HORTISIM: A MODEL FOR GREENHOUSE CROPS AND GREENHOUSE CLIMATE

A combined model for crop production and climate in greenhouses, HORTISIM, was developed. Existing models, developed by several research groups, of various aspects of crop growth and greenhouse climate have been integrated. HORTISIM contains 7 submodels (Weather, Greenhouse Climate, Soil, Crop, Greenhouse Manager, Soil Manager and Crop Manager) plus a simulation process manager (the “Engine”). Climate conditions inside the greenhouse can be calculated from outdoor weather. The use of energy, CO₂ and water can be quantified. Crop photosynthesis, dry matter production, dry matter partitioning and individual fruit growth in fruit vegetable crops can be simulated.

Validation of the energy balance of a Venlo-type glasshouse with a tomato crop in The Netherlands showed that difference between simulated and measured instantaneous air temperature was mostly less than 2°C (average deviation was 0.53°C).

Crop transpiration and dry matter production have been validated for Dutch and Israeli conditions. Daytime crop transpiration was simulated reasonably well, being overestimated on average by 8% for tomato in The Netherlands and 1% for sweet pepper in Israel. The Israeli results were quite sensitive to the choice of using mid-canopy or above-canopy temperature and VPD measurements as model input. In many situations simulated dry matter production agreed well with experimental data, although dry matter production of sweet pepper in Israeli greenhouses was overestimated by 28%. Dry matter partitioning in sweet pepper was simulated rather well when simulation was based on organ sink strengths, with dates of anthesis and harvest of non-aborted fruits as model input.