A DYNAMIC MODEL TO ESTIMATE IN–CANOPY AND LEAF–SURFACE MICROCLIMATE OF GREENHOUSE CUCUMBER CROPS

摘要

A dynamic one-dimensional model, PSCLIMATE, was developed to simulate microclimate on and around leaf surfaces for greenhouse cucumbers. Based on an energy balance of plant leaves and heat and mass transfer among air strata and leaves, the model predicts climate profiles within a plant canopy and the microclimate within a leaf surface boundary layer. The simulated in-canopy and leaf-surface climate profiles can be used to improve the prediction of pest outbreaks and their control for greenhouse cucumbers. Validation of the model with data collected from a glass greenhouse indicated that air temperature (T _a ) and relative humidity (RH _a ) within the canopy were accurately predicted (RMSDs 0.6°C and 2.9% at night and RMSDs 0.2°C and 3.9% in the daytime). Leaf surface temperature (T _l ) was predicted with an RMSD 1.3°C for shaded leaves and 2.7°C for sunlit leaves. Leaf wetness incidence, as measured by a leaf wetness sensor, was predicted correctly for a sunlit leaf but not for a shaded leaf. Predicted vapor pressure deficit within the leaf surface boundary layer provides information that cannot be measured directly by sensors. This model can be used for other crop canopies or greenhouse structures once the specific characteristics of the greenhouse structure and the plant canopy are defined. Further improvements to the model are discussed