Energy saving in greenhouses based on

crop physiology

Prof Dr Leo Marcelis

Chair Horticulture & Product Physiology

Wageningen University, Netherlands. Leo.Marcelis@wur.nl

In greenhouses:

An enormous yield increase

30 years:

Yield doubled in tomato

Where is the limit?

Doubling possible!

Energy consumption dropped

0

20

40

60

80

100

1980 1990 2000 2010

Yie

ld (

kg

m⁻² y

r⁻¹ )

Year

Tomato +113%

Sweet pepper +90%

Cucumber +35%

In 30 years yield doubled.

Which part due to breeding?

2

4

6

8

10

To

mat

o h

arv

est

(kg

m-2

)

1940 1960 1980 2000

year of cultivar release Higashide & Heuvelink, 2009

0.9% per year (27% in 30 years)

Genetic improvement tomato due to

- higher photosynthesis

- lower light extinction

Yield = Total biomass production Assimilate partitioning

( = Harvest Index)

Light use efficiency

Light absorption

Light extinction Leaf photosynthesis

Leaf Area Index

Concept for energy saving

Next generation cultivation (‘The new way of growing’)

Ambition

● 40-50% energy saving

● Same yield and quality

● Modular set-up

Next Generation cultivation

Insulation

Follow nature

De-humidify by controlled inlet air

Humidification

Heat harvest= cooling

Greenhouse coverings

Maximize light transmission

Diffuse light

Low energy loss

Next Generation cultivation

Insulation

Follow nature

De-humidify by controlled inlet air

Humidification

Heat harvest= cooling (aquifer)

Temperature control

Strong dependence radiation

● 1 ˚C lower base heating temperature

● 2,5 ˚C stronger light effect

Larger difference heating and ventilation setpoint

Temperature integration (3d, 5˚C d) 1m3

3,2 m3

saving

Next Generation cultivation

Insulation

Follow nature

De-humidify by controlled inlet air

Humidification

Heat harvest= cooling (aquifer)

Inlet outside air for dehumidification

droge warme lucht

Luchtbehandelingskast (10 per ha)

Aanzuigbuis kaslucht

Buitenlucht

aanzuiging

Air treatment unit

Dry warm air

Sucking outside air

More homogenous air humidity

Therefore higher humidity is possible

Screens kan be kept closed longer

Window opening in greenhouses

Opening ventilation windows for cooling and dehumidification

loss of energy and CO2 and water vapour

Beneficial to keep them more closed

From macroclimate to microclimate

(from greenhouse climate to phylloclimate)

3-way interaction:

climate – plant architecture - disease

Vertical temperature gradients

Top

Middle

Low

Floor

Hour of the day

Cooling from below

Air

tem

peratu

re (

˚C

)

Cooling from below: strong temperature gradient

No effect on plant development and growth when temperature at top is maintained

Slightly larger fruit size

From: Qian et al. J. Hort. Sci (2015)

Plant temperature: non uniform

From: Savvides, van Ieperen, Dieleman, Marcelis,

Plant Cell Environm (2013)

Plant temperature: non uniform

From: Savvides, van Ieperen, Dieleman, Marcelis,

Plant Cell Environm (2013)

Meristem temperature & the aerial

environment

-3

-1

1

3

45 60 75 90

Tm

eris

tem

– T

air (o

C)

RH (%)

Day

45 60 75 90

RH (%)

Night Cucumber Tomato

Relative Humidity (%) Relative Humidity (%)

From: Savvides, van Ieperen, Dieleman, Marcelis,

Plant Cell Environm (2013)

Leaf initiation rate & bud temperature

Tbud/Tplant

Savvides, et al. Planta (2016)

Plant phenotype

in relation to

apex temperature 30cm

26oC

22oC

18oC

18oC

18oC

18oC

Apical bud temperature

Air temperature (ºC) ``

Savvides, van Ieperen, Dieleman, Marcelis,

Plant Cell Environm (2017)

What is an optimal leaf area?

0

1

2

3

4

5

6

7

8

9

0 100 200 300 400

Tijd (dagen na planten)

LA

I (m

2 p

er

m2)

Time (days after planting

Sweet pepper

What is an optimal leaf area?

0

0.2

0.4

0.6

0.8

1

0 2 4 6 8

Ligh

t In

terc

ep

tio

n (%

)

Leaf Area Index (m2 m-2)

What is the contribution of different leaf layers?

(layer 1 = bottom, layer 5 = top; LAI >6 )

Lower layer: photosynthesis stronger reduced

than transpiration

Crop transpiration

0

50

100

150

200

17-6 16-8 15-10

Date

mm

ol H

2O

m-2

leaf day

-1

5

4

3

2

1

Crop net photosynthesis

-100

100

300

500

700

900

17-6 16-8 15-10

Date

mm

ol C

O2 m

-2le

af day-1

5

4

3

2

1

What is optimal leaf area?

Most of the light captured at LAI=3-4

● Further increase in LAI

● not much more photosynthesis

● Transpiration keeps increasing

● High air humidity, in particular inside canopy

● Increased maintenance respiration?

● Formation of leaves costs assimilates

Removal of young leaves Fraction of assimilates to fruits: 7 7 _____________ = 0.7 __________ = 0.77 (7+1+1+1) (7+1+1)

Yellow numbers inside leaves and truss = ‘sink strength’

10%

10%

10%

1

1

1

7 70%

11%

11%

1

1

7 77%

Simulated cumulative fruit and total dry weight, fraction partitioned to the fruits and average LAI

LAI was not affected as old leaves were removed every time LAI>3 consequently total plant dry weight (vegetative + generative) was not affected

Treatment = removal of young leaves

___________________________________________________ Treatment DWfruit Fraction (leaf removal) (kg m-2) fruit/total ___________________________________________________ Control 2.92 0.69 1 out of 6 3.01 0.71 1 out of 3 3.11 0.74 ___________________________________________________

Leaf picking strawberry

Treatment LAI (m2 m

-2) Total Biomass (g DM/plant)

Fruit Yield (g/plant)

Fraction partitioned to fruits

Reference 3-4 81 a 430 a 0.50 a

Young leaves removed 2.5 73 a 465 b 0.59 b

Old leaves removed 2.5 436 a

From: Venner &

Marcelis, unpublished

Conclusions

Next generation cultivation

● Insulation, flexible temperature, dehumidify

From macro to micro climate

Leaf formation: often too much

28

Thank you for

your attention !

Course on lighting:

7- 9 Feb 2018

12-14 Feb 2018

Student Challenge

“Design the Ultimate

Urban Greenhouse”

WWW.HPP.WUR.NL