Study on Changes of Microclimate in Greenhouse of Pleurotus nebrodensis in Jizhou, Tianjin

Based on the air temperature (1.0 m and 1.5 m) every 10 minutes, ground temperature (0 cm, 10 cm and 20 cm) and air relative humidity (1.5 m) from the stations in the greenhouse, and the air temperature (1.5 m) every 10 minutes and air relative humidity (1.5 m) from the regional stations in Chutouling Town, Jizhou district of Tianjin from April 2019 to November 2020, the changes of the microclimate in the greenhouse of Pleurotus nebrodensis were studied. The results explained that 1) the heat preservation effect of the greenhouse was the best in spring, the effective accumulative temperature and active accumulated temperature in the greenhouse had increased by 203.7°C and 233.7°C, respectively, compared with that outside the greenhouse. In the sunny or cloudy days of summer, the range of temperature difference (TD) between inside and outside the greenhouse was wider, more than 90% of the TD ranged from -6.0°C to 2.9°C;2) the minimum temperature occurred later because of heat preservation effect of the greenhouse, the delay time can reach about 30 minutes in spring, it was about 20 minutes in summer and autumn, and 10 minutes in winter, however, the maximum temperature appeared earlier, it occurred 50 minutes ahead of time in spring, and it has been advanced by 20 minutes in summer and 10 minutes in autumn and winter;3) the greenhouse mainly played a role of increasing humidity, the humidity in the greenhouse basically was larger than that outside the greenhouse, except the periods of 03:10-07:20 in spring, 0:00-08:50 and 23:10-23:50 in winter;4) the temperature in the greenhouse significantly positively correlated with the temperature outside the greenhouse, the stronger correlation also appeared between the ground temperature (at the depth of 0 cm and 10 cm) in the greenhouse and the temperature inside and outside the greenhouse, however, there was a weak correlation between the ground temperature (20 cm) and the temperature inside and outside the greenhouse, this implies that the change of temperature had less impact on the ground temperature at deeper soil layers. This paper is of significance in identifying the microclimate in the Pleurotus nebrodensis greenhouse.

Irrigation decision model for tomato seedlings based on optimal photosynthetic rate

Soil moisture is a major environmental factor that influences tomato growth and development.Suitable soil moisture not only increases tomato production but also saves irrigation water.In this study,an irrigation decision model was developed,which called soil moisture regulation model,for optimizing growth of tomato seedlings while saving water.The data used for modeling were collected from a multi-gradient nested experiment,in which temperature,photosynthetic photon flux density(PPFD),carbon dioxide(CO2)concentration and soil moisture were variables and the corresponding photosynthetic rate was measured.Subsequently,a prediction model of tomato photosynthetic rate was constructed using support vector regression(SVR)algorithm.With photosynthetic rate prediction model as fitness function,genetic algorithm(GA)was used to find the optimal soil moisture under each combination of the above environmental factors.Finally,back propagation neural network(BPNN)algorithm was used to establish a decision model of tomato irrigation,which could provide the optimal soil moisture under current environment.For the soil moisture regulation model constructed here,the coefficient of determination was 0.9738,the mean square error of the test set was 1.51×10-5,the slope of the verified straight line was 0.9752,and the intercept was 0.00916.This model demonstrated high precision,which thereby provides a theoretical basis for accurate irrigation control in the greenhouse facility environment.