region), the East of England (602 ha) represented by Norfolk (55 % within the East of England region) and the West Midlands (512 ha) represented by Herefordshire (62 % within the West Midlands region). Production occurred on a range of soil types (sand, ‘other mineral’ and clay) and within different rainfall areas (low, moderate and high). Three descriptions of local wildlife habitats in and around strawberry enterprises in the three example locations were identified during visits to growers to incorporate sensitive habitat features such as surface water, woodland and species rich hedgerows
One of the largest environmental impacts from strawberry production is attributed to energy use. Previous energy balance studies have focused on arable crop production and found that the greatest contributor to energy input to be from the manufacture of mineral nitrogen fertiliser. For the UK strawberry crop that has a relatively low nitrogen requirement, the greatest energy inputs were associated with the manufacture of soil fumigants such as chloropicrin and with the plastic used for polytunnels and mulch. The overall energy input for strawberry production in the UK ranged between 15.8 to 168.3 GJ/ha. Energy efficiency per crop/ha for soil grown systems and container systems on raised beds may be improved with the growing of a second, or greater still, with a third crop assuming yields are maintained. The energy required for the manufacture of mulch and fumigants and the execution of field operations for bed preparation is shared between two or three crops as opposed to one. The recycling of plastics offers potential to reduce the energy input per crop significantly for most systems, particularly in protected crops. In general, for Junebearer crops, the improved yields associated with the protection of first year crops results in a similar or lower energy input per tonne of class 1 fruit than non-protected first year crops,
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particularly if the plastic is recycled. However, for those crops grown for a second year, the yield increases for the non-protected systems results in a decrease in the energy per tonne of class 1 fruit relative to the protected systems such that energy efficiency is greater.
The organic systems that applied fewer crop protection treatments and used products that contained either plant extracts or sulphur had the lowest associated environmental risk. For the non-organic systems the potential risk to the environment from pesticide use either via environmental pollution and/or direct impacts on wildlife were greater than for crops such as winter wheat and sugar beet but lower than potatoes. The fumigant chloropicrin was the greatest single contributor to the overall risk.
The risk of loss of nitrogen from the soil into the groundwater is likely to be small for most soil grown crops since the nitrogen requirement is low and the majority of nutrients are applied to the beds only, through the irrigation system during the summer months when the crop is actively growing. The presence of water impermeable barriers that prevent the infiltration of rainfall into the areas where nutrients are applied is likely to reduce the risk further. The fallow non-cropped alleys may lose some nitrogen but this will be dependent upon the existing nitrate content of the soil since no further nitrogen will be applied to these areas that will in turn be dictated by the previous crop. The greatest losses of nitrogen to the environment were in some of the organic systems that applied farmyard manure. The risk is increased on account of application of the fertiliser to the entire production area, alleys inclusive, as opposed to the beds alone as for the integrated systems.
In relation to crops such as sugar beet, the water requirement of strawberries is greater, 1546 – 2299 m3/ha compared to 500 m3/ha, however it is delivered with more efficiency. The water is applied directly to the roots beneath an impermeable plastic mulch using trickle irrigation in most systems which does not allow significant losses from evaporation to occur compared to, for example, a high pressure boom sprayer. The risk of soil erosion within strawberry crops is low, mainly as a result of the cover on the soil surface provided either by the polyethylene mulch on the beds or straw within the alleys. The increased run-off from drainage from polytunnels poses the greatest risk although this may only be to a limited number of alleys on account of most being under the cover of the tunnel. The presence of straw mulch within the alleys for most crops however, greatly reduces this risk of surface run-off.
An economic return on strawberry crops, unlike many arable crops, will in all probability require two or three years after initial investment in materials is made. Some systems may have a negative margin during the first year on account of the high establishment costs but the margins will increase for all crops when taken on to a second year, particularly if they are soil grown. The use of protection is costly but the improved yields repay the initial outlay. The organic crops command a higher price per tonne with fewer inputs so despite low yields in those that did not supplement soil nutrients with FYM, margins remained high. The majority of labour for strawberry crops is casual, that is temporary and mostly obtained from outside the local community thus the local employment opportunities associated with strawberry production represent a small proportion of the overall labour input. The labour requirement drawn from the local community for strawberry production is however probably greater than for other crops such as, for example, cereals.
The systems that produced the greatest overall sustainability profile per area of crop were those with the fewest inputs of energy, nitrogen, phosphorous and water and the smallest outputs of greenhouse gas emissions, nitrate and soil loss. They included those organic systems that did not apply farmyard manure and the integrated systems that did not use protection or fumigation. The protection and fumigation of crops improves yields thus although the performance per ha of some systems was high, the lower yields meant that per tonne of class 1 fruit, the inputs were actually increased and consequently the overall performance reduced. A balance must be achieved between minimising inputs to the system overall while maintaining reasonable yields so that per tonne of class 1 fruit produced, environmental inputs and outputs remain low. Of the systems examined, the protected organic crops and the summer planted integrated systems maintained reasonable yields despite fewer inputs. The summer planting of crops achieves an improved yield during the first cropping year relative to the spring planted crops but inputs do not tend to increase greatly.
Project Report to Defra8. As a guide this report should be no longer than 20 sides of A4. This report is to provide Defra with
details of the outputs of the research project for internal purposes; to meet the terms of the contract; and to allow Defra to publish details of the outputs to meet Environmental Information Regulation or Freedom of Information obligations. This short report to Defra does not preclude contractors from also seeking to publish a full, formal scientific report/paper in an appropriate scientific or other journal/publication. Indeed, Defra actively encourages such publications as part of the contract terms. The report to Defra should include: the scientific objectives as set out in the contract; the extent to which the objectives set out in the contract have been met;
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details of methods used and the results obtained, including statistical analysis (if appropriate); a discussion of the results and their reliability; the main implications of the findings; possible future work; and any action resulting from the research (e.g. IP, Knowledge Transfer).
Abstract of the research proposalThe main objective of this proposed project is to apply current state-of-the-art environmental impact and
economic and socio-economic assessment techniques to a range of strawberry production scenarios to develop a better understanding of the sustainability of the UK crop.
The desire for agricultural sustainability is well recognised in the UK’s agricultural industry and is now accepted by most farmers, although the means for delivering such a goal are still largely unclear. This is, in-part, due to the lack of sound data describing just how far away that goal is. Whilst we have fairly reliable data on the farm economics of crop production, its environmental impact (considering the production cycle overall) is less well defined. It is only now with the development of risk assessment techniques and sophisticated models mapping environmental fate, that we have the skills to address this problem. Bringing economic appraisal together with environmental impact assessment will allow more informed judgements to be made on any possible socio-economic impacts and so lead to a better assessment of the sustainability of UK food production.
This project will provide information that will assist in the development of inherently more sustainable production systems which remain economically viable. This reflects the governments policies and aims for efficient and competitive agricultural and horticultural systems that sustain and enhance the environment.
Purpose from the research proposalWithin the horticultural sector the message regarding sustainability is not as firmly in place as other sectors
and an effort needs to be made to promote the concept. The UK strawberry crop is currently considered to be worth around £79m (2001), with around £45m of additional strawberries being imported (during 2000/2001) and just £0.56m being exported. UK strawberries are prized by consumers for their quality and taste. However, the sustainability and environmental impact of all UK food production is of serious concern to both regulators and consumers, so in order to protect the UK market long-term, sound information on the sustainability of UK strawberry production is needed.
Strawberries are grown throughout the UK with the highest concentration, ~28%, in the South East; ~22% in the East; 20% in the Midlands and the West account for around a further 20%. Organic strawberry production only accounts for around 0.02% of the UK crop. Minimising pesticides remains a priority for the industry. Approximately 55,600 spray hectares of pesticides are applied which amounts to around 11 spray rounds per crop. Approximately, 170 tonnes of nitrogen are applied annually to the UK crop, low compared to most agricultural crops. Energy and water requirements, and waste production (packaging, waste crop etc.) could all be high, however, as yet detailed information is not Lewis widely available. Previously, little work has been done to compare management practices with respect to understanding their potential for environmental impact and progress towards sustainability.
Environmental impact assessments (EIA) are often used to aid decision-making on complex planning issues and the use of such techniques within agriculture is about to come of age. Sophisticated risk assessment methods are now available for planning pesticide strategies (et al., 2003) and mathematical models have been developed which simulate the nitrogen dynamics within soil systems to generate field specific fertiliser recommendations and to predict environmental losses (Smith et al., 1996). In addition, energy budgeting techniques have been published in the scientific press (Hülsbergen and Kalk, 2001). However, with the exception of work done on the sustainability of sugar beet production, few studies to date have attempted to draw together these techniques to quantify the environmental impact of a specific crop.
This project seeks to compare a range of strawberry production methods in a variety of geographical locations (including Europe albeit to less depth) using state-of-the art EIA and socio-economic techniques to provide a better understanding of the sustainability of the UK strawberry crop. This will provide DEFRA with data for policy development and provide the industry with best practice guidelines for progression towards sustainability.
Scientific Aims and Objectives from the research proposali) Support DEFRA policy on the promotion of more sustainable crop production, especially that which relies on the minimisation and optimisation of crop production inputs (such as pesticides) in order to minimise environmental impact and protect natural resources.ii) Utilises previously funded DEFRA research to provide sound data for future planning and policy issues.iii) Acts as a model for further crops.iv) The UK strawberry industry will be provided with detailed information on the sustainability of its crops and its strengths & weaknesses.v) Help formulate best practice guidelines.
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2.0 Methods2.1. Strawberry production systems
A grower questionnaire, devised by East Malling Research, obtained detailed descriptions from 20 growers of the most typical methods of strawberry production in the UK (Table 1). Differences included the use of soil fumigation, protection with polytunnels, organic production and whether soil or media grown. Typical outputs with respect to class 1 fruit per ha for each system and soil type were also provided (Tables 1 and 2). A total of 14 production systems were identified, with six additional sub-systems to give a total of 20 variations in all. All systems produced between one and two crops with the exception of Systems 1, 2 and 4 which produced up to three crops. Yield data and fertiliser regimes from individual growers are given in Appendix Tables 1 – 3.
Three geographical locations were chosen from key strawberry growing areas with variation in weather patterns, soil type and groundwater vulnerabilities. They included the South-East (1006 ha) represented by Kent (59 % of production within the South East region), the East of England (602 ha) represented by Norfolk (55 % within the East of England region) and the West Midlands (512 ha) represented by Herefordshire (62 % within the West Midlands region).
Production occurred on a range of soil types (sand, ‘other mineral’ and clay) and within different rainfall areas (low, moderate and high). Three descriptions of local wildlife habitats in and around strawberry enterprises in the three example locations were identified during visits to growers to incorporate sensitive habitat features such as surface water, woodland and species rich hedgerows as follows:i. relatively benign - no surface or running water, single species hedge/windbreak with little or no ground flora.
Bare soil field margins. No artificial drainage. ii. standard - surface water present part of the year (drainage ditch, 1 m wide, 0.1 m deep for 50% year), gappy
mixed species hedgerow with ground cover 60% of field boundary, a few but mostly 2 - 3 dominant species of flora. Vegetated field margins 1 m wide. No artificial drainage.
iii. relatively sensitive - surface water all year (pond, 3 m wide by 0.5 m deep) and/or mature mixed species woodland with diverse ground flora adjoining 30% of field boundary, mixed species hedgerow with ground cover 60% of remaining field boundary. Vegetated field margins 3 m wide. Sub-surface field drains.
2.2. Energy balance
The energy balance was based on the technique described in Hülsbergen & Kalk (2001) and considered the input of fossil energy into the system. The input from manual labour and from the sun was not included. The energy requirements up to and including storage within the coldstore for each production system (expressed as megajoules per hectare (MJ/ha)) is divided into four sections: crop protection, nutrition, cultivations and culture. The sub-sections are further divided by i. energy for the manufacture of crop protection chemicals, fertilisers, plastic and steel for tunnels and mulch
(including packaging and transport to the farm). Materials such as plastic tunnel covers whose lifetime is longer than one season were assigned manufacture energy values on a per year basis.
ii. energy required for carrying out of field operations. Each operation was assigned a value based on the type and working width of machine and in the case of tillage operations, the operating depth and soil type.
iii. indirect energy (the energy required for the manufacture of machinery and its maintenance). The operating lifetimes and depreciation periods of the machines were as described by Hülsbergen & Kalk (2001).
iv. the energy costs for transport of the crop from the farm to retail outlets. The sub-divisions were combined to give an overall estimate of total energy requirement per hectare, and to
give an estimate of energy input per tonne of class 1 strawberries harvested. A more detailed description of the methodology is given in Appendix 1.2. and Appendix Tables 8 - 14.
2.3. Global Warming PotentialThe global warming potential (GWP) associated with the combustion of fuel for machinery operation and for
product manufacture were derived from the Carbon Trust (2004). Refer to Appendix 1.3 and Appendix Tables 13 – 14 for a more detailed description.
2.4. Nitrogen loss to leaching and denitrificationTwo environments exist at the ground level within most strawberry crops, fallow soil within the alleys and
soil protected by a polyethylene mulch in the beds. The fallow soil within the alleys will be protected when a polytunnel is erected.
2.4.1. Nitrogen loss from soil between rows. The loss of N from the fallow alleys between beds was simulated using SimUlation of Nitrogen Dynamics In Arable Land (SUNDIAL) (Smith et al., 1996), developed at IACR-Rothamsted, to evaluate the risk posed by strawberry production to the contamination of ground water with nitrate leaching and global warming potential (GWP) by nitrous oxide (N2O) emissions from de-nitrification. It is estimated that 3.5% of denitrified N is lost as N2O (de Vries et al., 2003). Refer to Appendix 1.4.1 for a more detailed description.
2.4.2. Nitrogen loss beneath mulch. Nitrogen leaching beneath the mulch may result from the application of irrigation water, in which nutrients are contained, in sufficient quantities that water and N not utilised by the crop percolates through the soil profile and into the groundwater. The irrigation water is applied to the beds only and delivered close to the plant roots over a period of up to 22 weeks (grower interviews) for 30 minutes per day (East Malling Research farm, pers comm) although this period may vary between growers. Water uptake by the crop
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relative to water delivered through irrigation could not be calculated with confidence since water is applied to maintain a percent of field capacity as opposed to in response to specific plant requirements (D. Simpson, pers comm). The N at risk to leaching beneath the mulch was calculated as the N applied minus the N uptake by the plant (fruit and vegetative parts) based on the yield data provided by the grower interviews and macronutrient partitioning data from Lieten and Misotten (1993). Refer to Appendix 1.4.2 for a more detailed description.
2.5. Nitrogen and Phosphorous balance and nutrient re-cyclingFor soil grown crops, most growers stated that nutrients were applied through the irrigation system during
the summer based upon leaf analysis with few that applied N as a base dressing, in which case the quantity of nutrients applied were adjusted to Defra recommended levels based upon soil analysis. As a result, exact figures could not be provided since the N is applied as required. Some growers provided actual figures while some were estimates (Appendix Tables 2 - 3). Nutrient application rates to soil grown integrated cops were taken from the MAFF (2000) Fertiliser Recommendations. Those strawberry crops grown in rotation tended to include winter wheat thus for a preceding crop of winter wheat, the Soil Nitrogen Supply (SNS) index will be 0 or 1 in most regions, or 2 on other mineral soils in low rainfall areas such as East Anglia. On clay or other mineral soils, the recommended N application rates are 40 and 50 kgN/ha for Junebearer and everbearer crops respectively. Refer to Appendix 1.5 for a more detailed description.
An overall nutrient balance, one that includes all inputs (fertiliser, atmospheric deposition, biological fixation) and outputs (offtake in harvested crop, loss to leaching) provides an indication of nutrient use efficiency by the crop and the risk of nutrient loss after its removal. Three main types of nutrient budgets are described by Watson et al (2002):
i. Gate budgets that record the flow of nutrients entering and leaving the system but do not include uncontrollable inputs such as biological fixation or atmospheric deposition.
ii. Surface budgets that take account of differences between the total inputs and removal in the crop and include uncontrollable inputs. They do not however give details of the fate or origin of any nutrient surplus, that is, presence within the soil or loss from the system.
iii. System budgets that provide a greater level of detail on inputs, outputs and internal flows and give additional details for the location of nutrients such as in the soil, crop etc.
The current study attempted a System budget for N and included atmospheric deposition of 30 kgN/year (Goulding et al., 1998ab) and biological fixation by free living soil bacteria of 5 kgN/ha/year (Goulding et al., 1990) in addition to controllable fertiliser N inputs and N contained within the planting material. Fate of N to leaching and de-nitrification were taken from section 2.4 for each production system. Uncontrolled inputs of P were assumed to be negligible (Berry et al., 2003). Refer to Appendix 1.5 for a more detailed description.
The recycling of nutrients from organic sources or from previous fertility building crops may also be considered a measure of sustainability. The percentage of nutrients supplied by non-mineral fertiliser was calculated for each system.
2.6. Water useThe total water use (m3/ha/crop) was calculated from the quantity of irrigation stated in the grower
interviews and categorised by use of protection and growing media (Appendix 1.2.4). Further water use from the application of crop protection products was assumed as high volume drench 2000 l/ha, high volume 1000 l/ha, medium volume 500 l/ha and low volume 375 l/ha. The pest and disease programme was provided by ADAS and the herbicide programme by the East Malling Research farm (Appendix Tables 4 - 7).
2.7. Ecotoxicity from pesticidesGrowers referred to the use of either methyl bromide or chloropicrin as a fumigant. Since methyl bromide
is being phased out and its current use is restricted, chloropicrin was examined. The pest, disease and herbicide programme described in section 2.6 was assessed to identify any potential risks to non-target fauna and flora. The application dates assessed are purely a guide and it is acknowledged that in reality there will be flexibility within the dates depending upon whether the crop is brought forward using fleece or delayed using deep straw. Much of the programme begins at first flower and recommendations are given for the following crop protection applications based on a number of days elapsed afterwards. Variation in the time of first flower will result in variations in the dates of the application of crop protection products, thus the dates given in Appendix Tables 4 - 7 are purely a guide. Most growers stated that the use of protection reduced the number of sprays for Botrytis and that biological control agents such as Phytoselius were used whenever possible. Organic producers depend upon tunnels for Botrytis reduction, non-protected organic crops do not yield at sufficient levels to be deemed viable. They stated the natural regeneration of weeds within the alleys enhanced beneficial insects that act as natural bio-control agents, while nematode sprays or plant extracts with insecticidal properties such as Majestik® were used in addition to sulphur as a fungicide for mildew. Weed control with herbicides was limited to the alleys only with additional weed suppression from the application of a straw mulch, a plastic mulch was used for weed suppression in the beds. Each scenario was modelled using the p-EMA software (Lewis et al., 2003) for three different strawberry growing locations in the UK (East Anglia, the South East and the West Midlands) with three different environments. Refer to Appendix 1.6 for a more detailed description.
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2.8. Soil erosionThe risk of soil erosion (t/ha) for the duration of each crop was calculated using the Universal Soil Loss
Equation (USLE) (Wischmeier and Smith, 1978) and the Revised Universal Soil Loss Equation (RUSLE) (Renard et al., 1997). An overview of the methodology and assumptions for its adaptation to UK strawberry crops is given in Appendix 1.7.
2.9. Net marginThe net margin of each strawberry production system was calculated as described in Tzilivakis et al
(2004) by subtracting the variable costs (of planting material, agro-chemical sprays, fertilisers and contractors services and the costs for cultural operations) from the output provided by the sale of class 1 fruit. The values for agricultural products and field operations were obtained from Nix (2004), The Agricultural Budgeting and Costing Book (ABC) (2004) and from Lampkin et al (2004). Additional costs for agro-chemicals were obtained from East Malling Research farm and contractors. The costs associated with strawberry production are summarised in Appendix Tables 18 and 19. The grower interviews found variation in the planting rate/ha although no correlation between system, planting type and rate was evident. The current study used the recommended planting rates for each planting type in the margin calculations.
Yield data was provided by the grower interviews and averaged by system and soil type. Most growers stated that they only sold class 1 fruit although Lampkin (2004) allows for 30% class 2 fruit to be sold for processing at a reduced price. Yields within systems, particularly System 1 were variable and the output per tonne is given based on system and soil type although it should be noted that in many cases only one set of grower yield data was available at this level of classification. The value of crop output per tonne of Class 1 fruit was calculated as £1750/t for integrated crops (ABC, 2004) and £4000/t for organic crops Lampkin (2004). Premiums are available for very early produced crops (for example, late April and early May) that results in lower yields thus output per tonne of Class 1 fruit may be greater than the £1750/t cited from ABC (2004).
2.10. Local employmentLabour was classified as grower, contractor or casual and the labour input (hours/ha) for each operation
was taken from Nix (2004), ABC (2004), the grower interviews and quotes from contractors (Appendix Table 20). Local employment is most likely to be in the form of core farm staff or local contractors (classed as grower labour). Grower labour was assigned to operations such as cultivation of the seedbed, the spraying of agro-chemicals and the construction and maintenance of tunnels after receiving training from the tunnel supplier with additional support from casual staff at a ratio of 1 farm staff to 3 casual staff. Specialist contractors carried out the fumigation of the seedbed. Seasonal casual labour was required for labour intensive operations including planting, de-runnering and harvest. The total hours of local employment derived from the outlined classification of labour input was calculated for each system and used in the construction of sustainability profiles.
2.11. Visual impactThe visual impact of polytunnels, tables and plastic mulch were assessed with the adaptation of the
scoring of impacts based on qualitative data analysis techniques outlined by Mason (1996). Using ordinal level measurement, mulch and polytunnels were assigned a score per week of presence as outlined in Appendix 1.4.1 while tables were present for every week during the year: mulch score = 1, table score = 1 and polytunnel score = 5.
2.12. Calculation of Performance IndicesThe performance indices were calculated using the method described in Tzilivakis et al (2004). Each
parameter for each system was indexed as a fraction of the maximum value (0 to 1). Those parameters in which the smallest figure is desirable (GWP, energy efficiency, leaching, denitrification and pesticide ecotoxicity) the inverse is calculated (i.e. 1 minus the fraction of the maximum). For second year crops the total input / output per ha for the two years is divided by two to give an input / output per crop per ha (ie cannot have a second year crop without the first year). A direct comparison between fruit produced for one crop and the fruit produced by two crops combined can be made and any improvements associated with the additional crops will be clearly illustrated. The overall output for third year crops is totalled for three years and divided by three. The output per tonne of class 1 fruit is the total inputs for each year combined divided by the total yield for each year combined (eg years 1 and 2 for second year crops). The greater the overall indices, the higher the performance of a particular system for the parameters considered.
2.13. Weighting of Performance IndicesEach parameter was further weighted based on likely scale of impact. Impact at local scale only had a
weighting of 1 (the indices for each parameter were multiplied by 1), at a regional scale a weighting of 2, at a national scale a weighting of 3 and at a global scale a weighting of 4. Energy use and GWP were considered to impact at the global scale so were weighted by a factor of 4, nutrient balance and nitrogen leaching at the catchment (regional) scale so weighted by a factor of 2. The ecotoxicity measured the impact within the field and field margins (local scale) but the impact of population fragmentation may extend to the regional scale so a weighting of 2 was assigned. Nutrient re-cycling was weighted at the local scale as was soil erosion. Water use was considered to impact at the catchment (regional scale) (weighting of 2). Net margin contributes to Gross
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Domestic Product (national scale) so was assigned a weighting of three while local employment and visual impact were considered to impact at the local scale (weighting of 1).
2.14. Spanish productionSpanish strawberry crops were compared with those in the UK using the methods, where relevant, as
outlined previously for UK crops. Spanish strawberry crops are winter as opposed to spring sown. Most are fumigated, protected crops (mostly with polytunnel but also with micro-tunnel) grown for one year without rotation on sand soil. Bed preparation, the application of black plastic mulch and soil fumigation occurs in September and planting takes place during mid October. A base fertiliser dressing may be applied although much of the nutrients are delivered through fertigation. The crop is irrigated for up to 0.5 hours per day mostly using an automated process although the soil moisture deficit is not monitored. Water is abstracted from reservoirs adjacent to cropping areas. Harvest begins in late January / early February until the end of May. Harvesting occurs every 7 - 10 days initially, every 4 days during April and every 2 - 3 days during May. The planting of two varieties with different fruiting periods staggers production and extends the season. The main varieties are Camarosa (75%, fruits from January onwards), Benthano (15%, fruits from February onwards) and Lanassa (6-7%). Container crops occupy a smaller hectarage but peat or coir container crops may also be used.
The Spanish growers stated EUREPGAP membership that restricts agro-chemical application to two herbicide applications per crop. Disease treatments include mainly Botrytis and mildew. Increased insecticide sprays for aphids and cyclamen tortix moth may be required relative to UK crops however, since many Spanish growers supply UK supermarkets the same restrictions on the usage of crop protection products apply. In general vegetation is sparse and margins consist of bare soil and are used for vehicle access. Neighbouring growers are devoted to 100% covered production and surround each farm in most cases thus little fauna and flora are present, drainage ditches with water present during the winter separate individual growers land. A few small scale growers away from the main production area have sensitive habitats, namely mixed species woodland, adjacent to production areas. An increased haulage distance of 2165 km (Huelva to Dover) using refrigerated transport relative to UK produced crops is required with additional fuel for an unrefrigerated return journey if the vehicle is empty.
3.0. Results3.1. Energy
The input per ha for one crop (excluding harvest and post harvest operations) ranged from 15.8 – 168.3 GJ/ha (Appendix Figure 1). The majority of inputs were from plastic manufacture for polytunnels, mulch and irrigation pipe and from the manufacture of soil fumigants. The delivery of an additional 750 m3/ha of irrigation water in protected crops required an estimated additional 0.2 GJ/ha for trickle irrigation. For Junebearer crops, the system with the lowest input (System 4, no crop first year), comparable to that of an arable crop, did not use fumigation, protection, polyethylene mulch or irrigation. Other non-fumigated non-protected crops such as system 4, the non-protected organic system and the non-protected container crop on raised beds also had lower energy inputs/ha, between 41.1 and 58 GJ/ha. The greatest input/ha for one crop was in the protected crops on account of the inclusion of energy associated with the manufacture of materials for polytunnel construction. The energy associated with a non-protected crop protection programme was 0.4 GJ/ha greater than for protected crops, while a maincrop programme increased the energy input by 4.5 GJ/ha relative to the 60-day programme. Soil fumigation with chloropicrin at 400 l/ha required an additonal 38.2 GJ/ha. The summer planted protected fumigated crops on clay soil had the greatest input/ha owing to the increased energy costs associated with bed preparation (989.8 MJ/ha) and the additional energy costs for crop protection for an over-wintered as opposed to spring planted crop for one crop. The crops were not protected during the second year thus the energy requirement for two crops decreased when the polytunnels were excluded. The organic crops had few inputs associated with crop protection and for the crop that did not apply FYM, there was no input for nutrition. The energy required for the loading, transport and application of 40 t/ha of FYM relative to the energy associated with the manufacture of mineral N, P and K in the integrated systems was 5.7 GJ/ha compared to 4.3 GJ/ha for one crop. The mineral fertiliser is added to each crop thus for two crops, nutrition for integrated crops is 8.5 GJ/ha while the organic crops with FYM remain at 5.7 GJ/ha. The growing of a second or third crop reduces the energy input per crop in all soil grown systems, or container crops on raised beds, to 11 – 127.2 and 9.2 – 115.2 GJ/ha respectively (the summer planted protected crops are not protected in the second year thus the maximum value is taken from the protected System 1). The energy inputs associated with bed preparation, fumigation and polyethylene mulch that last the lifetime of the crop are shared between the additional crops. The table grown crops do not require operations that last the lifetime of the crop but tend to incur inputs more or less equally each year thus the coir table grown system 9 has the greatest input per crop when averaged over two crops. Container crops grown on raised beds required less energy for one and two crops on account of the less plastic associated with bags relative to mulch although if the mulch is used for a third year the energy input per crop are similar. The energy associated with crop nutrition was greater in the container systems, in particular the coir crops, compared to the soil grown crops. The coir systems also required a greater input for the shipping of the media from Sri-Lanka that also requires fumigation before export. Overall, this was not as great as the energy input associated with the fumigation of one crop in soil grown protected fumigated systems however per crop for two crops it is greater. The everbearer crops followed a similar trend to Junebearer crops with protected fumigated systems requiring the greatest inputs (164.6 GJ/ha) then the table grown coir systems (148.3 GJ/ha) for one crop
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(Appendix Figure 2). The lowest inputs were in the non-protected fumigated soil grown crop (98.5 GJ/ha) and as with the Junebearer soil grown systems, reductions in energy input per crop were observed per crop for two soil grown crops.
The recycling of plastics offers potential to reduce the manufacture energy of polyethylene to on average 31.5 MJ/kg (BPI, 2004). If the polyethylene for tunnels and mulch is assumed to be recycled after use and / or manufactured from recycled material within a recycling chain of four products then the inputs may be reduced to 15.4 – 135.2 GJ/ha for one crop (Appendix Figures 3 and 4). A small reduction is observed for System 4, no crop first year as a result of recycling pesticide containers and fertiliser bags. The input per crop may be reduced to between 10.8 – 99.5 and 9.1 – 89.3 GJ/ha/crop if taken on to a second or third crop respectively.
The energy input per tonne is greatly reduced in all soil grown systems for two and three crops on account of greater yield for second and third crops in most systems and the reduction in energy input per crop as described previously (Appendix Figures 5 and 6). In general, the higher yields associated with the first crop under protection (System 3) decreased the energy input per tonne of class 1 fruit relative to a non-protected crop (System 4), from 10.3 to 8.2 GJ/t. The energy efficiency associated with operations common to both systems such as mulch and bed preparation are improved in the higher yielding protected crops. For two crops however, improved yields in System 4 during the second year relative to System 3 resulted in a lower energy input, 5.5 GJ/t compared to 7.1 GJ/t in the protected crop although reductions occur in both systems. The energy input in System 4 was reduced further for three crops, to 4.5 GJ/t. The fumigation of a crop did not improve yields sufficiently to increase the energy efficiency of fumigated (System 2) (13.1 GJ/t) relative to a non-fumigated crop (System 4) for one crop. Yields improved for two crops in the fumigated System 2 to give an overall energy input of 6.3 GJ/t for two crops although the input remained slightly lower, 5.5 GJ/t, in the non-fumigated System 4. An exception to this was the summer planted non-protected crop that yielded as a maincrop during the first year with an associated input of 5.0 and 3.8 GJ/t for one and two crops respectively. Direct yield improvements associated with fumigation are likely to be site specific and can only be quantified precisely if a fumigated and non-fumigated crop were grown on the same site then compared directly. Yields were not available for non-fumigated summer planted crops. The use of protection and fumigation combined (System 1) varied considerably on account of the variation in yields within this system. The yields on mineral soils had an increased energy input per tonne, 13.6 GJ/t, relative to the non-fumigated System 4 (10.3 GJ/t) while on clay soil it was reduced to 9.8 GJ/t. The energy input was reduced to 8.5 and 7.2 GJ/t for two crops on clay and other mineral soil respectively, still greater than the 5.5 GJ/t for System 4. Protected crops appeared to have a greater energy input per tonne for two crops, mainly since the energy input associated with the polytunnel was calculated on a per year basis as opposed to for the crop lifetime that fumigation was. As with the non-protected fumigated System 2, summer planted crops improved the energy efficiency further, a reduction to 9.7 and 7.4 GJ/t on other mineral and clay soils respectively. These crops were not protected during the second year thus the energy associated with polytunnels eliminated. Per tonne for two crops, inputs were 7.2 GJ/t, similar to the protected System 1 on clay soil (7.2 GJ/t) although lower than that on mineral soil (8.5 GJ/t). The organic protected crops varied in yield and thus energy input per tonne depending upon the application of FYM. The crops to which FYM was applied had a slightly greater input per tonne than a protected non-fumigated integrated system (System 3), 8.6 compared to 8.2 GJ/t. This was greatly increased in the organic crop that did not apply FYM, 11.8 GJ/t on account of the reduction in yield. The inputs decreased for two crops in both fertiliser regimes, to 10.1 and 6.8 GJ/t for non-FYM and FYM respectively. The energy input per tonne in container crops were smaller for one crop than for the soil grown non-fumigated systems. Table crops had a greater energy input on account of the materials required for table construction although as stated previously, an exact value is difficult to quantify. The protected peat systems had the least input per tonne, 7.0 – 7.8 GJ/t, although a similar figure was obtained for non-protected peat crops on raised beds. Coir crops that required greater volumes of mineral fertilser had increased inputs of 8.3 and 9.2 GJ/t on raised beds and tables respectively. Smaller reductions in input per tonne for two crops relative to the soil grown systems were noted for container crops. Yield improvements occurred in the non-protected peat and protected coir systems but energy input was only decreased per crop for the preparation of raised beds. The energy input for protected peat container crops on raised beds (6.9 GJ/t) remained lower than non-fumigated protected soil grown crops (7.1 GJ/t) on account of slight yield improvements although it may be greater for table crops (7.9 GJ/t) and in coir table crops (8.0 GJ/t). The input per tonne was reduced in all systems but in particular the protected systems if plastic is recycled (Figure 7).
The non-protected fumigated everbearer crops (System 11) on ‘other mineral’ soil maintained similar yields (20 t/ha) relative to the protected everbearer crops (System 10) (23 t/ha on ‘other mineral’ soils, 30 t/ha on clay soils) and thus had a lower energy input, 6.1 GJ/t, compared with the 8.5 GJ/t for protected crops on ‘other mineral soils’ (Appendix Figure 6). For two crops, yield improvements occurred on ‘other mineral’ soils for the protected crops and energy input decreased (7.9 GJ/t) however the inputs remained lower in the non-protected System 11 (4.9 GJ/t). No yield data was available for non-protected crops on clay soils. Protected organic crops on clay soil had an input of 7.5 GJ/t for one crop, slightly lower than the input for protected crops on ‘other mineral’ soils although greater than those on clay soils.
Post harvest energy input was directly proportional to yield and calculated at 1.3 GJ/t of which 1.1 GJ was attributed to plastic manufacture for the punnets. The recycling of plastic from polytunnels, mulch, bags, pesticide containers and fertiliser bags offers potential to reduce the energy associated with plastics manufacture and thus the overall input, particularly in protected systems (Appendix Figures 7 and 8). The recycling of plastic punnets
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may reduce post harvest energy inputs to 0.9 GJ/ha. Inputs per tonne were reduced to between 1.6 and 10.9 GJ/t for first year crops and 1.5 and 6.6 GJ/t for second year crops.
3.2. GWPThe GWP for each system followed similar trends to energy use with the exception that those systems
that required greater inputs of N fertiliser, namely the container systems, that had an increase in GWP/ha. The GHG pre-picking (eq tCO2/ha) were greatest in the coir protected table container grown systems for both Junebearer (7.2 eq tCO2/ha) and everbearer crops (8.0 eq tCO2/ha) (Appendix Figures 9 and 10). The protected peat container Junebearer crops had greater GHG emissions (5.5 and 5.3 eq tCO2/ha on tables and raised beds respectively) compared to the protected non-fumigated System 3 (5.1 eq tCO2/ha). A reduction per crop for second year crops did not occur in the container systems as it did in the soil grown systems. As with energy input, the GHG emissions per ha were lowest in the soil grown crops that did not use protection or fumigation. De-nitrification was low for most systems and as a result contributed a relatively small proportion of the GHG emissions for each system. The application of FYM to organic Junebearer crops during the summer and organic everbearer crops during the spring increased N losses to denitrification relative to the crops that did not receive FYM, particularly for the first crop after application. (Appendix Figures 11 and 12). The protected peat container crops (System 8) had slightly higher GHG emissions than the non-protected non fumigated soil grown System 4 on account of greater inputs of mineral N. The GWP for each system was reduced if polyethylene is recycled (Appendix Figures 13 and 14).
The GWP per tonne, including post harvest operations, was least again in the System 4 (no crop first year) and greatest in the fumigated protected system on mineral soils although as with energy use, the GHG emissions per tonne for second year crops are reduced (Appendix Figure 15). The GHG emissions tended to be lower in the protected crops relative to the non-protected crops for one crop. A greater proportional increase in yield for second crops relative to the first crop in the non-protected systems resulted in fewer GHG emissions per tonne for two crops compared to protected crops. The GHG emissions per tonne in Junebearer peat container crops tended to be similar per tonne to the soil non-fumigated crops during the first year however emissions are greater for two crops. Coir Junebearer container crops had greater emissions than non-fumigated soil crops during both years although they were lower than the fumigated crops on mineral soils for one crop (Appendix Figure 16). The high yielding everbearer protected coir system 14 resulted in lower GHG emissions per tonne for one crop than the soil grown protected integrated and organic crops although emissions were least in the non-protected fumigated soil grown system.
3.3. Nitrate leachingThe greatest risk of N leaching is from second year organic crops (Appendix Figures 17 and 18) to which 40
t/ha FYM is applied to the entire seedbed, alleys inclusive, although recommendations of 25 t/ha by Lampkin et al (2004) reduce losses by between 8.6 and 13.6 kgN/ha for protected organic Junebearer and everbearer crops respectively. Nitrate leaching from the alleys was predicted to be low for soil grown integrated Junebearer crops (4.8 – 14.8 kgN/ha) with the greatest risk during the fallow period after cultivation of the seedbed before planting. Additional losses beneath the mulch may occur in the lower yielding non-protected and non-fumigated crops on account of an N surplus of up to 14 kgN/ha not removed by the crop. Leaching may be slightly greater in the alleys of container crops on raised beds, up to 21.9 kgN/ha, where a greater area of the soil is exposed to rainfall. The container systems receive a greater quantity of nutrients than soil grown systems although this is applied to the substrate within the container. A proportion of this may be lost from the container in excess irrigation water, the risk increased with increased application time. Any nutrients lost will however have to infiltrate the soil profile beneath the bag before entering groundwater so nutrients lost form bags are unlikely to be leached immediately. The greater quantities of N applied to container crops, coir substrate everbearer crops in particular, on raised beds may cause an increased risk especially if irrigation periods are increased and the risk of water loss from the containers increased. If 10 % of the nutrient surplus within the container are assumed leached the coir grown systems for both Junebearer and everbearer systems may leach an additional 12.6 and 15.6 kg N/ha respectively. The period of time to which irrigation is applied may vary between growers, some may irrigate for periods of up to 4 hours per day where the risk of nutrient loss is likely to be increased on account of increased probability that nutrients will be carried below the root zone. Risk may also be greater in the organic crops that apply N in one application. System 4 (no crop first year) has the greatest leaching risk for the first crop on account of two years of nutrient loss combined (41.5 kgN/ha). The N losses from the alleys for the first crop for soil grown everbearer crops varied between 14.9 and 17.2, slightly higher than for the Junebearer systems on account of the greater period of time elapsed, until September or November, before the end of harvest.
3.4. Nutrient balance and percent nutrient recycling. For those growers that supplied exact nutrient application rates, no correlation between the rate and eventual
yield was evident although existing nutrient levels within the soil pre-planting are unknown. The estimated N surplus per crop for soil grown Junebearer crops was low, between 20.7 and 41.5 kgN/ha (Appendix Figure 19) on account of the small quantity of nutrients, 40 kgN/ha, applied. Similar observations were made for soil grown everbearer crops to which 50 kgN/ha was applied (Appendix Figure 20). The container systems, in particular the coir systems, to which 177 and 224.8 kgN/ha respectively were applied per crop had a greater N surplus and lower N use efficiency in comparison to soil grown crops. The organic crops to which 40 t/ha of FYM was applied
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received a total of 240 kgN/ha and had the greatest nutrient surplus, 209.3 kgN/ha per crop for the first crop although this is reduced to 104.8 kgN/ha for two crops since no additional nutrients are added during the second year. Those organic crops that do not apply additional nutrients had the lowest N balance, 9.2 kgN/ha, for one crop as a result of uncontrollable inputs such as atmospheric deposition and biological fixation. The surplus of P was least in soil grown Junebearer and everbearer crops, between 14.2 and 17.7 kgP/ha (Appendix Figures 21 and 22). As with N, the surplus was greater for container crops, 34.8 – 37.5 kgP/ha in Junebearer crops and 47.2 and 51.9 kgP/ha in everbearer crops. The organic crop that applied FYM had the greatest surplus, 59.5 kgP/ha for first year crops and 57.6 kgP/ha for two crops. It was lowest in the organic crops that did not apply FYM. The reduction of FYM application rate to 25 t/ha had an associated reduction in the N surplus of the organic crops to 138.9 kgN/ha and 36.7 kgP/ha. The organic systems were the only systems in which nutrients were not obtained solely from mineral fertiliser as evident in the integrated crops. The N surplus increased in all systems for second or third crops with the exception of the organic crops to which the nutrients were applied solely as a base dressing pre-planting. The N and P surplus per crop (average of crops one and two) decreased in most systems on account of increased yields in second or third crops.
3.5. Water use Water use was mostly from irrigation and differences were highlighted between protected or non-protected
systems and the type of growing media (soil, peat or coir). For soil grown systems, protected or non-protected, no correlation was apparent between the volume of irrigation water applied and the soil type or region although the number of examples was small. Most growers applied around 2400-2500 m3/ha to protected soil grown crops, irrespective of soil type. Two growers applied less, 1500 and 2000 m3/ha to crops on ‘other mineral’ soil. The mean application rate to clay soil for protected soil crops was 2442 m3/ha while to ‘other mineral’ it was 2169 m3/ha (Appendix Figures 23 and 24). The organic crops did not require as great an input for crop protection relative to the integrated systems on account of the limited number of sprays. Water use per tonne of Class 1 fruit was least in the system 4 (no crop first year) without irrigation (1.0 m3/t class 1 fruit) followed by the summer planted fumigated non-protected System 2 (58 m3/t class 1 fruit). Input was also low in the protected peat container systems (85 m3/t class 1 fruit) and the summer planted fumigated protected system 1 on clay (120.2 m3/t class 1 fruit). The higher yielding protected systems tended to require a smaller volume of water /t class 1 fruit despite the greater application rate relative to non-protected crops. The lower yielding non-fumigated non-protected system 4 required 243.9 m3/t class 1 fruit.
3.6. Pesticide ecotoxicityAll systems examined fell into the ‘best practice’ category on account of application on a ‘need to spray’
basis and the spatial targeting of sprays to the plants only that results in the minimisation of drift onto non-crop areas. Pesticide ecotoxicity ranged from 0 in the organic systems to 288 in the summer planted fumigated non-protected crops (Appendix Figures 25 and 26). The crop protection products associated with the maincrop regime carried a greater risk than for the 60-day programme with scores of 288 and 212 respectively for fumigated non protected crops. Non-fumigated non-protected crops had a score of 195 for the 60-day programme and 236 for the maincrop programme. The main contributor to the ecotoxicity scores was from the fumigant chloropicrin in addition to the insecticides pirimicarb and thiacloprid and the fungicide Elvaron Multi (tolylfluanid). Ecotoxicity risk was decreased by the presence of protection that reduced drift and the number of Botrytis sprays with scores of 238 and 288 for fumigated protected and non-protected systems respectively. A further reduction was noted for container crops that have slightly less risk to soil fauna associated with them since the substrate within the bags intercepts much of the pesticide and prevents its movement into the soil. The majority of active ingredients are toxic to aquatic organisms (Appendix Table 17), thus increased risk alerts occur where water is present throughout the year, particularly for non-protected crops.
The mean score for soil grown crops, both 60-day and maincrop regimes, was 207.5 and this is compared with other crops in Appendix Table 18. Only potato has a greater score with 230, crops such as sugar beet have a score of 35. The programme examined is a worse case scenario and some applications may not be required each year. Per tonne, the lowest scores were the organic crops (0) followed by the non-fumigated non-protected system 4 with no crop in the first year (5.58), then the protected container crops (8.0 – 8.7). The highest scores were in the non-fumigated non-protected system 4 (30.5) and the fumigated non-protected system 2 (26.2).
3.7. Soil erosionThe risk of soil erosion ranged from between 0.33 and 5.6 t/ha (Appendix Figures 27 and 28), categorised as
‘very low’ and ‘low’. The risk of erosion is reduced by the presence of ground cover, either as plastic mulch on the beds, as straw mulch within the alleys or from the crop itself. Soil erosion risk was lowest in the organic Junebearer systems that applied FYM on account of the incorporation of large volumes of organic matter into the upper layers of the soil that reduced the risk of soil erosion within the alleys during the winter of the first year. Since the crops are summer planted a mulch is present during the winter in addition to the organic matter. For most systems, the greatest risk occurs during the fallow period immediately after tillage, summer planted crops will have a plastic mulch present during the winter although straw may not be applied to the alleys until the spring. For each subsequent year after tillage, the risk of erosion decreases thus for second and third year crops and table crops the previous land use factor (PLU) is reduced. The greatest overall risk was for table crops that are not mulched or have organic matter incorporated. The rainfall will impact either unheeded or will drop from a
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height of 1.0 m from the edge of the table. The ground is not tilled thus erosion risk relative to freshly tilled land is greatly reduced. The erosion risk may increase with the use of protection in those alleys into which the water drains on account of the impact of water fall from the tunnel covers although the presence of straw mulch will dissipate the impact of water falling to the ground.
3.8. Net marginThe margins associated for an assumed mean yield in each system are given in Appendix Figures 29 and
30. It is notable that many of the integrated soil grown systems and container crops have a net margin deficit for the first crop. The margin increases for two or three crops, partially on account of costs for mulch, bed preparation and fumigation shared between more than one crop, and partially as a result of the improved yields for second year crops.
The additional capital cost of polytunnel is estimated at £4191.00 per year and running costs of £762.00 per year, with an additional construction cost of £1398.00 during the first year. Output is costed at £1750.00/t class 1 fruit thus for one crop a yield improvement of 11.6 t/ha equates to an improved output of £20,300.00 with an improved margin of £13,949.00. For two crops, the overall increased output of £29,925.00 provides an improved margin of £18,621.00. There is also the option of a premium for earlier crops. The cost of fumigation ranges from £265.00 (200 l/ha) – £530.00 (400 l/ha) /ha for half and full rate respectively. Yield improvements in the grower examples were 1.7 t/ha and 4.4 t/ha for one and two crops respectively, a margin improvement of £2445.00 and £7170.00. The summer planting of crops had the greatest yield improvements of the integrated soil grown crops for the first crop. The fumigated non-protected summer planted System 2 in particular, that did not incur costs for polytunnel construction and maintenance while it maintained good yields, had the greatest margin for the first crop (£532.21/ha) followed by the fumigated protected summer planted system 1 on clay (£297.53/ha). For two crops, margins varied between £2546/ha for the non-protected non-fumigated System 4 to to £16910/ha for the summer planted System 2. The largest margins were in the protected organic crops for both Junebearers and everbearers on account of the additional premium, £4000/t class 1 fruit (Lampkin et al., 2004) compared to £1750/t for integrated crops (ABC, 2004). Those that applied FYM improved yields greatly while the cost of the nutrients was negligible, the only costs incurred were for the spreading of the FYM. The greatest overall costs for inputs were for the protected container crops owing to increased costs of peat and coir growbags relative to plastic mulch in the soil grown crops. Many container systems were grown for one year only thus greater yields would be expected for the first crop relative to the soil grown systems. The mean yields did not differ greatly, 19 and 18 t/ha for protected peat and container crops respectively compared to 18 t/ha for protected non-fumigated soil grown System 3. Margins did not tend to increase as greatly in container crops on tables for two crops as for the soil grown crops or container crops on raised beds since costs were calculated for each crop. Yields remained the same for peat container systems while an increase to 25 t/ha was noted for the second crop coir system. As mentioned previously, the output does not take account of increased premiums for early crops, thus margins in some of the examples may actually be higher. The two examples of non-protected peat container crops (System 8) varied in yield between 11.9 and 24.5 t/ha for a total of two crops, the lower yielding example and the mean of the two did not appear to yield sufficiently highly to command a positive margin.
All everbearer crops had sufficiently high yields to obtain a positive margin for the first year of cropping. Everbearer crops in general had similar input costs as Junebearer crops with the exception of increased nutrition costs, the coir container crops in particular, although the yields were the largest of the systems considered at 28 t/ha. The margins for one crop in the integrated systems varied from £1368 in peat container System 13 to £11320 in the protected fumigated System 10 on clay soil. They were slightly lower for two crops on account of the slight decrease in yield. The organic crop had the greatest margin of £47,928/ha.
3.9. Local employmentHours of local employment, labour performed by the grower or core farm staff, for each system were greatest
for the first year crops (Appendix Figures 31 and 32) and were mostly for the erection and maintenance of polytunnels (97.8 hours/ha with additional input from casual labour). Thus protected crops tended to have the greatest grower labour requirement. Much of the other grower labour was associated with the application of pesticides, 51.8 – 53.7 hours/ha for integrated 60 day and maincrop programmes respectively. The greatest grower labour requirement for first year crops was for the protected and fumigated summer planted system 1 with the smallest for the non-protected organic systems that did not require large labour inputs for either polytunnel maintenance or crop protection operations (4.5 hours/ha).
3.10. Visual impactVisual impact from mulch varied between scores of 0 and 88 for spring and summer planted or second year
crops respectively. Tables that were present throughout the year had a score of 52/year, tunnels that were present for 12 weeks a score of 420/year. The system with the greatest visual impact were the summer planted and the table grown protected crops (Appendix Figures 33 and 34) that has mulch or tables present throughout the year with additional impact from tunnels. The unmulched non-protected system 4 (no crop first year) had the smallest visual impact followed by the non-protected soil grown crops.
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3.11. Sustainability profilesThe sustainability profile for each system per ha and per tonne is displayed in Figures 1 - 4. The system with
the greatest overall sustainability profile pre-pick per ha for a Junebearer first crop was the protected organic crop without FYM (System 5) and the non-fumigated, non-protected, non-mulched, non-irrigated system 4 (no crop first year), followed by the summer planted fumigated non protected system 2 (Figure 1). The organic crops perform well on different criteria to those integrated crops that performed highly, namely nutrient recycling, pesticide ecotoxicity, net margin and soil erosion. The organic crop to which no additional nutrients were applied also performed well with reduced N leaching and a low N and P balance in contrast to the organic crop with 40 t/ha FYM that had the largest N and P surplus of the systems considered. All soil grown crops improved their sustainability profile per crop with a second or third crop on account of decreased energy use for mulch, fumigation and cultivations in addition to improved yields decreasing the N and P balance. The protected container crops, the coir grown table crops in particular, had the lowest sustainability profile per ha as a result of greater nutrient inputs that impacted energy use, GHG emissions and the nutrient balance. It did not improve for multiple crops on account of all inputs used on a per year as opposed to some used on a per crop lifetime basis as in the soil grown systems. Per tonne however the coir systems for the first crop were similar to protected and fumigated System 1 on mineral soil although no reduction in inputs during the second year meant a poorer performance for two crops relative to the soil grown system (Figure 2). The system that had the greatest performance per tonne overall was the system 4 (no crop first year), followed by the protected organic systems with FYM then the protected organic system without FYM. Of the integrated systems, the summer planted crops that obtained two maincrop yields had greater performance. The recycling of plastic improved the performance of the protected crops relative to those without protection (Figures 5 - 8)
The main impacts associated with the protection of crops with polytunnels are energy input, GHG emissions, water use, net margin and local employment. (Appendix Table 22). The factor by which the input or output increases or decreases (difference ratio) describes the magnitude of change. A value of 1 indicates no change, above 1 indicates an increase while below 1 a decrease (for example 2 indicates that inputs/outputs are doubled, 0.5 that they are halved). An improvement in yield between systems of greater than the difference ratio/ha indicates that per tonne, the improved yield system is more efficient. An impact on nitrate leaching, ecotoxicity and visual impact is also observed. The protection of a crop increases the energy input by 67 GJ/ha, GHG emissions by 2.46 eq tCO2/ha and water use by 750 and 160 m3/ha for soil and peat container systems respectively. For one crop, protection resulted in an improved margin of £13,949.00 and £18,621.00 for one and two crops respectively. There is also the likelihood of a premium for earlier produced crops. The increase in local employment associated with tunnel construction and maintenance may be up to 391 hours/ha although use of casual labour in a ratio of 3:1 means it is more likely to be in the region of 98 hrs/ha. The local employment associated with protected strawberry crops is estimated to increase by 98 hrs/ha, to 160 hrs/ha relative to 62 hrs/ha in non-protected crops. The risk of nitrate leaching may be reduced on account of both prevention of rainfall infiltration through the soil in the alleys during the spring and increased yields and thus N removal from beneath the mulch. Visual impact is increased, however the temporary nature of the structures mitigates this somewhat where it will be limited to the spring. Ecotoxicity is reduced by a score of 28 (14%) on account of reduced sprays for Botrytis, no application of Elvaron Multi and reduction in the risk of spray drift into the field margins. Per ha, the sustainability profile for the protected System 3 is lower than for the non-protected system 4, mainly attributed to increased energy input and GHG emissions (Figure 1). Yields improved in protected Junebearer first crops relative to non-protected crops from 6.4 t/ha (Sytem 4) to 18 t/ha (System 3), an increase by a factor of 2.8. Per ha, none of the criteria selected were greater than a factor of 2.2 (energy) for protected versus non-protected crops thus per tonne, the protected system performed more effectively than the non-protected system. Per tonne, the energy input for one crop is reduced in protected sytems by 2.1 GJ/t and GHG emissions by 0.12 eq tCO2. Nutrient loss and balances are also decreased, mainly on account of the increased removal of nutrients from the system. Net margin is improved by 770.00/t on account of the 3 fold improvement in yield. It must be emphasised however that only one example was available for each system. For two crops, the second year non-protected crops improved in yield relative to the protected crops to give a combined yield of 20 and 37 t/ha for protected and non-protected crops respectively, a ratio of 1.9. Per ha, for two crops, energy and GHG emissions were increased by a factor greater than 1.9 (Appendix Table 23) thus for two crops these two criteria are more efficient in non-protected systems. The other criteria remain more efficient in the protected system. Although the recycling of plastic decreases the ratio of energy input and GHG emissions relative to the non-protected crop, the yield improvements are not sufficient in the protected systems for two crops to render protected crops more energy or GHG emissions efficient per tonne of class 1 fruit although they remain more efficient for one crop (Appendix Tables 24 and 25).
The main impacts associated with crop fumigation are energy input, GHG emissions and ecotoxicity (Appendix Table 22). Fumigation with chloropicrin (System 2, fumigation non-protection) at 80 % full rate increases the energy input by 38.2 GJ/ha and GHG emissions by 2.21 eq tCO2 relative to System 4 (non-fumigated, non-protected). The cost is increased by up to £530.00 (400 l/ha) /ha and ecotoxicity by a score of 17 (9%). The impact on the other criteria is negligible although improved yields improve the nutrient uptake efficiency and reduce the balance. Yield improvements in fumigated non-protected Junebearer crops relative to non-fumigated non-protected crops from the grower interviews were on average 1.3 t/t for first crops and 1.2 t/t for second crops, an improved margin of A comparison on the same site with for example, a split plot assessment, would be required to quantify yield improvement accurately. The energy and GHG emissions of fumigated crops
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are increased by a greater ratio than the yield improvements (Appendix Table 22) and thus are less energy efficient and have greater GHG emissions per tonne of class 1 fruit for one crop. For two crops the energy input and GHG emissions per tonne of class 1 fruit remain slightly higher than the non-fumigated System 4 although the difference is reduced. This is on account of the fumigant inputs dispersed between two as opposed to one crop. Fumigation with chloropicrin contributes 17 points to the overall ecotoxicity score (9%) (Appendix Table 22). Crops may be summer planted as opposed to spring and obtain two maincrops. Inputs tend to be similar, with the exception of the crop protection for a maincrop as opposed to a 60-day programme. The energy input for a maincrop programme increases by 4.5 GJ/ha, the GWP by 0.23 eq tCO2/ha and the ecotoxicity by a score of 76. Soil erosion and N leaching risk are reduced, as are the N and P budgets while the economic output improves on account of improved yields. Similar trends are observed in the everbearer crops as the Junebearer.
Fumigation and protection combined (System 1) increase energy inputs by 105.1 GJ/ha, GHG emissions by 4.67 eq tCO2 and costs by £7,226.00 for first crops relative to non-fumigated non-protected system 4 (Appendix Table 22). The yield for one crop increased by a mean factor of 2.1 and 3.0 t/t on mineral and clay soils respectively. With respect to margin, System 1 on both soil types was greater than System 4. The variations in yield within System 1 resulted in those crops on clay soils being more energy efficient with fewer GHG emissions per tonne of class 1 fruit than System 4 (Appendix Figures 5 and 15) while the mean yield for those System 1 crops on other mineral soils resulted in a less energy efficient crop (Appendix Tables 24 and 25).
The impact of organic strawberry production systems (either with no nutrients applied or 40 t/ha FYM applied) are mainly nitrogen leaching, the nutrient balance, ecotoxicity and net margin (Appendix Table 22). To a lesser extent energy, GHG emissions, soil erosion and local employment are also impacted. Ecotoxicity scores for organic crops are 0 while nutrient recycling is 100% thus organic crops will always perform better on these two criteria than integrated crops irrespective of yield differences. In the organic crops that did not apply FYM the N loss from the alleys was similar to the integrated crops, while the risk beneath the mulch was reduced. A reduction in the nutrient balance to 9 and 18 kgN/ha and –0.6 and –1.1 kgP/ha for one and two crops respectively were observed, compared to 34.6 and 16.1 for N and P one crop for integrated systems. The nutrient balance was the lowest for all the systems considered while N leaching was also low in organic crops that did not apply FYM. The opposite was noted for these criteria in the organic crops to which 40 t/ha FYM was applied. The nutrient balance was the highest for all systems considered on account of the high overall nutrient content within the FYM. The N balance was 209.3 kgN/ha for one crop, 104.8 kgN/ha for two crops compared to 33.9 and 71.6 kgN/ha in the integrated systems. The P balance followed a similar trend, 59.5 kgP/ha for one crop, 57.6 kgP/ha for two crops compared to 16.0 and 31.9 kgN/ha in the integrated System 3. Nutrient use efficiency is greatest in the organic crop that utilises existing soil fertility although a compromise on reduced yields is required. For organic crops that apply FYM the N balance per crop is increased by a factor of 6.2 and 2.7relative to a integrated system for first and second crops while the P balance is 3.7 and 1.8 times as great as a integrated system. The organic crop to which FYM is applied increases in yield by factors of 0.94 and 1 relative to System 3 for one and two crops respectively although yield data for System 3 on clay soil was not available. Nutrient use efficiency per tonne of class 1 fruit is therefore greater in the integrated systems relative to the fertilised organic crop (Appendix Tables 24 and 25). The reduction of FYM to 25 t/ha reduced the N balance to 138.9 and 69.9 and the P balance to 36.7 and 34.7 kgP/ha (Appendix Tables 26 and 27). For N this is 4.1 and 1.0 times as great as for a integrated crop and for P 2.3 and 1.1 for one and two crops respectively. The nutrient balance in an organic crop to which 25 t/ha FYM is applied has a greater nutrient surplus during the first crop, however it will be reduced to similar levels as a integrated system during the second crop. The risk of leaching during the second year after application of the FYM remains high, 5.9 times as great. The impact on yield however requires quantification. For organic crops that do not apply FYM yields differ by a factor of 0.63 (11.5 t/ha compared to 18 t/ha) for one crop and 0.61 for two crops (23 t/ha compared to 37 t/ha) relative to the non-fumigated protected system 3. The nutrient balance per tonne of class 1 fruit is lower than for the integrated System 3 while N leaching is similar. The reduction in yield does result in increased energy input and GHG emissions per tonne by 3.6 GJ/t and 0.1 eq tCO2 respectively for one crop and 3.0 GJ/t and 0.1 eq tCO2 respectively for two crops (Appendix Tables 24 and 25). The net margin in both organic crops increases considerably relative to the integrated System 3 on account of the greater premium, £4,000.00/t for organic produce compared to £1750.00/t for integrated produce and the reduction in costs for crop protection products and fertiliser. The net margin increases by £20,000.00 and £38,000.00 /ha for one crop, and £39,000.00 and £85,000.00 for two crops for non-FYM and FYM applied crops respectively. The risk of soil erosion is lower for organic crops to which FYM is applied, 0.2 of the risk associated with the soil grown System 3, on account of the presence of organic matter in the alleys during the winter. Local employment is lower, 0.7 of the hours for System 3 on account of the reduction in spray operations. The impact on water use and visual impact relative to System 3 is negligible.
The main impact associated with peat container crops relative to non-fumigated soil crops are nitrate leaching, the nutrient balance, water use and net margin. The energy use was similar to the integrated System 3 for table crops although lower if placed on raised beds while GHG emissions increased slightly, by a factor of 1.1 (Appendix Table 22). No yield data was available for non-protected coir systems so the protected non-fumigated system 3 was used to compare the impact of container crops relative to soil grown systems. The nutrient balance was 2.7 and 2.6 times as great for N and 2.2 and 2.2 times as great for P in the peat container crops on tables for one (Appendix Table 22) and two crops (Appendix Table 23)on account of the greater quantity of N and P applied, although the application is to media that may be removed from the system completely unlike soil grown crops. Soil grown systems thus use N and P more efficiently. The risk of nitrate leaching was greater on raised
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beds on account of the greater area of fallow soil exposed to rainfall and the larger quantity of nutrients applied to the media that may be lost within drainage from the bag. Water use decreased in peat crops, a total of 0.7 of the quantity applied to the soil grown System 3. Net margin decreased per ha on account of the expenditure for media while yields remained similar. The yields are slightly higher for both one and two crops in peat container systems thus per tonne of class 1 fruit, water use efficiency is greater in protected peat Junebearer systems relative to soil grown protected crops (Appendix Table 24).
The main impacts associated with coir container crops are GHG emissions, nitrate leaching in raised beds, the nutrient balance and water use. Yield in Junebearer coir systems was similar to the soil grown system 3 for one crop but increased by a factor of 1.1 for two crops. The energy input was similar to the soil grown system 3 for one crop on raised beds but increased by a factor of 1.1 in table crops (Appendix Table 22). GHG emissions increased by 1.4 for one crop. For two crops energy use increased by 1.3 and GHG by 1.6 on tables and (Appendix Table 23). Energy use per tonne is similar to the soil grown system 3 for one crop (Appendix Table 24) on raised beds although slightly higher on tables, for two crops on tables both energy use and GHG emissions are higher relative to the soil grown system 3. The nutrient balance per ha in coir crops was 4.9 and 4.6 times as great for N and 2.3 and 2.5 times as great for P relative to the soil grown System 3 for one and two crops on account of the greater quantity of N and P applied. Soil grown systems thus use N and P more efficiently than container crops although peat requires less nutrient input than coir. Water use decreased slightly in coir crops, 0.96 of the quantity applied to soil grown crops. The yields are similar or slightly higher thus water use efficiency is slightly greater in coir Junebearer systems relative to soil grown protected crops. Soil erosion risk is greatest in table crops for both peat and coir systems, a factor of 1.5, on account of the limited ground cover. No examples for soil grown non-fumigated everbearer crops were obtained, however the yields for everbearer protected coir systems relative to soil grown fumigated protected systems showed a similar trend to Junebearer crops. The impacts therefore were also similar.
3.12. Weighted sustainability profiles The greatest weighting was given to energy and GHG emissions, followed by net margin. Nutrient, pesticide
and water use impacted at the regional scale while nutrient recycling, soil erosion, local employment and visual impact at the local scale. Those crops that performed greatest on the former three criteria had the largest overall weighted sustainability profile (Figures 9 - 12). Those systems that performed better on the smaller scale weightings such as soil erosion, local employment and visual impact had a lower weighted sustainability profile. The recycling of plastic had reductions in energy use and GWP and thus improved the weighted performance of the protected crops (Figures 13 - 16).
3.13. Comparison with Spanish productionIn Spain there are two systems of strawberry production. The main system is similar to first year fumigated
protected Junebearer crops within the UK since all materials are replaced and beds re-formed each year. The plants in Spain are chilled, the quantity of which can be manipulated so that the plants remain small and crop over a long period (D. Simpson, pers comm). As a result the planting densities are 2 to 3 times greater than in the UK with greater associated yields per hectare. The water requirement per plant per day is lower than in the UK on account of the smaller size of the plants although the water requirement per hectare tends to be higher because of the high planting density and the sandy soil. This is applicable to the application of nutrients within the irrigation water also. Mature plants of Elsanta or Florence grown in the UK produce a very similar yield per plant to Camarosa in Spain but the harvesting is concentrated into a period of 3 - 4 weeks. The Huelva region has sandy soil thus crops require increased N fertiliser and irrigation water and as a result, there may also be an increased risk of N leaching from beneath the beds. Energy use per crop/ha for culture and crop protection is likely to be similar to the fumigated protected System 1 for one crop, however the energy for fertiliser inputs will be greater. Yields are greater however, thus per tonne, energy use and GHG emissions are reduced. The crops are not strawed on account of less weed growth associated with the less fertile sandy soils however the site topography is mostly flat (0% slope) thus soil erosion risk minimal. The increased transport distance of 2165 km (Huelva to Dover) have an associated increased energy input of 2.66 GJ/ tonne class 1 fruit assuming transport with a refrigerated tuck at 0.031 l/t/km (Kinnon and McGregor, 1998). If the return journey is empty an additional 2165 km without refrigeration will be required, a further 1.37 GJ/t.
4.0. Discussion4.1. Energy
Previous energy balance studies have focused on arable crop production and found that the greatest contributor to energy input to be from the manufacture costs associated with mineral nitrogen fertiliser production (Tzilivakis et al., 2004). For the UK strawberry crop that has a relatively low nitrogen requirement, the greatest energy inputs were associated with the manufacture of soil fumigants and with the plastic used for polytunnels and mulch. The overall energy input for strawberry production in the UK ranged between 15.8 to 168.3 GJ/ha. Energy efficiency per crop/ha for soil grown systems and container systems on raised beds may be improved with the growing of a second or greater still with a third crop assuming yields are maintained. The recycling of plastics offers potential to reduce the energy input per crop significantly for most systems, particularly in protected crops. The system with the greatest energy efficiency per tonne of class 1 yield did not use fumigation, protection, polyethylene mulch or irrigation. In general, for Junebearer crops, the improved yields associated with the
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protection of first year crops results in a similar or lower energy input per tonne of class 1 fruit than non-protected first year crops, particularly if the plastic is recycled. However, for those crops grown for a second year, yield increases for the non-protected systems result in a decrease in the energy per tonne of class 1 fruit relative to the protected systems such that energy efficiency is greater. It is particularly evident in the summer planted non-protected system 2 that has two maincrop yields and thus a greater energy efficiency for both first and second crops. It should be noted that the considerable variation in yields in some systems, the protected fumigated soil grown Junebearer crops in particular, requires interpretation of the system efficiency with caution. For everbearer crops the energy efficiency was greatest in the non-protected systems for both years. The difference in yields for the everbear crops was not as pronounced as for the Junebearer systems. Many of the calculations and results in this study rely upon the yield data from a small number of samples that may have one example per system or where possible, the mean yield values are used.
Crop protection was dictated by whether 60 day or maincrop June bearer or everbearer and whether protection was used. Most methods of crop protection required the use of synthetic pesticides, with the exception of Majestik® used on the organic crops, the use of Phytoselius to control spider mite, B. thuringiensis for lepidopteran larvae and sulphur against mildew. Straw mulch and inter row cultuivation were used as methods of weed suppression in addition to herbicides by some growers. The energy input for crop protection in strawberry production was found to be largely influenced by the use of soil fumigation. The energy for the manufacture per kg of active ingredient for soil fumigants is smaller than most other pesticides, 66.8 MJ/kg for a halogenated hydrocarbon such as methyl bromide or chloropicrin (Pimentel, 1980) and 80 MJ/kg for dithiocarbamate fumigants such as metam sodium (Green, 1987). This is compared to an average of 240.5 MJ/kg for all pesticide active ingredients (Green, 1987). Soil fumigants are however, applied at greater quantities than many other crop protection products and contain a greater proportion of active ingredient, between 94 and 100% for most. Most growers stated that they fumigated with either chloropicrin or methyl bromide. Chloropicrin is applied at between 200 and 400 l/ha (Dewco-Lloyd Ltd pers comm), an energy requirement of 21.9 – 43.9 GJ/ha to manufacture with an additional energy input for its application. Many of the growers interviewed test the soil for Verticillium and target fumigation applications accordingly and this has important implications for reducing the energy inputs associated with crop protection. The energy balance and GWP for fumigaton in the current study accounted for a 20 % reduction from the targeting of applications and was based on 80% of the full application rate although reductions may be greater. The herbicide applications had the greatest energy requirement of the other crop protection applications although the use of straw mulch eliminated the need for an application during April. Straw is a by-product of the previous wheat crop so no energy value was assigned for its production although an energy cost was assumed for its transport from the field to a storage area and then to the strawberry crop. The manufacture energy for products to control Botrytis such as Elvaron Multi tend to be greater than for mildew and insecticide treatments, with a range of 57 – 328 MJ/ha. The use of protection reduced the number of Botrytis treatments and eliminated Elvaron Multi, that is applied in greater doses (3.4 kg/ha) than other treatments, from the programme. The energy input is reduced by 328 MJ per application for manufacture with an additional reduction of 27 MJ/ha for spraying.
Fertiliser inputs were dictated by soil type and type of growing media and whether June bearer or everbearer. The energy required for the manufacture of fertiliser applied to soil grown crops assuming MAFF (2000) recommendations is relatively low, in particular nitrogen, compared to most other crops since strawberry crops do not require large inputs of fertiliser. The nutrient regimes provided by the growers however were variable with excessive quantities of nitrogen fertiliser applied to soil grown crops in certain cases. The energy input for nitrogen fertiliser manufacture and associated GHG emissions from nitrate fertiliser in particular is high thus application of minimal quantities important. The greatest quantities of nitrogen fertiliser were applied to container grown crops, those with coir substrate in particular that had 177 kgN/ha and 224 kgN/ha for Junebearer and everbearer crops respectively compared to soil grown crops that required between 40 – 50 kg N/ha. The application of 40 t/ha of livestock manure in the organic systems comprised a significant portion of the energy input it is therefore important to minimise the haulage distance. Soil grown crops tend to apply nutrients through the irrigation system therefore additional energy for application is not required. The large volume of FYM requires a total of 5.7 GJ including transport, application and indirect energy. Recommendations to apply 25 t/ha by Lampkin (2004) offer the potential to reduce the energy input for application and haulage further, to 3.9 GJ/ha. It is assumed that the manure was transported 10 km and minimising this distance is an important consideration. It is also worth noting that the industrial processes to manufacture fertiliser are becoming more energy efficient and as a consequence, the energy input for the manufacture of ammonium nitrate and phosphorous fertiliser will decrease in the future (Jenssen & Kongshaug, 2003). Mineral fertiliser therefore, will probably become a more energy efficient method to feed crops compared to farmyard manure unless the manure is produced near to the field where it is applied. The nutrient balance in organic crops is part of a rotation and fertility building crops were not included in the study so the energy input for organic crops may be an underestimate.
The energy input for cultivation is driven by soil type or the use of tables, in which case it is not used. The energy use increases, particularly for the deep subsoiling operations, on heavier clay soils relative to sandy clay loam or sand. Cultivations for bed preparation last the lifetime of the crop thus growing a second or third crop will reduce inputs by 50% and 66% per crop respectively. The reductions will be greatest on clay soils. All growers interviewed that grew container crops on the ground used raised beds upon which the bags were placed. Since the crop is contained within the medium within the bag, it may be possible to use minimum tillage for ground preparation. Bailey et al. (2003) in a comparison of integrated and integrated production concluded that the use
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of minimum tillage in integrated systems to be one of the key differences between the energy inputs of the two. In strawberry crops however beds provide drainage from the bag and the raised position helps fruit presentation and picking thus it is not really a viable option. Subsoiling may be considered a whole-rotation improvement and although some of the smaller growers did not rotate, the larger producers tended to use a rotation. The energy for subsoiling therefore should also be associated with other crops in the rotation. The materials used by growers for tables tend to be scrap material thus the energy input for the manufacture is considerably lower than new material. The variability in material used, its volume and the lifespan of the material however meant a precise estimate of the energy input for the manufacture of tables is difficult to quantify. Generally, energy use per crop will be greater than for bed preparation on account of the large volume of materials used.
Many growers utilise sources such as boreholes and reservoirs and thus ‘grey water’, that is, water that has not been treated for mains supply, estimated to require 2.95 MJ/ m3 treated (Wessex Water LTD). Water usage was typically around 2500 m3/ha/year for protected crops that would have required an additional 7.4 GJ/ha/year if extracted from mains supplies.
4.2. GWPThe GHG emissions in strawberry crops vary between systems both on a per ha and per tonne of class 1
fruit basis. Coir grown crops in both the Junebearer and everbearer systems had the greatest GHG emissions per ha, mainly as a result of the greater quantities of nitrate fertiliser applied since coir tends to buffer N preventing its availability to the plant. The GWP per MJ input is greater in nitrogen fertilisers, particularly ammonium and potassium nitrate since the manufacture of nitric acid releases large quantities of N2O (Jenssen and Konshaug, 2003), that has a GWP factor of 296 (Ramaswamy, 2001, cited Houghton et al., 2003). The greater yields within coir systems however results in a fewer GHG emissions per tonne than some of the soil grown systems however per crop for two crops, the GHG emissions per tonne are higher than the soil grown systems in which GHG emissions are reduced per ha with multiple crops. As for energy use per tonne, the system with the fewest GHG emissions was the higher yielding summer planted non-protected system 2 or the non-protected non-fumigated system 4 (no crop first year) that minimised inputs while maintaining good yields. The less pronounced reduction in GHG emissions per tonne for recycled plastics, 0.02 eq tCO2/t class 1 fruit, relative to energy input is a result of much of the carbon remaining within the plastic polymer chain while in a landfill site. If the plastic was to be disposed of by burning and the carbon liberated immediately the impact of recycling on GHG emissions would be greater within the 100 year timescale considered emissions associated with its disposal are shared between several products.
De-nitrification within strawberry crops is low, although it tends to be greater on soils prone to waterlogging, such as the clay soils within the alleys in strawberry crops. The loss of N to denitrification beneath mulch has been regarded as negligible in previous studies including strawberry crops to which excessive irrigation was applied (Guimera et al., 2002) although they were grown on sand soils that drain more freely. Rainfall is unable to infiltrate the soil beneath the mulch while the water applied beneath the mulch is controlled and limited to the summer when the crop is actively growing. The water-logging of soils beneath the mulch during autumn and spring is therefore dependent upon the quantity of irrigation water applied but is unlikely to occur for those growers that use moisture sensors and irrigate for shorter daily periods. A reduction in de-nitrification in integrated soil grown systems would be difficult to achieve. De-nitrification was greater in the organic systems on account of the FYM applied to the alleys that are exposed to rainfall and water logging. The reduction in the quantity applied may reduce de-nitrification and the associated GHG emissions however impact on yields must also be considered. The de-nitrification in container crops is again unlikely since they are free draining and water-logging of the media unlikley.
4.3. Nitrate leachingThe N applied to soil grown strawberry crops relative to other crops is low thus the risk of N leaching
greatly reduced. The presence of water impermeable barriers is likely to reduce the risk further. Two environments exist at ground level within most strawberry crop systems. Firstly, a protected area that is either not vulnerable to rainfall infiltration or reduced infiltration depending upon the material and secondly, a zone that is not covered with ground vegetation and that is exposed to rainfall although straw mulch may be present or natural regeneration of vegetation allowed. Goulding et al (2000) commented that arable crops produced under the most environmentally conscious methods would reduce nitrate leaching to 20 kgN/ha/yr. Most of the strawberry production systems were estimated to have leaching figures similar to this value or below. The N applied as fertiliser is at greatest risk to loss from leaching if heavy rainfall occurs within 3-4 weeks of application however in strawberry crops, the N is applied beneath a water impermeable mulch and the exposed soil within the crop does not receive N, with the exception of the FYM applied to some organic crops and the System 4 (no crop first year) that does not use a mulch. Although rainfall has been found to penetrate mulch through the planting holes, generally there is little water accumulated under plastic mulch after planting (Hanada, 1991). Further studies have supported this observation by concluding that Virtually Impermeable Film (VIF), semi-permeable bio-degradable mulch or straw would either prevent or reduce the impact of rainfall water from penetrating and infiltrating the seedbed beneath (Lamont, 1993; Locascio et al., 1985; Romic et al., 2003; Sur et al., 1991). The loss of nitrogen to leaching is either prevented or reduced (Lamont, 1993; Locascio et al., 1985) and nutrient retention within the crop root zone increased that allows more efficient nutrient use by the crop (Cannington et al., 1975). In a study of the impact of mulches in bell pepper (Capsicum annum L.) cultivation, Romic et al (2003)
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found that black plastic mulches remained impermeable to water throughout the season. As a consequence the average N leached was reduced by between 62.3% and 43.3% during a season of high (768.1 mm) and low (496 mm) rainfall respectively. Loss beneath the mulch may occur if excess nutrients are applied in quantities greater than the crop will utilise or if irrigation is applied such that the soil is wetted beyond field capacity and water is able to percolate through the soil profile. The over-irrigation of crops may increase summer drainage and the risk of nitrate leaching during the summer (Hess, 1999) while excessive N application to strawberry crops by fertigation may cause groundwater pollution as a result of leaching (Guimerà et al., 1995). The N balance beneath the mulch for UK strawberry crops would suggest that in most soil grown crops most N applied is assimilated and either removed with the fruit or re-distributed within the alleys after mowing. Some crops however do not appear to yield sufficiently highly to remove the N applied beneath the mulch and this excess of nutrients may pose a risk. Generally, this is likely to be low, less than 10 kgN/ha, on account of the small quantities of N applied initially. Those growers that irrigate for longer daily periods and maintain the water levels closer to field capacity increase the risk of leaching beneath the mulch. Although the application rates of mineral N varied between growers the average application rates for soil grown Junebearer and everbearer crops were similar to the MAFF (2000) recommendations. Relative to other crops, the recommendations for strawberry are relatively small, between 40 and 60 kgN/ha for Junebearer and 50 kgN/ha for everbearer crops for a Soil Nitrogen Supply index of 1. For a mineral soil of SNS index 1 winter wheat requires 220 kgN/ha, oilseed rape 190 kgN/ha and brussels sprouts 300 kgN/ha. The quantity of N at risk to loss is therefore lower and since it is applied during the summer in several applications beneath a water impermeable mulch, it is not subject to loss from heavy rainfall occurring immediately after application. The run-off from container crops may present a risk on account of the greater quantity of N applied, in particular to coir crops. The N leached from container crops is dependent upon the type of growing media, the method of N application and the quantity of irrigation water applied (Bunt, 1988; Wright and Niemiera, 1987). Many growers use bags for container crops that are enclosed at the top thus performing a similar function to the mulch with respect to the prevention of the infiltration of rainwater. The leaching patterns for bags placed on raised beds are similar to soil grown crops although a greater area of fallow soil may be exposed directly to rainfall and the risk of leaching. Those container crops that are grown on tables are likely to have an area of soil beneath them that may not have been tilled for many years that will be at a lower risk to N leaching than those placed on recently tilled beds. Some container crops may be grown in trays or pots that are open at the top and allow the infiltration of rainwater into the growing media and therefore be exposed to nutrient loss. This may be a particular risk during the winter months (Colangelo and Brand, 2001) however many container grown crops in the grower interviews were not grown for more than 1 year thus the risk is removed. Most growers deliver nutrients to the container crops via fertigation as opposed to the incorporation of control release fertiliser into the growing media. The method of fertiliser application to container crops may effect N loss, with greater losses observed from soil incorporated fertiliser compared to the application from a top dressing or fertigation. It was attributed to the intermittent drying of the upper growing medium layers between irrigations, once per week in this case. Nutrients applied through fertigation to the upper layers of the medium moved down through the soil profile before they were leached from the container. Consequently there is a greater probability that the nutrient will come in to contact with the root system during this time compared to if incorporated within the medium. Peat substrates have a greater total water holding capacity and more readily available water content than coconut coir fibre in addition to lower air filled porosity for similar particle size distribution (Noguera et al., 2000). This was reflected in the smaller quantities of irrigation water applied to peat container crops. The water percolating through the media and into the soil beneath the bags may be reduced in peat growing media. Container crops offer the potential to maintain the media within which the crop roots are contained at field capacity while the soil beneath the bag remains drier and as a consequence, N contained within run-off from the bags will remain within the soil initially. The coir systems required the greatest N inputs. Coir fibre has a high carbon/nitrogen ratio, between 75 and 97 in Sri-Lankan coir (Abad et al., 2002). Nitrogen immobilisation occurs in media with a C/N ratio above 25 (Wallace et al., 2004) consequently additional N is required in coir systems to allow sufficient quantities to be available to the strawberry plants. The quantity of N applied to peat media was also lower relative to coir substrate potentially reducing the risk further. Table grown crops may be able to trap runoff from bags and prevent all N loss to the soil beneath.
The second environment within the field is the uncropped area of soil between the plastic covered rows and it is likely that N will be lost from most systems in this area where in most integrated crops, the soil is maintained weed free. The current study assumed leaching patterns from this area to be similar to that of fallow land. Losses from the fallow area of a strawberry crop will be highly dependent upon the management of the previous crop. Nitrogen losses following cereal crops tends to be during the winter from the nitrate formed by the mineralisation of organic matter in the soil during the period when N uptake by the crop does not occur (Stopes et al., 2002). This accounts for some of the N leached from a first year strawberry crop, particularly spring planted crops where the entire seedbed is fallow during the winter before application of a mulch. The non-tillage of second or third crops will probably reduce the risk of leaching further on account of less mineralisation of soil organic matter. Losses of 10 kgN/ha/yr were found during winter wheat crops to which no fertiliser N was applied (Goulding, 2000). Strawberry production in the UK typically uses a straw mulch. The presence of straw mulch during the winter was found to reduce the leaching of nitrate from the interrow area in strawberry crops (Neuweiler et al., 2003). The mineral nitrogen content was also found to decrease under straw mulch during the late summer, attributed to N fixation caused by its decomposition (Jawson and Elliott, 1986). The presence of straw mulch is therefore likely to reduce N loss during strawberry production, particularly between rows for second or third
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strawberry crops. Those organic crops that allowed natural regeneration of arable weed species also may reduce the risk of N leaching although this will be dependent upon the quantity of weed establishment. Partial and complete covering of an uncroppped weed free seedbed was found to reduce nitrogen loss from surface run-off by 67.8% and 83.3% for 3 t/ha and 6 t/ha of straw applied respectively and allow a greater volume to pass instead through the soil profile (Sur et al., 1991). The UK strawberry growers typically apply up to 18 t/ha of straw to the alleys thus it is likely that N loss from surface run-off low. The risk of soil loss is discussed further in section 4.6. Leaching losses were greatest in the organic crops to which 40 t/ha FYM was applied to the fallow alleys in addition to the beds. Previous studies have found that fallow land may be vulnerable to large leaching losses, particularly if organic manure is applied during the winter. A loss of 188 kgN/ha was recorded from fallow land to which 230 kgN/ha as FYM was applied during mid December in the west of England (Allingham et al., 2002). Losses are likely to be greatest if applied during the autumn or winter but will be reduced when applied during the spring or summer (Allingham et al., 2002) as was the case for spring and summer planted organic strawberry crops. The application of 40 t/ha pre planting to organic summer planted Junebearer crops poses the greatest risk to nitrate loss in UK strawberry production, particularly during the second crop. The natural regeneration of vegetation within the alleys may remove some N however the establishment of cover may be variable. The application of 25 t/ha reduces N leaching in such systems however if it were possible to target application to the beds alone while not likely to be practical leaching, denitrification the N surplus post harvest would be reduced further. The spring applied FYM to organic everbearer crops had a lower N leaching risk than that applied during the summer since the first year included the period before FYM application (25th July – 15th March) wheras the summer applied FYM was present for the entire period. Losses to leaching in the second year of the spring sown everbearer crop is likely to increase relative to the first crop when the fallow soil with incorporated FYM is exposed to increased rainfall during the winter.
Although leaching from the strawberry crop itself would appear low, the impact on the soil mineral N levels and the risk of leaching in following crops requires consideration. The leaching of nitrate under plastic mulch may be reduced however as a result mineral N will accumulate in the soil underneath. Latet et al (2002) in a field of strawberry crops found greater quantities of mineral N present in the soil under black polyethylene mulch compared to that on open ground for both N applied pre-planting during the summer and N applied during the spring. This was attributed to greater rates of N mineralisation and reduced N leaching under the mulch. The presence of N under mulch increased further with the use of fertigation. If mineral N has accumulated in the upper soil profile beneath the mulch (Hanada, 1991; Latet et al., 2002) then upon removal of the mulch the increased mineral N is at risk to leaching. It has also been found that fallow soil is at greater risk to N leaching upon ploughing out (Froment et al., 1999) and this has implications for the bare soil between rows. The nitrate leaching potential of soil as soil mineral nitrogen (SMN) for one year rotational set-aside was found to be greatest after uncultivated fallow that had been kept weed free. (Froment et al., 1999). The SMN was greatest in the fallow treatment as a result of the mineralisation of N from organic matter within the topsoil after cultivation. This represented an increase in SMN compared to continuous cereal cropping and a potential increased risk of nitrate leaching during the winter after the ploughing out of the set-aside land during the autumn. An uncultivated soil left to natural regeneration with less potential for N mineralisation could reduce leaching (Webster and Goulding, 1995) although the potential for N leaching may increase in the short term if the natural regeneration is sparse or if a sown cover did not establish. This could be applicable to the organic systems that apply FYM and allow natural regeneration. Clotuche et al (1998) also found soil nitrate levels to be high in set-aside land that had undergone natural regeneration on account of the variability in established cover and nitrogen uptake by the species present. For 3-year and 5-year rotational set-aside SMN and potential nitrate leaching losses increased during the winter after ploughing out of perennial ryegrass and natural regeneration compared to continuous arable cropping (Chalmers et al., 2001). The likely surplus N after crop removal and N available for leaching in subsequent crops was estimated with an N balance.
4.4. Nutrient balanceThe nutrient balance examines the relationship between nutrients applied, namely from fertiliser, and those
removed with the fruit that increases with yield and provides a measure of use efficiency. For soil grown crops, nutrient application rates are determined by the SNS index and are independent of system. No relationship between predicted yield and the N and P applied by the growers that stated their application rates was found, many growers used a recipe to maintain constant nutrient concentrations within the irrigation water. Those soil grown systems that use measures such as protection or fumigation that improve yields are more likely to improve nutrient uptake/ha and use efficiency. The number of examples for peat and coir systems was insufficient to assess. The N balance takes account of the N remaining within the soil after the crop is grubbed into the soil and potential risk to N loss for following crops. It measures N use efficiency but also accounts for inputs and outputs other than from fertiliser N and in the fruit. Although leaching affects the balance and is accounted for in the previous section, inclusion within the overall balance highlights systems that may not lose large quantities of N to leaching (for example, as a result of the presence of water impermeable covers) but do not remove it within the fruit either and result in a large N surplus after removal of the crop. The N surplus in soil grown integrated crops was generally low, between 27.1 and 41.5 kgN/ha and comparable to cereal crops (Berry et al, 2003). Strawberries are a low N demanding crop compared to other crops and most growers state the use of soil and leaf analysis to optimise inputs. For soil grown integrated crops therefore assuming analyses are used there is probably little room for a reduction in inputs. A small number of growers appear to use excessive quantities of N
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for soil grown crops which for a crop that does not utilise large quantities, will potentially leave a greater surplus after removal. The shallow root system in strawberry plants is likely to increase the risk of N accumulation in the lower soil profile, particularly for crops grown for two or three years. The application of 40 t/ha FYM to organic crops caused a large N and P surplus to be present although the N surplus per crop is greatly reduced during the second year since N is obtained solely from the base dressing applied pre-planting. The application of 25 t/ha as opposed to 40 t/ha FYM reduces both the N surplus although in comparison to integrated crops it remains high. It may be advisable for organic crops to ensure that a winter sown crop follows the removal of the strawberry crop so that some N is removed before the winter. Most N uptake by the following crop will occur during the spring, almost three years after application of the original FYM base dressing thus much of the N contained within the FYM will be available. Where livestock manure is used, much of the crop’s nutrient requirements are supplied which recycles nutrients and improves the overall sustainability of the system. The container crops apply greater quantities of N and also incur a higher N surplus and a lower nutrient use efficiency per tonne of class 1 fruit. The nutrient balance in coir systems indicates a surplus of N post harvest, however the N remains immobilised until the fibre breaks down. It may also be applied elsewhere on the farm or completely removed from the system consequently the risk of N loss in following crops is likely to be low.
The P requirement for soil grown crops is determined by the soil concentration and then monitored with a leaf analysis and may be adjusted based on the expected yield and this will be influenced by the system. Only small quantities of P are removed with the fruit, 0.13 kg/t equivalent to 1.0 – 5.2 kgP per crop however the P accumulated by the crop during growth may be as much as 11.1 kgP/ha in the soil grown crops considered. The quantity of P applied by the growers was in most cases below the recommended quantity for a soil index of 2, in the region of 10 kgP/ha, although a small number applied in excess of the amount required for soil index 0. The P surplus was in the region of 9 kgP/ha for most soil grown crops. Although sandy soil may be prone to P depletion (Younie and Baars, 1997) a non sand soil has been shown to have an annual deficit of 2-4 kgP/ha for a period of 10 years without experience of a decline (Kaffka & Koepf, 1989). In general therefore, the levels of P are not depleted by soil grown strawberry crops and large surpluses do not occur in integrated crops. The greatest surplus was present in the organic crops to which 40 t/ha FYM was applied, mainly as a source of potassium in which a P surplus of between 56 and 60 kgP/ha for two crops resulted. The proportion of nutrients within organic manure may not be controlled as accurately as those delivered by fertigation. Phosphorous tends to be most prone to loss from surface run-off (Berry et al., 2003) and could be at risk in the organic crops to which 40 t/ha of FYM was applied, mainly as a source of potassium, to the fallow alleys between beds. The soil loss equation (Renard et al., 1997) suggests that the large volume of organic matter in FYM reduces the risk of surface run-off thus the risk of loss of P is also likely to be reduced. The P applied to container crops was greater than soil grown systems. The excess P may remain within the media thus the rate of application of any surplus onto the soil may be controlled by the grower after removal of the crop. Between 11% and 28% of the applied PO4-P (4.4 and 11.3 kgP/ha) to container crops was estimated lost to leaching (Broschat, 1995) but as with N, this will be intercepted by the soil beneath beds or has the potential to be removed from the system in table grown crops. The presence of straw reduces the risk of surface run-off (Renard et al., 1997) thus loss of excess P are also reduced.
4.5. Water use. In relation to crops such as sugar beet, the water requirement of strawberries is greater, 1546 – 2299
m3/ha compared to 500 m3/ha however it is delivered with more efficiency. The water is applied directly to the roots beneath an impermeable plastic mulch using trickle irrigation in most systems which does not allow significant losses to evaporation to occur compared to, for example, a high pressure boom sprayer.
Irrigation water is applied however in response to the maintenance of a percent of soil field capacity as opposed to individual plant requirements (D. Simpson, pers comm). Strawberry plants have a shallow rooting depth of about 25 cm, although this may be less on heavier soils where the roots spread horizontally as opposed to downward, and consequently a risk of movement of excess irrigation water and nutrients not removed by the crop within it below the root zone exists. The improvement of irrigation strategies to account for plant demand offers potential to reduce water use and the risk of leaching beneath the mulch in soil grown crops. Peat container crops applied less irrigation water than soil grown crops since peat soil has a greater water holding capacity than clay or other ‘mineral soils’. In areas where water shortages are an issue, peat container crops may be a more suitable option.
4.6. Pesticide ecotoxicityMuch of the habitat on and around most strawberry crops consisted of single species windbreaks of poplar or
Spanish alder, with little or no ground vegetation beneath. For the larger scale growers, the sensitive habitats such as ponds and woodland were limited to the edges of, or adjacent to, the growers land and thus were not directly bordering strawberry crops each year. Species for which Biodiversity Action Plans (BAPS) have been prepared that may be present within strawberry growing areas include Skylark (Alauda arvensis), Grey partridge (Perdix perdix) and Brown hare (Lepus europaeus). The Great crested newt (Triturus cristatus) may be present in adjacent water bodies during the breeding season or within field margins at other times of the year. Relevant Local Biodiversity Action Plans Priority Habitats of Regional Significance include Ancient and Species Rich Hedgerows. Strawberry production tends to occur in relatively small plot sizes of up to 4-5 ha. If grown in rotation with other crops such as wheat or grass, a mosaic of habitats within a small area will exist and may be of
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benefit to species such as the hare. The windbreaks are cut on a rotational basis thus a diversity in vertical structure of potential benefit to birds are maintained within production areas.
For integrated crops, the average ecotoxicity score for strawberry crops was 207, although this represented a worst case scenario and will be lower during years of lower pest and disease incidence. This average ecotoxicity score is higher than crops such as winter wheat and sugar beet, but lower than potatoes. Pesticide sprays are spatially targeted onto individual strawberry plants and from a lower height than a typical arable crop which reduces the risk of spray drift into non crop areas. This has important implications for listed Priority Habitats such as the Ancient and Species Rich Hedgerows. The plastic mulch is likely to intercept most pesticide that is not trapped by the crop within the beds and prevent its exposure to soil dwelling fauna while the presence of straw mulch reduces the impact of spray drift within the alleys. Further, the polytunnels also act to reduce drift into the field margins of any applications that are made to protected crops during the spring or autumn for Junebearer crops and everbearer crops respectively. The timing of the presence of tunnels may vary between individual growers and between years depending upon weather conditions thus the impact of protection on ecotoxicity scores may also vary. Protection reduces the number of sprays for Botrytis thus decreases the overall ecotoxicity score for integrated systems. They are essential for organic crops that do not have the option to use such products and are not grown commercially without protection in the UK on account of poor yields. The organic crops did not carry an associated risk from the application of crop protection products such as sulphur and Majestik®. In integrated crops that were fumigated the ecotoxicity score was greater on account of increased risk to soil dwelling fauna although its application beneath the plastic mulch meant the risk to fauna in field margins was negligible. The cumulative ecotoxicity scores from the other crop protection products meant it contributed 9% of the overall score for non-protected crops. Compared to other crops, for example sugar beet, that has an overall ecotoxicity score as low as 26, the contribution by fumigation with chloropicrin would be relatively high, 65%.
Agro-chemicals applied to container crops, in particular those applied as a drench such as chlorpyrifos, tend to be intercepted by the media, especially in peat that has a high organic matter content (Drakes et al., 2001). The disposal of growing media onto agricultural land has potential to cause environmental contamination if concentrated into a relatively small area and situated near a sensitive habitat feature such as a water body present all year. This risk is considered to be minimal if applied over a large area where dilution will occur and much of the chemical will be degraded within the topsoil (Drakes et al., 2001).
4.7. Soil erosionThe risk of soil erosion is increased by the gradient of the slope, the percentage area of the soil that is
exposed, the height that the water droplet falls and the size of the droplet (Wischmeier and Smith, 1978, Renard et al., 1997). Erosion within strawberry crops is predicted to be low on low to moderate slopes, mainly as a result of the cover on the soil surface provided either by the polyethylene mulch on the beds or straw within the alleys. However, the run-off from the plastic mulch before the application of straw mulch in, for example, summer planted crops is an important consideration, particularly on steeper gradients. The increased run-off from drainage from polytunnels may pose the greatest risk although this may only be to a limited number of alleys on account of most being under the cover of the tunnel. The water flow and droplet size is greater however the presence of straw within the alleys for most crops when tunnels are present reduces the impact of water striking the soil surface (Wischmeier and Smith, 1978, Renard et al., 1997). Erosion may be a problem in protected crops where tunnels are erected before the application of straw mulch to the alleys, and this will be increased with increased gradient of the slope. The organic crops did not use straw mulch within the alleys however the large volume of incorporated organic matter has similar erosion mitigating properties. Tillage operations tend to break aggregate bonds that increase the risk of erosion (Renard et al., 1997) thus non tillage for second and third crops or table crops also reduces the erosion risk.
4.8. Net marginAn economic return on strawberry crops, unlike arable crops, will in all probability require two or three years
after initial investment in materials is made. Many Junebearer crops have a negative margin during the first year on account of the high establishment costs but the margins increase for all crops taken on to a second year, particularly in soil grown crops. Margins were in general greatest as follows: organic soil grown systems > protected and fumigated soil > protected soil > protected peat container > fumigated soil > other. The organic crops command a higher price per tonne with fewer inputs so despite low yields in those that did not supplement soil nutrients with FYM, margins remained high. The use of protection improved margins in most cases and it is notable that the non-protected System 2 and System 4 had the greatest negative margin for one crop although the variable yields of the protected System 1 on mineral soil had a similar loss. Some early production systems, for example System 1 with fumigation and protection had a large variation in yield and this may be attributed to low yielding early crops during late April or May that achieve a premium when sold. The average price for class 1 fruit, taken from ABC (2004), does not account for the timing and associated premiums of produce sales thus the margins in protected Junebearer systems may be greater. Yields were also improved in those integrated soil grown systems that were fumigated. Container crops have a smaller improvement for two crops, mostly associated with tunnel erection costs distributed between more than one crop. For those crops taken on to a second year, the yields were the same with the exception of the coir system wheras increased yields for two crops were noted for all the soil grown systems. System 8 had considerable variation in yield and the mean
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margin for the system was negative for two crops on account of very low yields during both years for one grower. Of the integrated crops, the crops with the minimal inputs that maintained greater yields, namely the summer planted fumigated non-protected system 2 had the greatest margin of the integrated crops. Greater margins were also calculated for the summer planted protected crops also as a result of obtaining a maincrop yield during the first growing season.
The everbearer crops produced higher yields during the first year and as for Junebearer crops, the organic systems had the greatest margin. Again there was variation in yield between protected fumigated crops grown on ‘other mineral’ or clay soils with higher yields and thus margin on the clay soil. Most of the everbearer systems involved protection so comparisons of yield and thus margin improvement not possible. The margin of the non-protected fumigated System 11 was actually greater than the mean protected fumigated System 10 on ‘other mineral’ soil on account of the small yield improvement for System 10 although the sample size was small.
4.9. Local employmentThe overall labour requirement for strawberry crops is variable but may be high, up to 740 hrs/ha pre-picking
with an additional 79 hours per tonne picking, packing and transport to the retail outlet. The majority of labour for strawberry crops is in the form of casual labour, that is transient and from outside the local community thus local employment opportunities associated with strawberry production is lower, up to 162 hrs/ha. Those strawberry production systems that required greatest labour input by the grower or core farm staff are the protected crops in which tunnel erection and maintenance constitutes a large proportion of the input. The application of agro-chemicals required the second greatest proportion of grower labour then bed preparation thus integrated crops had greater requirements than the organic systems.
Seasonal labour is required for fruit harvest since it is not a mechanised process as for arable crops. It is required in all systems but is subject to legal requirements such as the The Gangmasters (Licensing) Act 2004. Many seasonal workers within the strawberry industry are part of The Seasonal Agricultural Workers Scheme (SAWS) that employs students from outside of the European Economic Area to work in UK agriculture for up to 6 months. The seasonal nature and large number of labourers required over a short time scale make recruitment of a local workforce difficult since the labour requirement cannot be sustained throughout the entire year. Thus the summer labour opportunities are suited for workers with other commitments during the year such as students or those seeking just part-time employment. Many rural communities are remote and thus alternative employment opportunities during non-harvest periods is low and as a consequence, much of the local younger workforce has sought employment in areas external to the local community. This is reflected in that 49% of the population employed within agriculture, forestry and fishing are aged 45 years or above compared with 32% for all other occupations. If local labour does not exist then there is no option but to import labour from external sources. Labourers participating in the SAWS are likely to be in good health and not require such high levels of health treatment as with older workers or those who have families with young children so pressure on local resources for the duration of the contracts of the seasonal workers are likely to be negligible. The seasonal labourers are provided with accommodation but will spend a proportion of their wages within the local community although the short term nature of the contracts are likely to mean that they will not be eligible to pay income tax. Labour within agriculture is considered to provide labour within the ancillary industries (transport, processing and marketing) on a ratio of 1:1 (Defra, 2005). The greater labour requirements for strawberry crops relative to other crops, arable crops in particular, is likely to provide greater levels of employment within the local community. In Herefordshire the rural economy has a limited manufacturing base but a well developed service sector, particularly in food and tourism. The England Rural Development Plan (ERDP) for the Region considers it important to produce a wide variety of locally grown food crops for marketing within the food and tourism sectors. Soft fruit crops, such as strawberries, would potentially increase the diversity of crops grown within the region. Within the South-East, the development and promotion of local products and local markets was listed within the ERDP for the region of which strawberries could be an important component.
4.10. Visual impactProtected strawberry crops require the use of plastic covered polytunnels that cover the entire crop at
certain times during the growing season. They are however temporary structures and the plastic cover is removed during periods when not required. The coverage of areas in excess of 3 or 4 ha potentially has a great visual impact on the environment as a result of reflection from the plastic surface and its light colour. It is difficult to quantify exactly the visual impact since the land where each crop is grown will have different topography and vegetation. The visual impact is related to the number of individuals that will see the structure and the perceived impact by that individual. The probability of the former is increased by the nature of the terrain, the proximity of roads and volume of traffic and the presence of features that attract visitors, for example heritage sites or nature reserves, in addition to the size of the structure. The latter is subjective and is related again to the size of the structure but also the landscape within which it is placed. An area considered scenic will, in all probability, arouse a greater negative response to the presence of the structure than an already intensively managed landscape with the presence of other structures. The ‘visual absorption capacity’ or ‘concept of scenic background’ refers to the nature of the backdrop to a view and the extent to which the structure is visible against it (Hernández et al., 2004). The backdrop may be predominantly sky, sea or land and each is important in the determination of the contrast, the sharpness of outlines and continuity of the landscape relative to the structure. A structure that breaks the horizon may be seen from many different angles and from a greater distance in addition to breaking an important
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landscape definition. A structure that has a backdrop of land tends to be more easily absorbed by the landscape with a greater associated continuity to the view. The South East is the most developed region of the UK outside London and approximately one third of the region is classified as Area of Outstanding Natural Beauty. The visual impact of polytunnels has potential to be greater in this region than the East of England where the population is lower and the land flatter. A Voluntary Code of Practice, that sets out guidelines with respect to the siting of polytunnels, has been drawn up by Herefordshire council in conjunction with growers who use polytunnels. The code includes a checklist that the grower is required to complete 3 months before the tunnel is erected that ensures the local authority, neighbours and the local parish council have been informed. The visual impact may be mitigated with consultation and planning though it will for some growers, limit the areas in which they may grow strawberry crops. This may have implications for the length of rotation of crops and reduction in the use of soil fumigants.
4.11. Sustainability profiles.Of the systems considered, the most sustainable overall minimised inputs and environmental outputs while
maintaining high yields. These included the organic crops, the System 4 (no crop first year) and the summer planted integrated systems in the examples studied. Methods of strawberry crop production are limited by soil quality and the presence of soil borne pathogens such as Verticillium that will impact the growers choice of system on a particular site. Growers test the soil before a decision to fumigate is taken however where Verticillium exceeds thresholds fumigation will be essential if an economically viable crop is to be produced. Organic systems do not have the option to chemically fumigate although steam sterilisation may be an option but this also incurs a high energy cost and will have a detrimental impact on soil fauna. Yields and therefore performance per tonne may be highly subject to site. The System 4 (no crop first year) performed well however this system requires a rotation in the region of 20 years and thus will only be practical for growers with large areas of land. It is also worth noting that this crop did not use a plastic mulch but instead suppressed weeds with herbicides during the first year. The crop was grown on a sand soil that is less fertile than, for example, a clay soil. To use such a system on more fertile soils may have increased weed problems and require a greater number of herbicide applications. A years income is also foregone on account of no harvest during the first year however the initial capital outlay is much lower than for other crops since mulch, tunnels, fumigation and irrigation are not used. The non-fumigated protected System 3 and non-fumigated non-protected System 4 had a higher performance per ha than the fumigated protected System 1 and fumigated non-protected System 2. They do not perform as well as the organic crops on account of higher ecotoxicity scores, the non-recycling of nutrients and greater risk of soil erosion during the winter of the first crop. Although the non-fumigated System 3 also achieved reasonable yields and had a reasonable corresponding sustainability profile per tonne, the combination of non-protection and non-fumigation appears to drastically reduce yields, for example in System 4. It is worthwhile to note that non-protected organic crops are not grown within the UK on account of low yields rendering them economically unviable. On a per ha basis, this was the system that had the greatest overall sustainability profile. On a per tonne basis however, such crops do not perform well or in the case of the non-protected organic system, not at all. The use of chemical fumigation confers extra flexibility with respect to sites that crops may be grown although it eliminates options such as organic production. The summer planting of crops in which two maincrop yields are obtained appears to be a good option for maximising yield while minimising inputs. Of the fumigated systems, the summer planted non-protected System 2 had increased yields but did not require the high energy inputs associated with protected crops. Regional variations in climate however, such as mean weekly temperature and rainfall, may also have an impact and cooler wetter regions may benefit more from the use of protection. No relationship between yield and region in non-protected crops was apparent for the examples studied however the sample size was small. Summer planted non-protected crops as a system may be of more benefit to growers in the South-East or East of England, particularly with respect to water use efficiency. Because there is no protection, there is added flexibility to the siting of such crops where visual impact may be important, principally the highly populated South-East region. The ecotoxicity of this system is greater than the other systems although by a relatively small percentage. No examples were available for the yields obtained with respect to non-fumigated summer planted crops and this would be interesting to obtain data for and conduct an assessment. Container crops, coir table crops in particular, require increased materials to be imported into the production system and thus per ha, their sustainability profile is reduced. Energy use and GHG emissions associated with transportation and fertiliser manufacture in addition to water use were lower for the peat media while nutrient use efficiency was greater. As a result, the sustainability profile of the peat container system was improved relative to the coir container system for the criteria selected however the profile does not account for the potential detrimental impacts associated with the removal of peat. English Nature (2005) have expressed concern that peat extraction results in the loss of sensitive natural habitats. The formation of peat takes hundreds of years thus its removal for short term use, 2 years in this case, may not be considered sustainable. Coir is a by product of coconut crops and thus produced within a short time period. It would be a more sustainable substitute if the nutrient requirements were lower. Other potential media were not assessed within the scope of the current study but any that do not require large mineral N inputs and transportation over large distances would in all probability improve the sustainability profile of container crops. For Junebearer crops per tonne the performance of the coir system is only superior to a small number of other systems for one crop. It is interesting to note that many growers do not produce container crops, coir crops in particular, for more than one crop although the materials will be re-used for a second crop. In general, most soil grown crops have a greater sustainability profile
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than container crops provided more than one crop is produced. The systems may be further grouped with respect to preference based on their sensitivity to site as follows:1) unlimited land for a long rotation: Junebearer System 4 (no crop first year), protected organic production
System 5; everbearer protected organic production System 12.2) limited land available and reduced option for rotation: Junebearer summer planted fumigated non-protected
System 2; summer planted fumigated protected System 1 (no protection second year); everbearer fumigated non-protected System 11.
3) poor soil quality: Junebearer protected container grown peat System 7; everbearer protected container grown peat System 13.Nitrogen leaching is likely to be low during the growth of the strawberry crop although since much of the
leaching is from the fallow alleys between the beds, the maintenance of a low SNS index before use of a site for strawberry production will minimise the risk of leaching from such areas. Those growers that used rotation stated the use of winter wheat within the rotation that leaves a low SNS index of 1, thus leaching risks are reduced. The presence of fallow uncultivated areas between crop rows and the accumulation of nitrate in the upper soil profile under the plastic mulch has implications for nitrate loss after removal of the crop, particularly crops grown for two or three seasons. The undertaking of tillage operations upon removal of the crop may mineralise increased quantities of N relative to a crop of a single years duration. A Junebearer crop will be removed during late July and allow the sowing of an early autumn sown crop that may remove some of the nitrate from the soil profile. An everbearer crop is likely to be removed at the end of September or later that potentially does not allow establishment and as greater removal of nitrogen by a following crop. The quantification of nitrate loss after removal of strawberry crops may be required. The coir grown Junebearer crops that apply large quantities of mineral fertiliser had the lowest sustainability scores per ha and per tonne for two crops. The N and P surplus criteria upon which their performance was poor has potential to be modified since the media in which the crops are grown may be spread away from the production area thus re-distributing nutrients. Many growers apply the media to the seedbed after crop removal which potentially results in the application of a large quantity of N during the late summer or autumn. The area over which the media is applied, the application rate of N/ha, and the timing should be treated as for Good Agricultural Practice for the application of fertiliser.
For the weighted indices based on the spatial scale of their impact the less energy intensive non-protected systems improved in environmental performance, however the decrease in margins negated this somewhat. The impact of recycling plastic in the protected systems in particular was highlighted.
Strawberry production in Spain differs by season with the planting of the crop during the winter and harvest from late January to early June that gives a longer season than the in the UK. The main difference is the small number of growing systems within Spain and the replacement of the crop every year, there is no option not to fumigate since crops are continuous and protection is always used. The inputs that last the crop lifetime such as mulch, bed preparation and fumigation last one crop as opposed to two or three within the UK. Yields per ha are higher on account of greater planting densities but a greater nutrient requirement is required coupled with the sandy soil that also increases the irrigation requirement. Loss of N to the ground water has an increased risk. The social impact of the strawberry industry within the Huelva region is far greater than within the UK since production is concentrated into one area and the town of Huelva contains businesses that service the strawberry industry. The flat, sparsely populated terrain results in a reduced visual impact and since the majority of the inhabitants are associated with the industry, complaints with respect to polytunnels less likely than within the UK.
4.12. Summary and conclusionsA balance must be achieved between minimising inputs to the system overall while maintaining reasonable
yields so that per tonne of class 1 fruit produced, environmental inputs and outputs remain low. Most strawberry crops within the UK are grown under protection and with soil fumigation. The main issues surrounding such methods of strawberry production are related to energy use, GWP, ecotoxicity, water use and visual impact. The importance of energy conservation was recently highlighted in The Energy White Paper: Our energy future - creating a low carbon economy published in 2002. The Kyoto Treaty commits industrialised nations to a reduction in GHG emissions, in particular Carbon Dioxide, by 5.2% below their 1990 levels over the next decade (Carbon Trust, 2004). All soil grown crops improve their energy efficiency and GHG emissions per crop with the production of a second or third crop. The production of N2O from de-nitrification during strawberry crop production is low in the integrated systems. The recycling of plastic offers the opportunity to reduce energy inputs and GHG emissions for most systems, the protected soil grown systems in particular. The ecotoxicity scores are relatively high in comparison to other crops but represent a worse case scenario. It should be borne in mind that all growers interviewed use Integrated Pest Management and only spray as necessary in response to crop thresholds being exceeded and use beneficial insects whenever possible. Actual scores are likely to be less during most years however, given the number of potential treatments required, the monitoring of strawberry crops and minimisation of sprays is essential. The Water Act 2003 aims to improve water conservation. Improvements in water use efficiency by, for example, monitoring the requirement of the crop as opposed to the maintenance of soil field capacity has important implications for strawberry production, particularly in the East of England and the South-East. The East of England represents the driest region within the UK while in the South-East, the relatively low rainfall in addition to the high population density has a correspondingly high demand for water resources. Both the Thames and Anglian Water Regions license a similar or greater volume of water extraction than the quantity of rainfall during periods of drought. Even in the West Midlands, that has a higher mean annual rainfall,
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there is a concern that the groundwater from some aquifers within the region is abstracted at an unsustainable rate, with serious reductions in surface water flows and the drying up of wetlands. It is noted that some growers have their own reservoirs that are charged during the winter months to maintain supply throughout the summer without depletion of groundwater or river flows. For these growers, the impact of strawberry production on water resources is small. The visual impact associated with strawberry production is a contentious issue. The Rural Development Programs for Herefordshire and Kent cite increased tourism as one means of achieving sustainable rural communities. Polytunnels have been criticised for potential detrimental impacts on tourism although this as yet, does not appear to have been proven. The mitigation of visual impact with for example anti-glare polyethylene tunnel covers and the siting of tunnels behind screens of, for example, trees have important implications for reducing the impact of strawberry production.
In 1991 Europe adopted the Nitrates Directive (91/676/EC) that resulted 8% of land within the UK designated as Nitrate Vulnerable Zones. This area was increased by a further 47% after a second consultation in 2001 to give a total designated area of 55%. Seventeen of the 68 NVZs occur in the East of England region, with 11 in the West Midlands and 9 in the South-East. Nitrogen loss to leaching during production of strawberry crops is likely to be low thus not an issue although improvements in the irrigation strategy may reduce losses further. The growing of a crop on the site that leaves a low SNS index before the strawberry crop and planting an early sown autumn crop post harvest may minimise the risk of N losses further. Soil erosion from rainfall was also predicted to be low although the use of straw mulch within the alleys simultaneously to plastic mulch and protection with polytunnels is key in preventing run-off during heavy rainfall. Significant areas of the West Midlands, particularly in Herefordshire, are catagorised as ‘greatest risk’ and ‘intermediate risk’ in the MAFF publication "Controlling Soil Erosion - A Manual for the Assessment and Management of Agricultural Land at Risk of Water Erosion in Lowland England (Annex B)". The production of strawberries within such areas are unlikely to increase the risk of erosion if straw mulch is applied to the alleys immediately after plastic mulch and before the erection of polytunnels and they are carefully sited to avoid steep gradients. Compared to most crops, the potential employment associated with strawberry production is high although much of it is likely to be sourced from outside the local community as seasonal labour. The labour supplied to local contractors and farm staff is still however likely to be greater than for most other crops. This may be of particular importance in the more remote production areas such as parts of the East of England and the West Midlands. The ERDP for the West Midlands and the South-East list the growing of diverse local produce to be sold locally as an objective in the development of sustainable rural communities. Strawberry production would offer potential to contribute to this objective.
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References to published material9. This section should be used to record links (hypertext links where possible) or references to other
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