Irrigation Decision Support System For Eggplant Based On Evapotranspiration Model In Greenhouse

The key to realize precision agriculture is the combination of agricultural model and information technology.At present,because of lack of scientific guidance for irrigation decision,facility vegetable has the problems of large irrigation volume,serious water leakage.As a result,the utilization rate of water resources is low,and the supply and demand of eggplant for water can not reach an effective fit,final impacting the normal growth and development of eggplant and the formation of yield.Based on meteorological and crop growth data,the relationship between eggplant leaf area index and crop coefficient was analyzed by modified Penman-Monteith model(hereinafter referred to as P-M model)without water deficit,and a crop coefficient model was constructed.The modified Logistic equation was used to simulate the leaf area index.Relative effective accumulated temperature(the ratio of daily effective accumulated temperature to maximum effective accumulated temperature)was taken as independent variable,and relative leaf area index(the ratio of daily leaf area index to maximum leaf area index)was the most dependent variable.Combining the measured leaf area index with the corresponding effective accumulated temperature,the goal of simulating daily leaf area index is achieved.The background function is implemented in Java,and the interface is constructed in the front end with the Wechat programming language to form the eggplant irrigation decision support system.The results of this study are as follows:(1)Based on the modified P-M model,a model of eggplant crop coefficient was constructed.By modifying of P-M model,the reference crop evapotranspiration ET0 suitable for small greenhouse environment was calculated.The relationship between crop coefficient Kc and LAI was further analyzed,and a model of crop coefficient was constructed.The data showed that K_c had a significant linear relationship with LAI(P<0.01,R~2=0.86),indicating that the value of K_c could be determined by LAI.(2)To simulate the change characteristics of LAI of eggplant dynamically,and then realize the dynamic change of Kc.In this paper,relative effective accumulated temperature and relative leaf area index are used as input variables,and LAI growth model is constructed by combining measured LAI with relative effective accumulated temperature.By modifying the Logistic equation,the daily LAI is simulated.The results show that the revised Logistic equation has high simulation accuracy,R~2 reaches 0.98,and the relative error is 10.63%.It can accurately simulate the change of LAI.(3)Through the combination of crop coefficient sub-model,meteorological factor sub-model and leaf area index logistic model,a simulated daily evapotranspiration estimation model is formed.The results show that the RMSE of the model is 0.50mm/d and the relative error RE is 18.50%.(4)Development and design of decision support system for eggplant irrigation.The system provides functions of irrigation message reminder,data download,user registration,user location,customer service message,and provides users with practical and available services.User registration can upload the coordinate information of the shed to the server,the function of information positioning,and provide relevant interfaces.User registration can upload the coordinate information of the shed to the server,which provides the possibility for the later invocation of the interface to obtain the meteorological data of the shed,and expands the service area of the system.In this study,evapotranspiration model and information technology are effectively combined to guide agricultural irrigation.The visualization platform provides data interaction and information push for irrigation decision-making,improves water use efficiency(WUE),reduces water consumption,provides technical support for vegetable water-saving production in North China,and promotes the development of agricultural water-saving information technology.