A simple model for predicting transpiration of greenhouse cucumber

Summary A simple model is presented that predicts transpiration of a greenhouse cucumber crop. Leaf area development, which is important for transpiration prediction at least until complete soil cover, is calculated from a simple dry matter production derived model. This model calculates total dry matter production from intercepted radiation and light use efficiency, leaf area growth is determined from the fraction of dry matter allocated to the leaves and the specific leaf area. The calculation of crop transpiration itself is based on the Penman-Monteith approach. For parametrisation and validation of the model data of two previously published experiments with greenhouse cucumber at different locations (Wageningen and Hannover) were used. The determination of the aerodynamic and the canopy resistance of the Penman-Monteith equation was done by adjusting these parameters with respect to experimental data. Applied to independent data the model was able to predict leaf area development until complete soil cover and daily water consumption of cucumber. Compared with results of a multiple linear regression analysis of daily water use dependent on radiation and vapour pressure deficits, the presented model showed its superior predictive value especially during the young plant period of the crop when soil cover was incomplete.