Wageningen UR was commissioned by Kas als Energiebron (Greenhouse as Energy Source) to carry out research into various options for more efficient use of CO2 in greenhouses. In this particular research, specific attention was paid to the hitherto rather unexposed CO2 problems in chrysanthemum and sweet pepper. Thus, knowledge was built up on the role of CO2 in growth, product quality and on the efficiency of CO2 deployment together with the sector and thanks to study of previous research for those crops. With available data, growth models for chrysanthemum and sweet pepper were calibrated to predict promising strategies for efficient CO2 use.
For chrysanthemum, the recommendations (DOs) and unwise things (DON'Ts) are as follows:
DO:
- CO₂ concentration of 800 ppm is usually sufficient for plant, at very high light 1000 ppm
- At high window position (>20%)(so high ventilation rate), give much less CO2, a guideline is 60 kg ha-1 hour-1 , this is the max crop uptake
- Lower doses in long-day and 1st week of short-day make sense
- Distribute CO2 evenly over the day, but not if window is (far) open
- In the light period, start half an hour later and stop earlier
- Light-dependent dosing capacity, but keep to 800 ppm setpoint
- Fogging: good for CO2 utilisation by plants and less need for airing
DON'T:
- Dosing in the long-day phase: enough comes out of residual greenhouse
- High peaks in CO2 concentration: plant cannot do anything with it
- Trying to bring in outside air CO2 when dosing simultaneously: leads to more CO2 loss
- Higher concentrations than 800 ppm on dark days (despite lighting): not very effective, and plant becomes lazy in CO2 uptake
TIP:
- Calculating with a CO2 optimisation tool the CO2 strategy decisions can support in practice. Consider the following tools: (1) OCAP Optimal, (2) CO2 optimiser from Ridder
For pepper, the recommendations (DOs) and unwise things (DON'Ts) are as follows:
DOs:
- More effective CO2 dosing (e.g. in morning, or only when windows are <20% open, capacity lower in summer, light-dependent dosing)
- Not too high set point: above 800 ppm the effect on growth is nil
- Short periods limiting dosing to outdoor CO2 value can save a lot of CO2 without much effect on harvest, e.g. at weekends or in periods with a lot of ventilation
- There will always be some reduced harvest though: weigh up against CO2 costs
DON'T:
- Trying to bring outdoor CO2 in via draught and dosing CO2 at the same time
- High peaks in CO2 concentration: plant cannot do anything with it
- Dosing capacities of 200 kg in summer period give a lot of CO2 loss and relatively few extra kilos of production
TIP:
- Calculating with a CO2 optimisation tool the CO2 strategy decisions can support in practice. Consider the following tools: (1) OCAP Optimal, (2) CO2 optimiser from Ridder.
The whole report can be found here.