Alternative sytem of growing tomatoes

The Green Q way.

10 February 2010André Kool, crop consultant, Green Q

Alternative sytem of growing tomatoes

Starting points• Double screen

• Low density start 1.67-1.90 heads / m2

• Single grafted plant (1 on 1)

• Doubled in spring f.e. 1.673.33

• Stemdensity and plantload better in balance with natural light

Content

Growing aspects under double screen– Advantage– Disadvantages– Points of extra attention

• Generative crop steering• Plant density• Greenhouse air humidity

– Economics

Technical aspects under double screen

Use of heating pipes (rail pipes and growth pipes)

Crop planning

1. Growing aspects

Goals?

• Energy saving?

• Fast early production to get high prices?

• Stronger crop, less sensitive for diseases (virus…)?

Installation

• Movable screen in top

• Fixed AC-foil below on seperate system of wires above crop wire: condensation drop will be between rows

• Stable air layer between screens gives extra isolation

Advantages

• Better start climate for young plant– Higher humidity at start.– Lower pipe temperatures.– When opening movable screen no cold air falling on crop

especially nice in case of pepino virus. – Less rduction of light at closed plastic foil compare to closed

movable screen. – Easier growing at higher temperature levels because of higher

isolation of greenhouse (especially with low density start) – Energy saving at both screens closed: 50-55%– Only movable screen =40%– Only fixed foil =20%

Disadvantages

• Horizontal temperature differences– Because of rolling down of cold air above foil and perforation

foil cold air can fall down on some spotscompartments between screens can be made.

• Light reduction foil 10%

• Too late removal of foil is higher risk on diseases

Points of extra attention

• Keep more generative growing stategy (climate)

– Plant temperature at day time is lower because of less direct light

– Plant temperature at night is higher because of less radiation to outside.

– Big DIF steering required (warm day, cool night) – In the afternoon the greenhouse climate should make the

plant evaporate and the plant color should be “dark” at the end of the afternoon.

– Heating with a growth pipe is a good help….

Points of extra attention

• Low density start (f.e. 1.67 heads / m2 versus 2.5 heads / m2 )

– Less crop under foil will create less problems with humidity

– Low density and low plantload more light per head higher “growth speed” possiblehigher 24-hr-average

• Less problems with humidity• Better utilisation double screen• Better growing conditions in case of pepino-virus

Points of extra attention

Development crop load at 2 start densities

0

30

60

90

120

150

1 2 3 4 5 6 7 8 9 10 11 12

cro

p l

oad

(fr

/m2)

0

0,2

0,4

0,6

0,8

1

spee

d t

russ

(tr

uss

/wee

k)

crop load 50 cm crop load 75 cm speed truss 50 cm speed truss 75 cm

Points of extra attention…..humidity

• Maximum tolerance of humidity levels under screen?– At cooling down greenhouse air less risk on condensation.

– At warming up greenhouse air high risk of condensation.– HD pre-night > 1.0-1.5

– HD after-night >1.5-2.0

– HD morning>2.0-2.5

– HD day >3.0 (preferably 4.0-6.0 in afternoon)

Points of extra attention…..humidity

– Humidity control by:1.Ventilation above plastic foil (outside no frost)2.Air-movement by minimum (growth) pipe

– Warm air can contain more water lower humidity

Removal of plastic foil– When you humidity control becomes a problem– A movable second screen would even be better………

Economics

Costs*• Materials plastic foil screen € 0.15 per m²• Labour (experienced) € 0.05 per m²• Total € 0.20 per m²*Dutch price levels

Savings• Depending on outside circumstances• 5-20% extra in respectively mild and cold winter

2. Technical aspects

• Energy saving

• Type en perforation

• Ventilation above plastic foil

• Cooling down in pre-night

• Screen policy

• Measuring box above screen

• Heating with what pipes?

Energy saving

• Movable screen (LS) f.e. 40% (climate computer!!)

• Fixed plastic foil 10-15-20-25 % ? Check pipe-and greenhouse temperature in graphs

• “Too slow” reacting pipe, delayed GH –temperature higher energy saving % on computer

• “Too aggressive” reacting pipe, overreaction of GH-temperature higher energy saving % on computer

• In general: too big fluctuations in pipe-and greenhouse temperature can be indication of wrong setpoints for energy saving %

• Not good for climate and energy consumption.

Energy consumption at various scenario’s

18 ºC Greenhouse temperature Modern well isolated greenhouse, no windspeed, no radiation, no precipitation10 51 mm pipes per 8 m (1,60 meter row distance)Figurs are pipe-temperatures with (….) gas consumption in m3/ha

T-outside no screen Plastic foil Movable Plastic+movable

-10 74 (188) 66 (152) 58 (120) 50 (110)

-5 66 (152) 58 (123) 50 (91) 46 (76)

0 58 (123) 51 (95) 45 (73) 41 (59)

5 49 (88) 44 (69) 38 (52) 35 (42)

10 40 (55) 35 (42) 32 (33) 30 (26)

Type and perforation

• AC, otherwise to dark and dripping

• No 5 x 5 cm too much cold air falling on lowest points

• Standard 10 x 10

• 1-2….poles near sidewalls: 40 x 40

• With fans blow from warm spots to cold spots

• At highest spot (=warmest spot ) make plastic movable (at middle pathway).

Ventilation above plastic screen

With mild weather and / or very sunny weather :

Ventilation above fixed plastic screen because of:

• Rising greenhouse temperature

• Too high greenhouse air humidity

Ventilation above plastic screen

Points of special interest:

• Ventilation setpoint close to heating setpoint (dead zone 0°C)

• Reduction ventilation setpoint at high greenhouse humidity

• Quick ventilation at windside (no delay at 0 m/s windspeed)

• Maximum window position limited at high windspeed to prevent damage to plastic screen.

• Sunny and frostVentilation should be possiblefrostprotection setpoint based on radiation

• After removal plastic foil don’t forget to put back “normal” setpoints

Cooling down to pre-night

• Difficult at mild weather (>10°C).

• With ventilation setpoint follow parallel heating setpoint.

• With “cold” pipes. 25°C is too warm. Pumps out.

• As long GH temperature moves downno condensation.

• If necessary ventilation also at the windside.

Screen policy (movable screen)

There is a fixed plastic foil so movable screen….

Earlier open, closed later (only closed with frost)

Smaller dead bands and delays, bigger steps.

Easy gapping based on temperature or humidity

Ventilation setpoint close to heating setpoint

After removal plastic foil don’t forget to put back “normal” screen setpoints

Measuring box above screen

• Measures temperature rise above screen

• Most direct signal to open screen

• Measuring box above screen to open ánd close movable screen above fixed foil

• In case of only 1 (movable) screen : measuring box only help to open screen

Heating with what pipes?

• (Double) screen means colder pipes

• Less radiation and less air movement

• Higher risk on a “dead” climate

• Heat closer to the plant with growth pipe (=primary heating system)

• Thinner pipes = hotter pipes locally more radiation and air movement

• Heat at the point where you need the heat: close to the plant…..

Heating system

Rail pipe

Growing Pipes (spiral)

Heating with what pipes?

• Thinner pipe Relative big surface compared to water content Relative high lost of heat on the lenght Bigger delta-T (Difference supply-return water temperature)

• Because of this thinner pipe, preferably a spiral (equal discharge of heat over the lenght of the crop row)

• Single growth pipe? Preferably a thicker pipe (less delta-T)

Heating with what pipes?

• Primary heating with growth pipe results in generatieve, weak and thin plant?

Not necessarily.Take care off:

• When heating primarily with growth pipe heating setpoint slightly lower than “conventional” (1-2°C) will also save energy

• Reduction of maximum growth pipe temperature at low humidity

• Think more in plant temperature……..

• Keep LOOKING at plant

Heating with what pipes?

• There is only sufficient air movement if pipe temperature is minimal 20°C higher than surrounding greenhouse air temperature..

Heating with what pipes?

• Create air movement there where it’s required:

• Close to the crop (between)

• Position growth pipe (under of above growth gutter)

• Influence radiation on truss / fruits

• Locally more radiation and air movement with a smaller but hotter pipe

Thinner rail-pipe (5145 mm= 2-3°C higher pipe temperature)

Growth pipe (spiral) versus rail pipe (4528 mm = 10°C higher pipe temperature ) (total consumption energy equal)

Heating with what pipes?

• At lower heat demand (double screen) it’s more inportant to bring heat and air movement closer to the plant

• Heating closer to the plant (primary with growth pipe) result in more air movement close to the plant and a warmer plant

• Because of this the heating setpoint can be chosen a little bit lower

• Generally this way of heating results in a more efficient use of energy

Crop planning

“Live” demonstation of Green Scheduler

crop planning program

Questions?

Thanks for your attention!

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