蔬菜间作对土壤和蔬菜硝酸盐累积的影响

大量氮肥施用，易造成菜地土壤硝酸盐累积并引起地下水硝酸盐污染和蔬菜硝酸盐含量超标。为降低菜田氮素累积及环境污染风险，采用根深差异蔬菜间作的方法，研究其对土壤硝态氮时空变异规律和蔬菜硝酸盐含量的影响，选择根系较深的萝卜和根系较浅的芹菜进行间作种植大田试验。结果表明，无论在作物的生长前期还是收获期，此种间作增加了0～20cm土层NO3^- -N含量，同时降低了20cm以下土层NO3^- -N含量，能够减少土壤中NO3^- -N的向下移动。从土壤NO3^- -N累积剖面分布规律看，间作区0～40cm土层NO3^-—N累积量高于单作区，而40～100cm土层NO3^- -N累积量低于单作区，间作区土壤0—100cm土层NO3^- -N总累积量减少，收获期分别比萝卜和芹菜单作区降低1．4％、9．0％。间作有降低萝卜和芹菜硝酸盐的趋势，而间作区萝卜全氮含量显著高于单作区，同时间作显著提高了萝卜产量，此种间作还能够减少氮素的表观损失。总之，合理搭配的蔬菜间作既能够增强土壤对氮素的保蓄能力，减少土壤NO3^- -N淋移，对蔬菜产量和品质也有一定正效应。

Effect of Vegetable Intercropping on the Nitrate Accumulation in Soil Profiles and Vegetables

Soil nitrate accumulation was often occurred because of excessive nitrogen fertilization application which easily led to nitrate pollution of groundwater and vegetable. The aim of this study was to determine the variation of nitrate in soil and crops under the intercropped system between different rooting depth vegetables, to study the temporal and spatial variation of soil nitrate, in addition, to reveal the difference of vegetables nitrate content. We selected the radish （deeper root） and celery （shallow root）, then intercropped them together. The results showed that whether in preceding growth time or the harvest, NO3-N content of 0-20 cm soil layer increased by this intercropping while, concentrations of lower layers decreased, which indicated that this intercropping could reduce nitrate leaching. Furthermore, 0-40 cm NO3^- -N accumulation of intercropping was more than that of sole crop, on the countrary, 40-100 cm NO3^- -N stored less than that of sole crop system. In the whole profile of 0-100 cm soil, NO3^- -N accumulation of the intercropping was less than that of sole radish and celery for 1.4% and 9.0%, respectively. This intercropping system has the trendency to reduce vegetable nitrate. It indicated that this intercropping has the yield advantage to some extent because that total nitrogen concentration and yield of intercropped radish evidently were higher than those of sole radish.Also, this intereropping can reduce the apparent N losses. Reasonable vegetable intercropping can increase nitrate holding ability and reduce nitrate leaching. Therefore, it has the positive effect on vegetable yield and quality.