2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.plant-soil.com J. Plant Nutr. Soil Sci. 2011, 174, 311–320 DOI: 10.1002/jpln.201000178 311 Site-specific fertilizer recommendations for oil palm smallholders using information from large plantations Michael J. Webb 1 *, Paul N. Nelson 2 , L. Gary Rogers 3 , and George N. Curry 4 1 Commonwealth Scientific and Industrial Research Organisation, Land and Water, Australian Tropical Sciences and Innovation Precinct, James Cook University, Douglas, Queensland 4814, Australia 2 School of Earth and Environmental Sciences, James Cook University, Cairns Queensland 4870, Australia 3 Runge Limited, Level 12, 333 Ann Street, GPO Box 2774, Brisbane, Queensland 4001, Australia 4 School of Social Sciences and Asian Languages, Curtin University, GPO Box U1987, Perth, WA 6845, Australia Abstract Provision of appropriate fertilizer recommendations to smallholder farmers is becoming increas- ingly important, for reasons of food security, economic viability, and the need to maintain soil fer- tility. Oil palm is one of the most important crops in the humid tropics, but smallholder growers (< 10 ha) typically have low yields, largely due to inadequate fertilizer inputs and/or incomplete harvesting. It is difficult to produce appropriate fertilizer recommendations for the smallholder growers, due to their large numbers and small farm sizes. In this work, we developed a way of transferring to smallholder growers the fertilizer recommendations that have been developed for nearby plantation fields using large fertilizer trials. The study site was in West New Britain Pro- vince, Papua New Guinea, and transfer of information was done using a geographic information system and maps of plantation fields, smallholder blocks, and soil types. The soil-map-unit descriptions were interpreted, and a unified classification system was derived. Then, fertilizer recommendations that had been made on a field-specific basis for the large plantations were allocated to soil types and thereby to individual smallholder blocks. In this way, block-specific fer- tilizer recommendations were made for more than 4000 individual smallholders. The procedures used were developed into a conceptual framework which is transferable to other regions. Recommendations can be updated as new information becomes available on smallholder block locations or plantation fertilizer recommendations. Key words: geographical information systems / soil maps / soil fertility / nucleus estate smallholder scheme Accepted January 7, 2011 1 Introduction Globally, and particularly in the tropics, rising population pres- sure is making it increasingly necessary for food- and cash- crop production to become more intensive and efficient in the use of inputs (Wadley et al., 2006). Intensification of land use can lead to soil-fertility decline (Maconachie and Binns, 2006; Bailey et al., 2009; Hartemink, 2005); and often, even when fertilizer is used, it may not be sufficient to replace losses or balance other forms of supply. To maintain soil nutrient status at a particular level, nutrients lost in the crop and through other pathways must be replaced. In commercial practice, such replacement is only regarded as necessary when crops begin to respond to individual nutrient additions. This is espe- cially important if nutrient availability is already low in relation to crop demand. However, producing the most appropriate fertilizer recommendations in terms of type, timing of applica- tion, amount, and balance is challenging due to variability in soils, climate, crop management, and the large number of smallholder farmers with limited resources and technical support pursuing a diverse range of crop-management strate- gies. While these challenges have been addressed in some regions and for some crops (Schnier et al., 1997; Das et al., 2009; Haefele and Konboon, 2009), there has been little attention to improving fertilizer recommendations for small- holder oil palm growers. The oil palm industry is important for rural incomes throughout the humid tropics, and some char- acteristics of its structure could be utilized for improving fertili- zer recommendations for smallholders. Palm oil is an important agricultural commodity globally and is likely to remain so in the future (Corley , 2009). Worldwide, about 48 Mt of palm oil (crude palm oil and palm kernel oil) were produced in 2008 (Global Oils and Fats Business Maga- zine, 2009) from an estimated 13 Mha (calculated from Cor- ley , 2009 and USDA, 2007). Of this global production about 20 Mt (41%) and 22 Mt (46%) were produced by Malaysia (Global Oils and Fats Business Magazine, 2009) and Indone- sia (calculated from USDA, 2007), respectively. Palm oil is produced from the fruit of the oil palm (Elaeis guinensis Jacq.), which is cultivated by corporate and individual growers. Smallholder growers, who typically cultivate < 10 ha, account for 37%–40% of the area under oil palm and contrib- ute to about 33% of total palm oil production (Vermeulen and Goad, 2006). The mismatch between percentage area planted and percen- tage contribution to palm oil production represents a “yield- * Correspondence: Dr. M. J. Webb; e-mail: [email protected]
Site-specific fertilizer recommendations for oil palm smallholders usinginformation from large plantationsMichael J. Webb1*, Paul N. Nelson2, L. Gary Rogers3, and George N. Curry4
1 Commonwealth Scientific and Industrial Research Organisation, Land and Water, Australian Tropical Sciences and Innovation Precinct,James Cook University, Douglas, Queensland 4814, Australia
2 School of Earth and Environmental Sciences, James Cook University, Cairns Queensland 4870, Australia3 Runge Limited, Level 12, 333 Ann Street, GPO Box 2774, Brisbane, Queensland 4001, Australia4 School of Social Sciences and Asian Languages, Curtin University, GPO Box U1987, Perth, WA 6845, Australia
AbstractProvision of appropriate fertilizer recommendations to smallholder farmers is becoming increas-ingly important, for reasons of food security, economic viability, and the need to maintain soil fer-tility. Oil palm is one of the most important crops in the humid tropics, but smallholder growers(< 10 ha) typically have low yields, largely due to inadequate fertilizer inputs and/or incompleteharvesting. It is difficult to produce appropriate fertilizer recommendations for the smallholdergrowers, due to their large numbers and small farm sizes. In this work, we developed a way oftransferring to smallholder growers the fertilizer recommendations that have been developed fornearby plantation fields using large fertilizer trials. The study site was in West New Britain Pro-vince, Papua New Guinea, and transfer of information was done using a geographic informationsystem and maps of plantation fields, smallholder blocks, and soil types. The soil-map-unitdescriptions were interpreted, and a unified classification system was derived. Then, fertilizerrecommendations that had been made on a field-specific basis for the large plantations wereallocated to soil types and thereby to individual smallholder blocks. In this way, block-specific fer-tilizer recommendations were made for more than 4000 individual smallholders. The proceduresused were developed into a conceptual framework which is transferable to other regions.Recommendations can be updated as new information becomes available on smallholder blocklocations or plantation fertilizer recommendations.
Key words: geographical information systems / soil maps / soil fertility / nucleus estate smallholder scheme
Accepted January 7, 2011
1 Introduction
Globally, and particularly in the tropics, rising population pres-sure is making it increasingly necessary for food- and cash-crop production to become more intensive and efficient in theuse of inputs (Wadley et al., 2006). Intensification of land usecan lead to soil-fertility decline (Maconachie and Binns, 2006;Bailey et al., 2009; Hartemink, 2005); and often, even whenfertilizer is used, it may not be sufficient to replace losses orbalance other forms of supply. To maintain soil nutrient statusat a particular level, nutrients lost in the crop and throughother pathways must be replaced. In commercial practice,such replacement is only regarded as necessary when cropsbegin to respond to individual nutrient additions. This is espe-cially important if nutrient availability is already low in relationto crop demand. However, producing the most appropriatefertilizer recommendations in terms of type, timing of applica-tion, amount, and balance is challenging due to variability insoils, climate, crop management, and the large number ofsmallholder farmers with limited resources and technicalsupport pursuing a diverse range of crop-management strate-gies. While these challenges have been addressed in someregions and for some crops (Schnier et al., 1997; Das et al.,2009; Haefele and Konboon, 2009), there has been littleattention to improving fertilizer recommendations for small-
holder oil palm growers. The oil palm industry is important forrural incomes throughout the humid tropics, and some char-acteristics of its structure could be utilized for improving fertili-zer recommendations for smallholders.
Palm oil is an important agricultural commodity globally andis likely to remain so in the future (Corley, 2009). Worldwide,about 48 Mt of palm oil (crude palm oil and palm kernel oil)were produced in 2008 (Global Oils and Fats Business Maga-zine, 2009) from an estimated 13 Mha (calculated from Cor-ley, 2009 and USDA, 2007). Of this global production about20 Mt (41%) and 22 Mt (46%) were produced by Malaysia(Global Oils and Fats Business Magazine, 2009) and Indone-sia (calculated from USDA, 2007), respectively. Palm oil isproduced from the fruit of the oil palm (Elaeis guinensisJacq.), which is cultivated by corporate and individualgrowers. Smallholder growers, who typically cultivate < 10 ha,account for 37%–40% of the area under oil palm and contrib-ute to about 33% of total palm oil production (Vermeulen andGoad, 2006).
The mismatch between percentage area planted and percen-tage contribution to palm oil production represents a “yield-
gap” between smallholders and large-scale plantations. It iscommonly believed by the oil palm industry that the lowerproduction by smallholders can, among other things, beattributed to nutrient deficiencies and ineffective nutrientmanagement—a circumstance that has been observed by uson many occasions whilst working within the industry. There-fore, methods are needed to improve smallholder fertilizermanagement in order to improve productivity (and farmerincomes) from land which is becoming increasingly underpressure.
Oil palm is frequently grown in a “nucleus estate” arrange-ment, in which a large company owns a mill and plantationsand also purchases crop from surrounding smallholder farm-ers (Hasnah et al., 2004). The milling/plantation companiesusually have sufficient income and space to carry out fertilizertrials and base their fertilizer management on trial results,leaf nutrient analysis, and monitoring of nutrient-deficiencysymptoms. However, the surrounding smallholder farms aregenerally not large enough for such research or monitoringprograms to be considered viable. Furthermore, when trialsare carried out on smallholder farms they are often difficult tomanage and interpret due to high variability in managementpractices among farmers and through time. Consequently,smallholders usually receive generic fertilizer recommenda-tions based on plantation trials, which are not necessarilyoptimal for their situations.
Optimum economic and sustainable oil palm yields can onlybe achieved with the judicious use of fertilizer (Goh et al.,2003), and nutritional constraints are a major limitation to pro-ductivity. In oil palm, as in other crops, fertilizer recommenda-tions are based on calibrated soil or leaf tests (Smith andLoneragan, 1997; McLaughlin et al., 1999). These tests usu-ally compare the soil or leaf nutrient concentration with a pre-determined “critical” concentration and are used to make fer-tilizer-application decisions. In the case of large commercialfarms with access to commercial soil- and plant-testing ser-vices, these critical concentrations are typically developedfrom field trials with a range of nutrient-application rates onsimilar soil types and under similar environmental conditionsto the field being tested. Such trials may involve one or morenutrients; the latter often being a factorial combination of alldeficient nutrients at several rates of application. Typically,recommendations will thus depend on soil type, climate, pre-vious fertilizer history, etc. Such trials are appropriate forlarge plantations to determine fertilizer-application rates eitherfor maximum yield (Foster, 2003) or, if fertilizer and other costsare included, for maximum profit (Webb, 2009, 2010).
In some plantations, however, appropriate trial information isnot available and thus recommendations are made on thebasis of leaf analysis, infrequent soil analysis, nutrient exportin product, deficiency-symptom scoring, past experience, andexpert opinion. Usually these recommendations are made ona field-by-field basis (fields are generally about 30 ha andbordered by access roads). Irrespective of how these fertili-zer decisions are made, such field-by-field information is usu-ally not available to smallholder farmers. Just as it would beconsidered inappropriate to have the same fertilizer recom-mendation for every field in a milling company’s plantation, it
is also inappropriate to have the same fertilizer recommenda-tion for every smallholder in a particular region without dueconsideration of edaphic and environmental conditions, andmanagement practices. In addition, as fertilizer represents asubstantial cost for smallholders, recommendations shouldbe based on known fertilizer responses to be economicallyjustifiable. Aside from planting and establishment costs, ferti-lizer purchases represent the bulk of production costs.Employment of hired labor is minimal with the vast majority ofsmallholders relying on family labor.
In this project, we set out to find a way in which the nutrient-management information generated in large plantations couldbe transferred to surrounding smallholder growers in the lar-gest oil palm–growing region of Papua New Guinea. We de-scribe how plantation fertilizer recommendations were trans-lated into block-specific fertilizer recommendations for small-holder oil palm growers, based on available soil maps,plantation maps, and smallholder maps using geographicalinformation systems (GIS) technology.
2 Case study setting
In Papua New Guinea, palm oil is the largest agriculturalexport, and oil palm production is an important source ofincome for rural communities. Oil palm cultivation occurs ona “nucleus estate” basis, where a company owns a mill andsurrounding plantations and also buys fruit from nearbysmallholder growers. A total of 133 400 ha are under oil palmcultivation in Papua New Guinea, of which 77 400 ha are incompany-owned plantations and 56 000 ha are in smallholderblocks (Curry and Koczberski, 2009). There are two largemilling/plantation companies and 18 600 smallholder blockssupporting over 180 000 people. Smallholders fall into threegroups: (1) settlers on land settlement schemes (LSS) whichwere first established in the 1960s to 1970s, (2) customaryrights purchase (CRP) blocks, which have been establishedby “outsiders” on customary land with the consent of the cus-tomary landowners, and (3) village oil palm (VOP) blocksestablished by customary landowners on their own land(Koczberski et al., 2001; Koczberski and Curry, 2003). LSSblocks are generally 6.0–6.5 ha whereas VOP and CRPblocks are typically 2 ha. Although CRP productivity is higherthan VOP productivity, company and extension data basesdo not differentiate between these two categories of growersso hereafter they are both referred to as VOP. Throughoutthe country, all types of oil palm smallholders are given tech-nical advice, including fertilizer recommendations, by officersof the Oil Palm Industry Corporation (OPIC). The fertilizerrecommendations are made by the Papua New Guinea OilPalm Research Association (PNGOPRA).
We have observed that nutrient deficiencies are prevalent inmany smallholder oil palm blocks in Papua New Guinea andmany palms exhibit nutrient-deficiency symptoms. Thus oftenyields are low, and consequently the ability of smallholders tomaximize income from oil palm blocks is also often low. Inrecognition of these deficiencies, fertilizer recommendationshave been made. However, the current practice is to make asingle fertilizer recommendation for all smallholders within a
particular area without consideration of edaphic or otherenvironmental conditions.
In this work, we focused on West New Britain Province wherenitrogen and magnesium deficiencies have been identified(Bleeker, 1983; Hartemink and Bourke, 2000). Here, twocompanies (New Britain Palm Oil Ltd. and Hargy Oil Palms
Ltd.) and 10 800 smallholders grow oil palm on a total of43 800 ha and 36 960 ha, respectively. Smallholders aregrouped into two project areas, Hoskins and Bialla (Fig. 1).Fruit from the Hoskins and Bialla project areas is collectedand purchased by New Britain Palm Oil Ltd. and Hargy OilPalms Ltd., respectively. Virtually all of the study area hassoils classified as Andisols (mostly Vitrands), formed in air-
Figure 1: Map of the study area showing the GIS layers for soil (lines), plantation fields (gray, upper map), and smallholder blocks (gray, lowermap). The numbers in bold refer to the original soil maps (Tab. 1). Smallholders to the west of Map 164 are associated with the Hoskins projectand those to the north-east of Map 164 with the Bialla project. Inset map shows location of study area (rectangle) within Papua New Guinea.
J. Plant Nutr. Soil Sci. 2011, 174, 311–320 Site-specific fertilizer recommendations for oil palm smallholders 313
fall or alluvially redeposited tephra (ash and pumice) ejectedwithin the last 6000 years (Bleeker, 1983; Machida et al.,1996). There are some small occurrences of soil developedon basalt. The area receives between 3500 and 4500 mmrainfall annually in a humid tropical climate.
Average yields are much higher in plantations than in small-holder blocks, with average harvested fresh fruit bunch yieldsof 24.1 t ha–1 y–1 in plantations, 14.4 t ha–1 y–1 for LSSgrowers, and 9.1 t ha–1 y–1 for VOP growers associated withHoskins project (Curry and Koczberski, 2006). These valueswere calculated from average monthly production over 5years from March 1998 to October 2003. However, individualsmallholders vary greatly in their fresh fruit bunch production,with some smallholders producing more than the neighboringplantation fields. The difference between plantations andsmallholders is at least partly due to nutrient management,although factors such as harvest completeness are alsoimportant (Koczberski and Curry, 2008). Water supply is non-limiting as periods of soil water deficit are rare and short(Banabas et al., 2008). The fertilizer recommendation formature palms for smallholders in the Hoskins area (4th yearsince planting and older) is 70, 85, or 120 kg N ha–1 y–1
(which, at the typical planting density of 120 palms per ha,equates to 0.6, 0.7, or 1.0 kg N palm–1 y–1). For smallholdersin the Bialla area, the mature-palm fertilizer recommendationis 0.6 or 0.8 kg N palm–1 y–1. The choice between those ratesis up to the grower, with the general assumption that growerswith more intensive management and higher productivity willapply a higher rate. Clearly, such an approach using a gener-alized recommendation for all smallholders in an area irre-spective of soil type or climate is inappropriate if there is adesire to maximize the efficient use of resources and mini-mize costs (economic and environmental).
In Papua New Guinea, there is a substantial amount of infor-mation that may be useful for estimating fertilizer responseson smallholder blocks. For example, soil maps, land-usemaps, and a large variety of remotely sensed data exist.However, the information has not been integrated nor used toguide land-management decisions such as fertilizer recom-mendations. In the soil maps, which were produced in the1960s to 1980s (Tab. 1), a variety of classification systemswere used, making it problematic to directly incorporate this
information into a useful planning or predictive tool for small-holders. There is a long record of nutrient analyses in planta-tion fields (soil and fronds) as well as data on yield responseto fertilizer application. Since 1990 there have been morethan 25 large, long-term (> 5 years) fertilizer trials in WestNew Britain Province, run by PNGOPRA. Thus the responseof oil palm to fertilizer application is well known on a field-by-field basis in the plantations. Because of their close proximityto plantation fields, many smallholder blocks share attributesin common with the plantation fields nearby: viz. soil type,aspect, climate, slope, etc. Although this case study isfocused on smallholders in Papua New Guinea, because ofthe similarity of the nucleus estate model for smallholder pro-duction in Malaysia and Indonesia, such a concept couldequally well be applied in the two largest palm oil–producingcountries.
3 Methodology
3.1 Concept and data acquisition
By using a GIS approach, smallholder blocks sharing thesame physical attributes with those of plantation fields couldbe assigned the same fertilizer recommendations. Thus, ifthere is information available on these physical attributes, thewealth of knowledge that has been used to derive fertilizerrecommendations for plantation fields could be applied tosmallholder blocks. It is recognized that many biotic and abio-tic factors other than physical attributes may influence anappropriate fertilizer recommendation. For example, thereare different fertilizer recommendations for immature andmature palms. The immature fertilizer recommendations fol-low a fixed formula not dependent on soil or palm monitoringand could be equally applicable to well-managed smallholderblocks. Thus, the concept presented here is most concernedwith the variable fertilizer recommendations applied to themature phase.
Once palms have reached canopy closure (start of maturephase), palm age is of little consequence with respect to re-sponse to management inputs. Other factors that could influ-ence yield, and thus fertilizer requirements are not consid-ered here (although incomplete harvesting, and its conse-quences are discussed later), as the concept is to make
recommendations which, under good management, producethe most profitable yield for smallholders. The concept pro-vides a means to set a target fertilizer recommendation thatwould provide smallholders with the best opportunity ofachieving maximum production in a well managed oil palmblock. The concept is to provide a long-term approachto increasing smallholder productivity through a managedinvestment in fertilizer (see discussion for a “stagedapproach”) although it does allow for modifications of thoserecommendations (see section 5).
To determine fertilizer recommendations outlined above, thephysical attributes of plantation fields were matched withthose of smallholder blocks using soil-map information. Eightsoil maps and accompanying documentation of oil palm–growing areas in West New Britain Province (Tab. 1) were ob-tained from the Department of Agriculture and LivestockLand Use Section. These maps were digitized, rectified, andsaved into a GIS as a single layer. The original individualmaps usually used natural water courses as boundaries. Inmost cases, these boundaries could be lined up seamlessly.However, in some cases, water courses had changed be-tween the times when mapping was done. In these cases,borders were “stitched” together as best as possible; usuallywith the most recent map dominating. The national soil mapof Papua New Guinea, which comprises part of the PapuaNew Guinea Resource Information System (PNGRIS), wasnot used for this work as it is of too broad a scale to beuseful.
Each unique mapping area polygon in the original maps wasassigned a map number and a soil type to create a uniquesoil-type identification. As each unique mapping area mayhave several soil types associated with it, the soil type as-signed was the dominant soil type for that unique mappingarea. Unique mapping areas were also assigned a soil profileform which is a more general soil description adopted bymany of the authors of the soil reports (Tab. 2). If a soil profileform was not provided in the original map, one was assignedaccording to the profile properties. Soil profiles and descrip-tions were confirmed during a field visit in April 2006 to physi-cally inspect the major soil types described in the variousmaps and reports.
Digital maps of 4342 smallholder blocks (Fig. 1) for West NewBritain Province were obtained from OPIC (Hoskins district)for Hoskins smallholders and from Hargy Oil Palms Ltd. forBialla smallholders. While GIS information was available for
all the plantation fields, less than half of the smallholderblocks had been geo-referenced. The geo-referenced small-holder blocks were all LSS blocks, and those not yet geo-referenced were mostly VOP blocks.
Digital plantation maps, supplied by New Britain Palm Oil Ltd.and Hargy Oil Palms Ltd., were combined into a single layer(Fig. 1). Plantation companies in Papua New Guinea manageoil palm fields according to management units (MUs) or leaf-sampling units (LSUs) which consist of one or more contigu-ous fields so similar in terms of soil, planting material, andpalm age that they can be considered a single entity for thepurpose of management. As MUs and LSUs are functionallythe same, the term MU will be used to refer to both. Planta-tion MUs were assigned a unique identification code and at-tached to the layer. When the soil, plantation field, and small-holder block layers were combined, it was clear that soil typesrun across, and are common with, both plantation and small-holders (Fig. 1).
Commonly, a fertilizer recommendation is made for each MUand that recommendation is applied to all plantation fieldswithin that MU. Thus fertilizer recommendations (N, P, K,Mg, B) for each MU were added to the plantation MU layer.For this work, the fertilizer recommendations used were themean of those made over the previous three years byPNGOPRA but the period considered could be changed asappropriate, especially if there is a sudden change in globalpalm oil prices or fertilizer costs (Webb, 2009, 2010).
3.2 Data analysis and production of fertilizerrecommendations
The soil maps were used to “split” the MUs from the planta-tion maps according to soil type. For each soil type, a fertilizerrecommendation was calculated using an area-weightedaverage of all MUs containing that soil type. Thus, each soiltype has a fertilizer recommendation based on the oil palmcompany’s fertilizer recommendations (Fig. 2).
The smallholder blocks were also “split” using the soil-typemap. Fertilizer recommendations for each smallholder blockwere then calculated from the area-weighted average of thefertilizer recommendation for the soil type underlying thatblock (Fig. 3). Where an exact match was not possible, arecommendation was made based on the closest smallholderblock which had a match, or the closest plantation field, as
Table 2: Soil-profile form (SPF) classification used in original maps.
SPF Description
Organic soils dominated by organic matter, conspicuous decomposed plant material throughout the upper 30 cm, organic-mattercontent greater than 20% in coarse soils and greater than 50% in clays
Regular soils dominated by mineral fraction with small if any textural differences with depth
Increasing soils dominated by mineral fraction with increasingly finer texture with depth
Contrast soils dominated by mineral fraction with a texture contrast between A and B horizons of at least 1.5 to 2 texture groups;increasingly finer texture with depth
Multiple soils dominated by mineral fraction with a disordered succession of layers with varying texture and abrupt horizons
J. Plant Nutr. Soil Sci. 2011, 174, 311–320 Site-specific fertilizer recommendations for oil palm smallholders 315
appropriate. Those smallholder blocks constituted less than3% of the 4342 blocks considered.
Smallholder recommendations for each nutrient were con-verted to units of fertilizer, rounded up to the next 0.5 kg (or0.05 kg for calcium borate), and displayed as maps (Fig. 4) orTables (Tab. 3) and distributed on Compact Disk® (CD) to themilling companies, OPIC, and PNGOPRA. The CD has auser-friendly interface which requires only basic computerskills to operate. Presentation in such a format allows usersaccess not only to the recommendations but also to originaldata (e.g., soil maps, satellite imagery, topographic maps,geological maps), derived maps (e.g., soil principal profileform), and other related information. Access to the informa-tion is driven completely by “buttons” and “pull-down” menus.
The CD operates on a range of Windows® operating systemsand includes the freely available program ProViewer®, whichallows viewing of spatial data without a full GIS program andwith minimal computer memory. Being cheap to produce andeasy to distribute, the CD format facilitates distribution ofupdated data sets. A more detailed account of the methodol-ogy can be found in Rogers et al. (2006).
4 Results and discussion
Through the process described above, it was possible tomake individual fertilizer recommendations for 4342 small-holders (Fig. 4, Tab. 3) based on existing data. Recommen-dations were possible only for blocks that had been geo-referenced (virtually all were LSS blocks) and were in theGIS. Management, including fertilizer application, tends to bemore intense in LSS than VOP blocks because LSS block-holders are more dependent on oil palm income than VOPproducers, who have access to more land and other sourcesof cash income (Koczberski and Curry, 2005). However, asmore smallholder blocks are included in the GIS system, thenumber of individual recommendations can be increasedaccordingly. The fertilizer recommendations shown in thisexample (Fig. 4) are in units of fertilizer (i.e., ammoniumchloride) mass rather than main element mass for conveni-ence of the extension officer and the smallholder. However,they can be in any units required; for example, other fertilizersbeing used (e.g., kg ammonium sulfate), or in terms of mainnutrient element (e.g., kg N) if fertilizer cost and source areyet to be determined.
This work relied on the existence of soil maps at an appropri-ate scale covering the area of interest. However, in manyparts of Papua New Guinea and the world, soil maps are notavailable at that level of detail. Nevertheless, digital elevationdata, available globally from the shuttle radar mission, can beused to improve the precision of broad-scale soil maps, andthis has recently been done for Papua New Guinea (Bryanand Shierman, 2008). The improved map might be used forsimilar purposes in parts of the country where more detailedsoil maps are not available. Similarly, the framework allowsother spatially defined information, such as climate or aspect,to be incorporated where appropriate. Even so, soil mapsmight not always provide sufficient detail for fertilizerresponses to be estimated accurately, due to smaller-scalevariations in soil fertility. For example, management-inducedgradients of declining soil fertility and fertilizer response with
Figure 2: Fertilizer recommendations for soil-map units (curvedpolygons) were derived from area-weighted averages of the MUs(rectangular polygons) overlapping each soil type unit. The numbersrefer to kg N palm–1 y–1.
Figure 3: Fertilizer recommendations for each smallholder block(rectangular polygons) were derived from area-weighted averages ofsoil-map unit (curved polygons) fertilizer recommendations under-lying each smallholder block. The numbers refer to kg N palm–1 y–1.
Table 3: Typical fertilizer recommendation by smallholder block. AC is ammonium chloride (another source of N can be substituted for ACaccording to price), DAP is diammonium phosphate, KIE is kieserite (magnesium sulfate), MOP is muriate of potash (potassium chloride), andCaB is calcium borate. “Matchtype” describes the information used to match a smallholder block with a plantation field. If possible, the dominantsoil type (Soil 1) was used to make the match; if not possible, a broader description, the soil-profile form (SPF) was used.
distance from the homestead are common in Africa (Tittonellet al., 2007; Zingore et al., 2007). While within-block variabil-ity in soil fertility is bound to exist in smallholder oil palmblocks, the framework used here represents a first step awayfrom regionally uniform fertilizer recommendations to muchmore locally specific recommendations.
If smallholders also had access to leaf-tissue nutrient analy-sis, some of these issues could be addressed more appropri-ately. Even without tissue analysis, experienced extensionofficers may be able to identify nutrient limitations in small-holder blocks. Ideally, corrective measures to ensurebalanced nutrition in smallholder blocks would be undertakenbefore the recommendation concept developed here isadopted. However, access to such expertise is often so lim-ited in countries like Papua New Guinea that personal visitsand subsequent individual recommendations by experiencedextension officers are not possible. Indeed, considering thecurrent number of smallholder blocks with respect to thenumber of extension officers in Papua New Guinea, it wouldonly be feasible for an officer to visit each block once every2 years. Thus, the approach taken in the concept developedhere is to make the best possible recommendations using thelimited information available, but recognizing that, with addi-tional resources, other approaches may provide more indivi-dualized recommendations.
A major part of the work involved obtaining copies of the origi-nal soil maps, digitizing and geo-referencing them, andassigning soil types to soil polygons. However, this work onlyneeds to be done once. The subsequent processing is simplya procedural matter, which could be simplified by some
degree of automation. Therefore, if plantation fertilizer recom-mendations change or as more smallholder blocks are geo-referenced, the fertilizer recommendations can be easilyupdated.
The outputs were produced in both table and map format,each possessing different advantages. The table allows eachsmallholder or extension officer to look up the recommenda-tions for a specific block (Tab. 3). The map of recommenda-tions allows plantation staff and extension officers to look atfertilizer requirements across a region. For example, it isclear in the sample of smallholder blocks presented here(Fig. 4) that there is a spatial trend in nitrogen requirement;generally increasing from northwest to southeast. Further-more, as the plantation companies purchase fertilizer onbehalf of smallholders, such an analysis assists in predictingfertilizer and transport needs.
As fertilizer recommendations for plantations are doneannually, it would be possible to update fertilizer recommen-dations for smallholders each year. However, it is probablymore sensible to use a running average of plantation fertilizerrecommendations over the last few years to obtain a long-term recommendation, as smallholders currently do not havethe advantage of diagnostic soil and tissue sampling to makefine adjustments to fertilizer inputs. In the future, if leaf-tissuetesting were to be carried out on smallholder blocks, then theresults could be used to refine fertilizer recommendationsusing the framework described here. Smallholders who man-age their blocks well and harvest all of their crop would bemost likely to benefit from the additional expense of tissuetesting.
Figure 4: Example of a map ofsmallholder blocks with fertilizerN recommendations in 0.5 kgincrements of ammonium chlor-ide (only a portion of the totalmap is shown). The 0 (white)category mostly refers to blocksfor which it was not possible tomake a match with the planta-tion soil types and therefore notpossible to make a reliablerecommendation.
J. Plant Nutr. Soil Sci. 2011, 174, 311–320 Site-specific fertilizer recommendations for oil palm smallholders 317
There are some considerations which should be made ifemploying this conceptual framework for making fertilizerrecommendations. Firstly, not only can such a framework beused to provide fertilizer recommendations, it can also beused to provide information on potential yields, as sensiblecomparisons can now be made with yields from appropriateplantation fields. Secondly, if a smallholder’s current yieldsare well below those of the neighboring plantation, then aphased approach to increasing fertilizer application up to theplantation level should be implemented to avoid high initialcosts (fertilizer cost is immediate), creating disincentives toharvesting and block maintenance and delayed return oninvestment (increase in yields may take 2–3 years to be rea-lized). It is known that high rates of deductions for loan repay-ments can act as a disincentive to smallholders to investlabor in block maintenance and harvesting (Curry et al.,2007). Thirdly, smallholder yield data, plantation yield datafrom comparative fields, appropriate fertilizer rates, and fertili-zer costs can be used to inform smallholders of potentialreturns from appropriate fertilizer use and subsequent yieldincrease.
Crop responses to fertilizer applications also depend on lim-itations to yield that are not related to soil or landscape attri-butes. In many parts of the world, water limitation is the mostimportant other factor (Schnier et al., 1997; Haefele andKonboon, 2009), but in this part of Papua New Guinea wateris rarely if ever limiting. However, yields are often low dueto incomplete harvesting, which is common for a varietyof socioeconomic reasons, especially in VOP blocks(Koczberski and Curry, 2008). This has implications for theprofitability of fertilizer application. For example, there is nonet economic benefit of applying fertilizer in West New BritainProvince if only 25% of the crop is harvested and the freshfruit bunches price is low; at that level of harvesting, fertilizerapplication is only barely profitable even at high fresh fruitbunches prices (Fig. 5). The required price of fresh fruitbunches to break even for fertilizer use rapidly increases aspercent harvesting rate decreases (Fig. 5).
In cases where there is no yield response to fertilizer applica-tion, then it is likely that social factors are constraining thesupply of labor for block maintenance and/or harvesting. Insuch cases, fertilizer recommendations and deliveries forthese blocks could be suspended until labor constraints areovercome through appropriate extension interventions (for adiscussion of smallholder labor issues see Koczberski andCurry, 2008).
As most companies hold records of smallholder productivityto facilitate payment for crop, Harries and Benjamin (1991)have recommended that such crop records could be used toidentify and assist those who are under harvesting. Thiswould firstly facilitate adjustment of fertilizer recommenda-tions as suggested above, but more importantly, identifysmallholders who are not harvesting completely and thusalert extension officers of the need to investigate courses ofremedial action that could benefit the farmer.
It should be possible within 3 years of implementation of theframework to differentiate between farmers who are able torealize the benefits of fertilizer application as higher produc-tion (the high producers) and those who, for various socio-cultural reasons, are unable to realize fully the income gainsfrom fertilizer because of underharvesting. Thus, in future,fertilizer recommendations, while being tailored to edaphicand environmental factors, may also be able to accommo-date some of the socio-cultural factors affecting smallholderproductivity.
5 A logical plan for application of thisframework
The following is a suggestion on how the techniques devel-oped here might be used in a practical sense, with other infor-mation, to make sensible and profitable fertilizer recommen-dations for smallholders. The logical plan, like the decisiontool developed by Haefele and Konboon (2009), takes intoaccount non-soil factors influencing yield, and it could be latermodified to take account of other factors and other informa-tion (e.g., leaf nutrient analysis on smallholder palms), dis-cussed previously, when they become available.
(1) Use plantation fertilizer recommendations (averaged overthe last few years), soil maps, and GIS to provide initial fertili-zer recommendations.
(2) Use plantation data from comparative fields (already iden-tified as part of step 1) to estimate realistic potential yieldunder similar edaphic and climatic conditions. It is importantto attempt to estimate agronomic yield, rather than yieldassessed through weighbridge dockets as the latter willunderestimate the former because of issues unrelated to bio-logical productivity.
(3) Determine current (or average over a few years) yield ofthe smallholder block. Again it is important to account for non-agronomic factors such as “trading” crop between blocksand/or underharvesting. For this reason, as above, the millpurchase-records may not reflect individual block production.
Figure 5: Profitability of fertilizer use at different harvesting rates inrelation to farm gate price for fresh fruit bunches (FFB) in West NewBritain Province. Assumption: application of 2 kg ammonium chlorideper palm will result in a 5 t ha–1 y–1 increase in productivity; cost forammonium chloride is USD12.38 per 50 kg bag.
(4) Determine the increased returns to be gained if fertilizerrecommendations were followed. This would require evalua-tion of increased income (fruit) against increased costs (fertili-zer, loan repayment, labor—also see step 5 below), and thecompleteness of harvesting. Where incomplete harvestingoccurs, extension interventions might be required.
(5) Explore options for additional labor (see also Step 4above) to meet the increased demand (fertilizer application,weeding, pruning, harvesting, etc.) in balance with other eco-nomic and social commitments.
(6) Re-evaluate steps 4 and 5 above to determine a practicaland achievable harvested yield.
(7) Determine fertilizer requirements to achieve that har-vested yield consistently.
(8) Develop a financial and management strategy to imple-ment that plan. This will most likely involve a staged approachas suggested above to avoid excessive financial burden (fer-tilizer purchase and application, additional weeding, etc.)while waiting for the return on the investment to be realizedthrough increased yield, which may take 2–3 years. A stagedapproach could be achieved in a number of ways:
(a) Incrementally increase fertilizer to the whole block up tothe level determined in step 7.
(b) Incrementally increase the number of palms that receivethe full recommended level determined in step 7 until thewhole block receives that rate; most likely starting near theroadside where harvesting rates are usually higher.
Option (b) would most likely provide a visual and demon-strable response much more quickly (albeit to only a smallsection of the block) and thus be a stronger reinforcementthat the investment of resources was worthwhile.
6 Conclusions
The framework developed here enables production of fertili-zer recommendations for individual smallholder oil palmgrowers using existing biophysical information. Adoption ofthe suggested framework would provide more appropriatefertilizer recommendations at the level of the individualgrower than the current method of a single region-widerecommendation. More appropriate fertilizer recommenda-tions at this scale are likely to improve the efficacy of fertilizerapplication and the returns to growers. Whilst the frameworkrepresents a considerable improvement on the current sys-tem for fertilizer recommendations for smallholder farmers,there is scope for further refinement as social factors influen-cing farm management practices are taken into account.
Acknowledgments
This project was funded by the Australian Agency for Interna-tional Development (AusAID) through the PNG AgriculturalInnovations Grant Facility (AIGF), and supported by PNGO-
PRA and James Cook University. We are very grateful toPNGOPRA, OPIC, New Britain Palm Oil Ltd., Hargy OilPalms Ltd., and the following people for helping us carry outthe project. Ian Orrell and Frank Lewis helped design andimplement the project. Steven Kamis, Ben Darius, JohnKama, Reuben Sigi Taureka, Peter Tarramurry, and RichardTiamu helped with checking the soil maps in the field. Eliza-beth Kibikibi typed out soil map unit descriptions from the soilsurvey reports. Angela Pollet gave GIS advice. Mike Hoare,Simon Lord, and Severina Betitis made New Britain Palm OilLtd. data available to us, and Graham King made Hargy OilPalms Ltd. data available to us. Thomas Betitis helped com-pile the soil maps, and Daniel Barth and Heiko Seitz didmuch of the digitizing. Thomas Fairhurst gave constructivecomments on the manuscript.
References
Aland, F. B., Searle, P. G. E. (1966): Soil survey of West New Britain.The Tiauru-Ala area. Department of Agriculture, Stock and Fish-eries, Port Moresby. 1 map (#164), 1 report.
Bailey, J. S., Ramakrishna, A., Kirchhof, G. (2009): An evaluation ofnutritional constraints on sweet potato (Ipomoea batatas)production in the central highlands of Papua New Guinea. PlantSoil 316, 87–105.
Banabas, M., Turner, M., Scotter, D. R., Nelson, P. N. (2008): Lossesof nitrogen fertiliser under oil palm in Papua New Guinea: 1. Waterbalance, and nitrogen in soil solution and runoff. Aust. J. Soil Res.46, 332–339.
Bleeker, P. (1983): Soils of Papua New Guinea. CSIRO and ANUPress, Canberra.
Bryan, J. E., Shierman, P. L. (comps.) (2008): Papua New GuineaResource Information System Handbook. 3rd edn., University ofPapua New Guinea, Port Moresby.
Corley, R. H. V. (2009): How much palm oil do we need? Environ.Sci. Policy 12, 134–139.
Curry, G. N., Koczberski, G. (2006): Social and cultural factors influ-encing smallholder production strategies in Papua New Guinea.Presented at the Scientific Advisory Committee Meeting of thePNG Oil Palm Research Association, September 7, 2006, PortMoresby.
Curry, G. N., Koczberski, G. (2009): Smallholder studies. Commercialsector/smallholder partnerships for improving incomes in the oilpalm and cocoa industries in Papua New Guinea. PNG Oil PalmResearch Association Annual Report for 2008, Dami ResearchStation, WNBP, Papua New Guinea.
Curry, G. N., Koczberski, G., Omuru, E., Duigu, J., Yala, C., Imbun,B. (2007): Social Assessment of the Smallholder AgricultureDevelopment Project. Report prepared for World Bank.
Das, D. K., Maiti, D., Pathak, H. (2009): Site-specific nutrientmanagement in rice in Eastern India using a modeling approach.Nutr. Cycl. Agroecosyst. 83, 85–94.
Foster, H. (2003): Assessment of oil palm fertiliser requirements, inFairhurst, T. H., Härdter, R.: Oil Palm: Management for High andSustainable Yields. Potash & Phosphate Institute, Potash & Phos-phate Institute of Canada, International Potash Institute,Singapore, pp. 231–257.
Global Oils and Fats Business Magazine (2009): Malaysian palm oil.Industry performance 2008, vol 6, issue 1 (Jan–March), 2009,available at: http://www.malaysiapalmoil.org/pdf/MPO_Industry_Performance_2008.pdf , accessed March 12, 2010.
J. Plant Nutr. Soil Sci. 2011, 174, 311–320 Site-specific fertilizer recommendations for oil palm smallholders 319
Goh, K.-J., Härdter, R., Fairhurst, T. H. (2003): Fertilizing formaximum return, in Fairhurst, T. H., Härdter, R.: Oil Palm:Management for High and Sustainable Yields. Potash & Phos-phate Institute, Potash & Phosphate Institute of Canada, Interna-tional Potash Institute, Singapore, pp. 279–306.
Haefele, S. M., Konboon, Y. (2009): Nutrient management for lowlandrice in northeast Thailand. Field Crop Res. 114, 374–385.
Harries, H., Benjamin, C. (1991): Smallholder oil palm productivitystudy. (ADB TA NO 790 PNG). Department of Agriculture and Live-stock Konedobu. Papua New Guinea.
Hartemink, A. E. (2005): Plantation agriculture in the tropics: environ-mental issues. Outlook Agric. 34, 11–21.
Hartemink, A. E., Bourke, R. M. (2000): Nutrient deficiencies of agri-cultural crops in Papua New Guinea. Outlook Agric. 29, 97–108.
Hartley, A. C. (no date): Map title – Soils map of Dagi-Kulu.Department of Agriculture, Stock and Fisheries, Port Moresby.1 map (#192).
Hartley, A. C., Aland, F. B., Searle, P. G. E. (1967): Soil survey ofWest New Britain. The Balima-Tiauru area. Soil Survey Report No.1, Department of Agriculture, Stock and Fisheries, Port Moresby.1 map (#176), 1 report.
Hasnah, Fleming, E., Coelli, T. (2004): Assessing the performance ofa nucleus estate and smallholder scheme for oil palm production inWest Sumatra: A stochastic frontier analysis. Agric. Syst. 79,17–30.
Koczberski, G., Curry, G. N. (2003): Sustaining production and liveli-hoods among oil palm smallholders: A socio-economic study of theBialla smallholder sector. Research Unit for the Study of Societiesin Change, Curtin University of Technology, available at: http://espace.lis.curtin.edu.au/archive/00000233/
Koczberski, G., Curry, G. N. (2005): Making a living: Land pressuresand changing livelihood strategies among oil palm settlers inPapua New Guinea. Agric. Syst. 85, 324–339.
Koczberski, G., Curry, G. N. (2008): Smallholder mobile card trial,Bialla oil palm project, West New Britain Province, Papua NewGuinea. Research Unit for the Study of Societies in Change, CurtinUniversity of Technology, available at: http://espace.lis.curtin.edu.au/archive/00002985/01/Bialla_MobileCardReport_FINAL_23July08.pdf
Koczberski, G., Curry, G. N., Gibson, K. (2001): Improving roductivityof the smallholder oil palm sector in Papua New Guinea. ResearchSchool of Pacific and Asian Studies, Australian National University,available at: http://espace.lis.curtin.edu.au/archive/00000235/
Machida, H., Blong, R. J., Specht, J., Moriwaki, H., Torrence, R.,Hayakawa, Y., Talai, B., Lolok, D., Pain, C. F. (1996): Holoceneexplosive eruptions of Witori and Dakataua Caldera volcanoes inWest New Britain, Papua New Guinea. Quaternary Int. 34–36,65–78.
Maconachie, R. A., Binns, T. (2006): Sustainability under threat? Thedynamics of environmental change and food production in peri-urban Kano, northern Nigeria. Land Degrad. Dev. 17, 159–171.
McLaughlin, M. J., Reuter, D. J., Rayment, G. E. (1999): Soil testing– Principles and concepts, in Perverill, K. I., Sparrow, L. A., Reuter,D. J.: Soil Analysis: An Interpretation Manual. CSIRO Publishing,Collingwood, pp. 1–21.
Murty, D. W. P. (1967): Navo land soil survey report. Department ofAgriculture, Stock and Fisheries, Port Moresby, 1 map (#166), 1report.
Murty, D. W. P. (1971): Soi land soil survey report. Department ofAgriculture, Stock and Fisheries, Port Moresby, 1 map (#167), 1report.
Rogers, L. G., Webb, M. J., Nelson, P. N. (2006): Site specific ferti-lizer recommendations to increase income of smallholder oil palmproducers in West New Britain Province, Papua New Guinea.Papua New Guinea Oil Palm Research Association, Kimbe, PapuaNew Guinea.
Schnier, H. F., Recke, H., Muchena, F. N., Muriuki, A. W. (1997):Towards a practical approach to fertilizer recommendations forfood crop production in smallholder farms in Kenya. Nutr. Cycl.Agroecosyst. 47, 213–226.
Smith, F. W., Loneragan, J. F. (1997): Interpretation of plant analysis:concepts and principles, in Reuter, D. J., Robinson, B.: Plant Anal-ysis: An Interpretation Manual. CSIRO Publishing, Collingwood,pp. 3–33.
Tittonell, P., Zingore, S., van Wijk, M. T., Corbeels, M., Giller, K. E.(2007): Nutrient use efficiencies and crop responses to N, P andmanure applications in Zimbabwean soils: Exploring managementstrategies across soil fertility gradients. Field Crops Res. 100,348–368.
Tyrie, G. R. (1986): Map title – Gaho-Kulu Area, West New BritainProvince. Department of Primary Industries, Port Moresby, 1 map(#505).
USDA (2007): Indonesia: Palm Oil Production Prospects Continue toGrow December 31, 2007, USDA-FAS, Office of Global Analysis,available at: http://www.pecad.fas.usda.gov/highlights/2007/12/Indonesia_palmoil/, accessed March 12, 2010.
Vermeulen, S., Goad, N. (2006): Towards a better practice in small-holder palm oil production. Natural Resource Issues Series No. 5.International Institute for Environment and Development. London,UK, available from www.iied.org
Wadley, R. L., Mertz, O., Chistensen, A. E. (2006): Local land usestrategies in a globalising world – managing social and environ-mental dynamics. Land Degrad. Dev. 17, 117–121.
Webb, M. J. (2009): A conceptual framework for determiningeconomically optimal fertiliser use in oil palm plantations withfactorial fertiliser trials. Nutr. Cycl. Agroecosyst. 83, 163–178.
Webb, M. J. (2010): Development of a fertiliser optimisation tech-nique using multi-nutrient factorial trials and leaf tissue nutrientanalysis in commercial oil palm plantations. 19th World Congressof Soil Science, Soil Solutions for a Changing World, August 1–6,2010, Brisbane, Australia, available at: http://www.iuss.org/19th%20WCSS/symposium/pdf/0817.pdf
Zijsvelt, M. F. W. (1977): Soil survey and land use potential of theKapiura-Dagi area, West New Britain. Research Bulletin No. 19.Department of Primary Industries, Port Moresby, 1 map (#441),1 report.
Zijsvelt, M. F. W., Torlach, D. A. (1975): Soil survey and land usepotential of the Ala-Kapiura area, West New Britain, Papua NewGuinea. Research Bulletin No. 17. Department of Agriculture,Stock and Fisheries, Port Moresby, 1 map (#440), 1 report.
Zingore, S., Murwira, H. K., Delve, R. J., Giller, K. E. (2007): Soiltype, management history and current resource allocation: threedimensions regulating variability in crop productivity on Africansmallholder farms. Field Crops Res. 101, 296–305.
