There was positive correlation between nitrate content and nitrogen fertilization application level, in the field culture relative coefficients are follows: Chinese cabbage r=0.9629**, spinach r=0.9538*,lettuce r=0.9551*;

• 硝酸盐含量与施氮水平之间正相关；相关系数分别为:(1)田间栽培小白菜r=0.；9629(统计分析相关程度达极显著水平)；菠菜r=0