Using EU-Rotate_N Simulated High Underground Water And Nitrogen Dynamics Of Several Important Protected Vegetables Under Water Level

To pursuit high yield,the excessive application of water and fertilizer are popular in Chinese greenhouse vegetable production,which led to high residual nitrate levels in soil excessive nitrate leaching and nitrate contamination of groundwater.The soil pollution is becoming one of the limiting factor of sustainable development of greenhouse vegetable production.Fertigation is one of the ways to solve this problem.However,current fertigation technology mainly depends on the farmers’ experience,rather than the the water and nutrient requirement.Thus,building water and nitrogen model is critical to achieve accurate irrigation and fertilization fro greenhouse vegetable production.The EU-Rotate_N model is a model used in the study of crop water and nitrogen dynamics in European.In China,some scholars in northern China have used this model to simulate the water and nitrogen requirement of wheat,cucumber,and tomato.Unlike the regions mentioned above,some area of Jiangsu province is rich in precipitation and high in groundwater table.Thus,the model can not be directly applied in in region due to the differences of vegetable species,cultivars,and type of greenhouse,climatic and soil conditions.In this study,different nitrogen treatments were applied for three important greenhouse vegetables,pakchoi(Brassica campestris L.ssp.),cucumber(Cucumis sativus L.)and tomato(Lycopersicon esculentum Mill.),and the soil water content,nitrate nitrogen content,dry matter and yield of different soil layers were measured.Some parameters of EU-Rotate_N were calibrated and the indexes mentioned above were simulated in a region in Jiangsu province with shallow water talbe.The results are as follows:During the growth of greenhouse vegetables,the simulated values of soil moisture and nitrate nitrogen at different soil depths are in good agreement with the measured values.The soil water content Nash-Sutcliffe model efficiency coefficient(NSE)and model consistency(d)of the pakchoi test were 0.376-0.785,0.895-0.964,respectively;the statistical index range of soil nitrate nitrogen content was 0.365-0.715,0.803-0.940,respectively The range of the statistical index of soil water content in the greenhouse cucumber test was 0.360-0.913,0.851-0.980,and the range of the statistical index of soil nitrate nitrogen content was 0.412-0.698,0.886-0.938,respectively.The range of the statistical index of soil water content in the facility tomato experiment was 0.367-0.749,0.856-0.947,and the range of the statistical index of soil nitrate nitrogen content was 0.365-0.698,0.869-0.932,respectively.Moreover,the dry weight and yield simulation effects of the three kinds of facility vegetables are all good.The results show that the EU-Rotate N model is effective in simulating soil water content,nitrate nitrogen content,dry matter quality and yield.This indicates that the improvement of the EU-Rotate N model is successful.The improved model can be used in Jiangsu Province and other high groundwater regions and provide a useful tool for the water and nitrogen management of greenhouse pakchoi,cucumber,and tomato production.Based on the simulation results with or without a groundwater table algorithm and measured values,no difference of soil surface moisture(0-10 cm)were found between soil with high and normal groundwater tables.However,a higher groundwater table tends to increases the moisture in 10-30 cm soil and mineralization,reduces the ammonia volatilization and nitrogen leaching,and finally increases the nitrogen accumulation in the 0-30 cm soil.