Effects Of Water And Nitrogen Supply On Nitrate Accumulation In Vegetable-soil Production System

It is a serious issue that water and nitrogen input rates are unreasonable high in vegetable production in china, which may increase nitrate accumulation in vegetable and ground water contamination. In result, these will be harmful to people's health. The objectives of this paper which based on column % pot and micro-plot experiments were to compare the effects of different water and nitrogen supply strategies on nitrogen leaching in the soil profile and nitrate accumulation in vegetable as a base for the N and water recommendations in vegetable production. The results are as follows:The nitrate contention of rape and coriander at full growth varied from seedling stage to maturing stage which is vigorous growth stage >maturing stage >seedling stage. We should choose the optimum stage: rate and coriander are 40d and 45d after coming out respectively. Vegetable nitrogen contention and nitrogen leaching in soil were strongly affected by water and nitrogen supply in the experiments. Nitrate content of rape and coriander increased with higher nitrogenous fertilizer application and lower water supply. Nitrogen leaching in the soil increased with higher nitrogenous fertilizer application and water supply in column and micro-plot experiments, especially on higher irrigation and higher nitrogenous fertilizer. There was little nitrogen leaching when N application was below 135 kg/hm2, but N use at a rate of 270 kg/hm2 increased nitrogen leaching in the soil.Water and nitrogen are two important factors which strongly affect vegetable growth. There were no significant differences in marketable yield between irrigation at rate of 250mm and 350mm and among N use more than 135kg/hm2, which means that much water and nitrogen fertilizer could be saved using irrigation treat 250mm and nitrogenous fertilizer with 135kg/hm2to obtain higher yield.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.