Optimizing greenhouse climate in tomatoesby André Kool, Green Q

Content

• Why focus on climate?

• What is a good greenhouse climate?

-Day-climate-Dissimilation -Night-climate

• 24-hr average temperature regulation• Speed of growth• Conclusion

1.Crop parameters (tomato)-Stretching of internodes, leafs, truss-stem-Colour of leafs (head) and fruits-Power of head and truss-Pollination and fruitsetting-Production and quality-Presence of diseases (f.e. botrytis)

2.Greenhouse parameters

-computer settings (basic settings & strategy)-realised climate, irrigation, fertilisation, CO2-”feel” the climate

Important subjects to check

1.Most problems with quality and production are caused by a badgreenhouse climate:• too small fruitsize (too less kg’s!!!)• fruitskin problems (cracking)• botrytis and other fungi-problems

Most problems can be prevented byoptimizing greenhouse climate!!!!

Why focus on climate?

• Irrigation and fertilisation are blamed for many problems……………………

• Irrigation and fertilisation are important, however……a good greenhouse climate enables the crop to take up water and nutrients.

• Water and fertilizers are taken up by evaporation of the crop.

• evaporation of crop is affected by greenhouse climate…………….

More reasons to focus on climate

• Cultivar is important, but many times blamed for problems undeserved.

• In many cases “bad” properties of a cultivar can be (partly) reduced by optimizing climate. Especially fruitskin problems

Still more reasons to focus on climate

Before answering this question first some basic plant physiology

Photosynthesis=assimilation=production of sugar=growth

Only take place during day time (sunrise-sunset)

A good day-climate is the most important factor for a optimal growth.

What is a good greenhouse climate?

Bron:D. Klapwijk

Bruto fotosynthesis

At high light level

At low light level

Bron:D. Klapwijk

Dissimilation

dissimilation

Netto fotosynthesis

Bron:D. Klapwijk

dissimilation

Day-climate (General definition):

A optimal day-climate is a perfect combination of:

• Temperature• Light• Humidity• CO2

Day-climate? (1)

Day-climate (2)

To optimize climate in greenhouse the grower should react on:

1.Outside weather conditions

2.Greenhouse properties & facilities

3.Crop properties (tomato)

Day-Climate (3)

Outside weather conditions

• Wind (speed and direction)

• Lightlevel (radiation)

• Temperature

• Rain

• Snow

• Cloudiness

Day-Climate (4)

Greenhouse properties & facilities

• height • light tranmission greenhouse roof (glass+construction)• heating capacity (boiler+pipes)• insulation (loss of heat and humidity)• position of heating-pipes• growing on a gutter• ventilation capacity• screens (% heat saving)• CO2 dosage-capacity (kg/ha/hr)

Day-Climate (5)

Crop properties (tomato)

• Stem density, distribution of stems

• Cultivar

• Plant-load

• Pepino-virus

Day-Climate (6)

• Optimizing greenhouse climate is complex because of many variables

• It’s difficult to give concrete (absolute) figurs (f.e. temperatures)

• Consider all mentioned figurs in this lecture as “indicative” and not as “absolute”

• The big point is how to interprete the figurs to your specific conditions

• Watch your crop. The plants are always telling the truth!!!

• Sunrise the crop must be heated up sufficient (17-19°C)• Sunrise (lowest outside temperatures!!)• Too cold heads in the morning (especially in combination with ventilation) is a major

cause of problems:

-Botrytis-Small fruitsize-Fruitskin problems (cracking, cold head warm roots)

Plant physiological process involved:

-stretching process of plantcells-evaporation process (transport of water,nutrients,assimilates)-condensation risk (physical process)

Day-climate(7) Morning

Morning

• A “bad” colour in the head is typical for cold heads

• Charactaristic is too short internodes and too thick stem

• Heating up the crop in the morning can be finetuned with sensors like:

-plant temperature meter ( T plant-air-temperature)

-irradiation sensor (measures heat irradation from the greenhouse up to the sky).

• A good start in the morning (at sunrise 17-19°C)• Followed by a gradual raise during the morning towards +/- minimum 18-maximum 26°C in the

afternoon. We call this a “peak”

Reasons of peak:• To stimulate evaporation (uptake of water and nutrients),especially when the lightlevels are

low.• Optimal photosynthesis is at 18-26°C• Release of pollen (& activity of bumblebees)

When above happens we call this an “active” climate, if not we call it a“death”climate

Especially a fast rise in the morning to a peak affects the shape of plant:

-fast rise to (high)peak=long internodes,thin stem-slow rise to (low) peak=short internodes, thick stem

Day-climate(8) Afternoonpeak

PN AN SR SS PN

peak12-17°C

17-19°C

18-26°C

12-17°C

Temperature strategy tomato

-At a low peak there is a higher risk of a “death” climate

-The right “peak” temperature depends on:

• Power of the heads (“slim” or “fat” )

• Required heating pipe temperature (see table)

• Lightintensity (175-250 Watt/m2 important traject)

• Air Humidity Deficit-Not active HD<3 (“death” climate)-Active HD 3-5-Very active HD > 5

Day-climate(9) Afternoonpeak

Peak T Pipe T Pipe T Pipe T Pipe T Pipe T18 0-45 death 55 mild 65 active 75 active+ 85 active++

19 0-40 50 60 70 80-8520 0-35 45 55 65 75-8021 0-30 40 50 60 70-7522 0-25 35 45 55 65-7023 0-25 30 40 50 60-6524 0-25 25 35 45 55-6025 0-25 25 30 40 50-5526 0-25 25 25 35 45-50

Rail pipe T, Peak T (heat) & classification Day-climate

1.Too much limitation heating pipes

2.Measures to keep lenghtgrowth limited (short internodes)

3.Too late reaction to changes in weather

4.Too fast reduction of minimum pipe temperature

4 major “day-climate” items resulting in problems

• Maximum pipe temperature-Sunrise heating setpoint MUST be reached.

• If not, pipe is relative hot when sun gets strong strong rise of temperature higher condensation Botrytis

• Repeatedly a too low temperature in the morningSHORT INTERNODESFAT HEADS

1.Too much limitation heating pipes

• Understandable reasons (height greenhouse, labor, energy)

• Relative low temperatures around sunrise (night/morning)

• To drastic means a bad growth fruitsize remains small too!!

• Especially dangerous in combination with ventilation

• Always relate ventilation stategy to outside air-temperature

• Sometimes too much efforts made to keep it cool cold headsbotrytis, fruitskin problems

2.Measures to keep lenghtgrowth limited (shorter internodes)

Connect settings on climate computer to outside weather conditions

With “standard” equipment:-T-outside -Lightlevel-Wind (speed & direction)-Rain

-Outside humidity -Irradiation sensor (measures heat irradiation from thegreenhouse up to the sky) cloudy or clear sky?

3.Too late reaction to changes in weather(1)

3.Too late reaction on changes in weather(2)

• Plant has “history” but no “memory”:

-Properties of crop are result of actions in past

-Improvement of growth strategy will direct result in improvement of growth, despite bad history

• “Average” figures:-do not give all required information-more important: what happens at specific moments-graphs give more info

2 main reasons to maintain minimum pipe temperature (rail system)

1.To create evaporation of plant (only at low lightlevels in winter)2.Mixing cold and warm air:

• Ventilation at outside T < 15°C cold air “falls” down in the crop

• This air should be mixed otherwise condensation

• To create air movement T-pipe should be 15-20°C > greenhouse airtemperature. “Feel” the climate sitting on rail under open window.

• Reduction of pipe temperature relate to lightlevels and outside air temperature (< 10, 11-15 and >15°C)

• On most climate computers no automatic connection to outside T!!!!!

4.Too fast reduction of minimum pipe temperature.

Creating air movement in greenhouse

Air movement required especially at basis of crop to prevent condensation risks.How?• With minimum pipe (T 35-45°C)

• Tubes under gutter

Basic version:-air tube under gutter-tube combined with electric fan-mixing air layers

Tube located under gutter

PN AN SR Peak SS PN

Outside T < 10 °C Minimum Pipe Strategy (rail)

25 35 45 45 25

-10 (175-250 Watt)

PN AN SR Peak SS PN

25 35 45 40 25

-5 (175-250 W)

Outside T 11-15 °C Minimum Pipe Strategy (rail)

PN AN SR Peak SS PN

20 35 45 4020

-5 -20 (150-200Watt)

Outside T >15 °C Minimum Pipe Strategy (rail)

• Use of “sugar” (energy, assimilates)

• Day & night

• Day: assimilation+dissimilation

• Depends on temperature

2 Dissimilation processes:

1.Existing plantcells use energy (f.e. transport)

2.Production of new cells (growth) requires energy

Dissimilation

Bron:D. Klapwijk

Dissimilation

dissimilation

Assimilation minus dissimilation=growth

Assimilation (day) > Dissimilation (day & night)

Surplus sugar

Stronger heads & trussesBigger tomatoes

Higher productionhighest netto fotosynthesis

Netto fotosynthesis

Bron:D. Klapwijk

dissimilationHigh netto fotosynthesis

Low netto fotosynthesis

In night only dissimilation

• Higher T-night=more (vegetative) growth?

Higher night T=more new cells but less “sugars” left for generativeparts weak truss smaller tomatoeslower production.

• Weak trusses at start? High risk of too vegetative plant (unbalanced crop) BIG LEAVES & SMALL TOMATOES

• Best method to create balanced (generative) crop is to prevent weak trusses.

• How? GH temperatures must be in balance with:– Cropstage (nr. flowering truss, heads/m2)– (Natural) light levels

Night-climate (1)

• Most problems with growth are because of a bad day-climate

• Don’t “repair” a bad growth because a bad “day climate” by raising the night T

• First optimize day-climate

• General thought: (More) equal temperature regime=more growth??? (lower day T-higher night T)

• There are some some exceptions to this “rule”:

Night-climate (2)

Equal Temperature D/N=Vegetative?

Also observed in practice:

• At (extreme) cold nights a high night T high pipe T less humidity leafs get smaller.

• A lower GH-T during day can also result in a “death” climate plant does not evaporate no transport of water, nutrients and assimilates =no growth at all!!!

Night-climate (3)

Balance between crop parameters, light andlightlevels

• In young crops relative high night-T to create leafs as fast as possible.

Truss must stay strong!!!

• At low light-levels and bigger plant lower 24-hr.averages mainly by adjusting night-temperature.

24-hr average T-regulation 1

24-hr average T-regulation 2

Most important factors involved• Plantsize (nr. flowering truss)

Bigger plants have higher dissimilation losses lower night-temperatures• Daily lightsum

At lower lightlevels lower assimilation prevent dissimilation > assimilation by lower night-temperatures

• Stem-density (and distribution)At higher stemdensity less light per headless assimilation prevent dissimilation>assimilation by lower night-temperatures

• Pepino-virusConsider the virus as a parasite that takes assimilates lower night-temperatures to reduce dissimilation losses.

• Observation trussWhen truss is too weak lower night-temperature. When truss is too strong raise day-temperature

• Other factors(greenhouse, lighttransmission etc.)

24-Hr Temperature regulation related to plant-size and daily lightsum

Truss* 100 200 300 400 500 1000 Joule/cm2/day

1 17,3 17,5 17,8 18,2 18,5 20,1 °C 24-Hr

2 17,0 17,3 17,6 17,9 18,2 19,9 °C 24-Hr

3 16,8 17,0 17,3 17,7 18,0 19,6 °C 24-Hr

4 16,5 16,8 17,1 17,4 17,7 19,4 °C 24-Hr

5 16,3 16,5 16,8 17,2 17,5 19,1 °C 24-Hr

6 16,0 16,3 16,6 16,9 17,2 18,9 °C 24-Hr

7 15,8 16,0 16,3 16,7 17,0 18,6 °C 24-Hr

8 15,5 15,8 16,1 16,4 16,7 18,4 °C 24-Hr

*Flowering Truss

24-hr average T-regulation 3, table

T-heating pipes important factor!!!!!!!!!!!!!!

• 24-Hr Temperature regulation related to plant-size and daily lightsum.

• A good guideline, but every situation is different. Keep watching the plant, especially head+truss

• Too low 24 Hr-temperatures may create too strong trusses and too coarse flowers. Mainly a danger in young crops with low fruitload.(Truss 1-5 flowering). Raise 24 Hr by:

1.First optimize day-temperature (higher)2.Crop must be heated at sunrise (f.e 171819°C)3.Higher night by shorter PN and longer AN

24-hr average T-regulation 4

24-hr average T-regulation 5

Weak truss?

Step 1.Lower T-night (pre-night)Step 2. (less common) Lower T-day (but avoid “death” climate

pollen must release)

Too strong truss?

Step 1.Higher T-day (also T at sunrise)Step 2. (less common) Higher T-night (shorter pre-night)

Pre-Night & After-Night (PN, AN)• Night-temperature used to correct 24 Hr.T• Reason PN and AN mainly technical:

-PN: cool down with cold pipe and screen open (closed if very cold)-AN: warm up with hot pipe and closed screen

• In PN pipe is cold , relative humidity gets (too) high. • As long GH temperature goes down there will no be condensation (maximum length

PN!!)

• Rough practical guideline: maximum 4-6 hours with “cold” pipes=maximum lenght pre-night (2 hours before- 4 hours after sunset

• After stabilisation temperature, greenhouse must be heated up with maximum 1°C per hour (faster=higher risk of condensation)

24-hr average T-regulation 6

“Speed”• Flower-Harvest approximately 6-10 weeks

• Lightlevel/plantload determines 24 Hr-average. 24 Hr-average determines speed.

• Important for speed is optimal day-climateCold heads and a death climate cannot be compensated by a warmer night

• Higher 24 Hr-averages with relative warm nights will result in:

1.slightly faster from flower to harvest (less then a week)2.Higher risk of weak heads and trusses (quality problems in hot summers)3.Smaller fruits (but kg’s not compensated by more trusses and fruits)4.Higher risk of unbalanced growth (too vegetative) because of weak trusses & small fruits

Speed of growth

• A good growth is mainly a matter of day-climate management.• Best results (quality and production) are obtained at growers who:

-have excellent feeling for crop and day-climate-know how to translate this feeling to settings on computer-have crop heated up sufficient at sunrise-have a relative cool night-temperature-look more at the crop instead of the figurs/numbers-react keen on changing outside weather conditions

-have a crop planning that is in balance with (natural)light conditions Green scheduler crop planningmodel

Conclusion

Questions?

Thanks for your attention!

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