Influence of Different Nitrogen Fertilizer Rate on the Yield of Greenhouse Eggplants and Nitrate Content

The influence of different nitrogen fertilizer rate on the eggplant yield and the nitrate content were explored through field tests.Results show that based on the application of 1 500 kg duck feces,7.5 kg P2O5 and 24 kg K2O every 667 m2,the nitrogen rate has a remarkable correlation with the yield.The yield increases in certain scope with the addition of fertilizer amount,but it decreases with the addition of fertilizer amount when the fertilizer surpasses some critical value.A mathematical model for the relationship between nitrogen fertilizer rate and the yield is Y=1 698.770 2+43.247 1X-0.870 807X2.In the period of initial fruiting,full bearing and end fruiting,the nitrate contents(Y) of eggplant fruits under different nitrogen levels(X) were measured.The fitting mathematical models are Y=124.708 0+2.280 9X,Y=98.160 0+2.088 0X,and Y=163.09+1.438 4X respectively.The nitrate content of eggplant fruits increases with nitrogen fertilizer rate,showing a significant correlation.