A procedure for optimizing carbon dioxide enrichment of a glasshouse tomato crop

The procedure consists of two parts. A Gompertz model for the kinetics of fruit growth is used predict the time distribution of photosynthate subsequent harvests. This is combined with predictions of future market prices to compute estimates, one for each day from first anthesis, of a factor to convert CO2 assimilate to expected financial value, based on the worth anticipated from partitioning to fruit. A model of the climate and the crop regime is used to predict temperatures and hence allow for the temperature dependence of fruit growth. The conversion estimates are revised to include the deferred benefit given by additional photosynthesis through increasing early vegetative growth, and hence subsequent photosynthesis and yield. This revision also extends the set of conversion factors to include any period before first anthesis. Given the current environmental variables and conversion factor for that day, a real-time system can use a crop photosynthesis model to predict the cash benefit for any CO2 concentration. The cost of maintaining a concentration can be obtained from a prediction of the ventilation air exchange rate and the unit price of CO2. The CO2 set-point is evaluated as the concentration that maximizes the net profit rate. (C) 1996 Silsoe Research Institute