Greenhouse crop transpiration simulation from external climate conditions

A new and simple greenhouse crop transpiration model enabling predictions from outdoor conditions is presented and the parameters involved are discussed with respect to different types of greenhouse-crop systems. This transpiration model was validated against experimental data measured in a soil-less tomato crop cultivation in Avignon in summer conditions, when the greenhouse is open, and early spring climatic conditions, when the greenhouse is kept closed and the inside air strongly confined. The evapo-condensation phenomena on the greenhouse cover, particularly important when the greenhouse is closed, are not considered in the water vapour balance. Model estimation improved from spring to summer and comparisons with previous transpiration models have shown that considering outside climate instead of inside climate as a boundary condition implied a deterioration of transpiration model performances especially when greenhouse air is confined. This deterioration is primarily due to simplifications introduced during the model derivation and model performances were satisfactory when the greenhouse air was closely coupled to outdoor conditions. (C)2000 Elsevier Science B.V. All rights reserved.