Study On Microclimate Characteristics And Influencing Factors Of Crop Canopy In Solar Greenhouse

Greenhouse microclimate conditions directly affect crop growth,and the same physiological activities as transpiration and respiration of crop canopy and porous media characteristics of crops in turn have an impact on greenhouse microclimate.Taking the solar greenhouse planting celery crops in Hohhot as the research object,the environmental factors such as temperature,humidity and carbon dioxide concentration in the greenhouse were tested.The temperature and humidity in the crop canopy were measured by the way of dense sensor placement,and the water-heat coupling relationship between the environmental factors in the greenhouse and the crop-air was studied.Using computational fluid dynamics software,steady-state numerical simulation of temperature and humidity environment in greenhouse with or without crops and in different growing periods of crops was carried out.The distribution of temperature and humidity between crops and air was analyzed,and the differences of temperature and humidity in Greenhouse in different growing periods were compared.In view of the variation of temperature and humidity in different positions of crop canopy in solar greenhouse and the interaction with environment,Elman neural network was used to predict temperature and humidity in different positions of crop canopy using some data from non-crop areas.The results show that:(1)During the daytime,the temperature and humidity of celery canopy increased and decreased along the vertical direction due to different degrees of solar radiation.at night,the characteristics of porous media and physiological activities of crops affected the temperature and humidity of themselves and the air above.(2)At night,carbon dioxide gas tends to accumulate near the overburden.The variation of indoor carbon dioxide is related to greenhouse ventilation,solar radiation and crop area.(3)The simulation results show that the lowest temperature and the highest humidity in the greenhouse occur at the bottom of the crop canopy in daytime and near the outer soil mulch in the greenhouse at night.(4)Crop areas have an impact on greenhouse microclimate,and higher overall crop temperature varies greatly with higher relative humidity.(5)The Elman neural network trained with 8-day measured data can predict the temperature and humidity data in crop canopy through some data in non-crop areas.Compared with the measured data,the root mean square difference of the predicted values in one week is less than 1.5.This study is of great significance in guiding greenhouse crop cultivation and environmental control.