Development of a microclimate model for prediction of temperatures inside a naturally ventilated greenhouse under cucumber crop in soilless media

The microclimate inside a protected structure is affected mainly by physical processes involving heat and mass transfer between plants, air, growing media and the plastic cover. The microclimate within plant community directly affects the plant metabolic activities and therefore the production. Thus, it becomes imperative to monitor and maintain the microclimatic parameters to desired range for optimal plant growth and development. A microclimatic model of a naturally ventilated greenhouse under cucumber crop in soilless media was developed by considering the heat or mass transport processes (convection, radiation, transpiration and natural ventilation) and solved in Simulink MATLAB. The model performance was evaluated statistically through a comparison between predicted and observed data. The averaged absolute percent error for temperature of air, plant, growing media and was computed to be 8.9%, 7.6%, 8.0% and 10.6% respectively. The coefficient of determination (r2), root mean square error (RMSE) and model efficiency (ηeff) were obtained to be 0.96, 0.11 °C and 94.7% respectively. The statistical comparisons indicated that the developed microclimate model was sufficiently accurate to predict the temperature at air, plant (leaf), growing media and greenhouse cover under cropped conditions inside a naturally ventilated greenhouse. However, some model coefficients may require adjustments with respect to change in crop type and greenhouse conditions. The model output would be helpful in monitoring and offering optimal plant growth conditions which in turn can help in irrigation and fertigation management of the crop grown.