The effect of n application rate on quality of rape and coriander was studied , the results showed that application of certain amounts of n fertilizer increased the content of protein , but high n rates reduce content of protein . the health of human body , economic benefit , environment , should be considered in order to define the reasonable applying fertilizer . the economically optimal usage of nitrogen are 101 . 02kg / hm2 for rape in protect soil 222kg / hm2 for rape in land , 171kg / hm2 for coriander and irrigation are 250mm . respectively , which can improved vegetable quality , yield and less nitrate residues in the soil profile 氮肥用量和植株体内硝酸盐含量回归分析显示出两者间存在显著相关关系,结合对土壤中硝态氮淋溶及蔬菜产量和品质的进一步研究,确立了本地区的合理灌水量和施氮量:保护地和露地油菜的合理灌水量为250mm ,施氮量分别为101 . 0kg hm ~ 2 、 222 . 5kg hm ~ 2 ,芫荽的合理灌水量为250mm ,最高施氮量为171 . 6kg hm ~ 2 。