Abstract: 【Objective】In intensive vegetable growing areas in China, the traditional high water and fertilizer inputs led to high soil nitrogen accumulation and nitrogen leaching into the deep layers of soil or groundwater, thus resulting in contamination of groundwater. Growing catch crops could control and reduce migration deep nitrate-nitrogen accumulation in soil to groundwater, therefore, this study was conducted to investigate the effects of different catch crops species on reducing nitrate accumulation in soil profile and crop growth in the next season, select the appropriate catch crop species. 【Method】The field experiment was conducted in the traditional cropping systems of greenhouse in North China Plain. In the fallow period of vegetables, deep roots-catch crops including sweet corn, amaranth, and sweet sorghum were planted in order to employ their root systems, fast growing and large amount of nitrogen uptake to promote soil nitrate nitrogen consumption, reduce nitrate accumulation in the root layer of soil profile and nitrate leaching of soil profile. Fallow field plots were also designed. Soil, plant and root samples were collected and measured, and the reduction effects of different catch crop species were analyzed.【Result】The results indicated that among the three species, sweet corn was the best in biomass production, N uptake, and root length density. From the effect of soil profile NO₃^--N reduction, sweet corn was the best among them, the reduction of NO₃^--N was 153.76, 605.70, and 56.3 kg·hm^-2 in 2008, 2009, and 2010. In the first quarter, the previous crop of cucumber was the highest in yield, N uptake and biomass production, and there was a significant difference with others in yield and N uptake. In the second and third quarters, there were no too clear difference in yield, N uptake and biomass production. Catch crops had little effect on vegetable production, but also reduced the accumulation of soil NO₃^--N. The N deficient ullage of sweet corn-cucumber was larger in 0-200 cm soil layer of the N apparent balance, which showed that sweet corn could obviously reduce the accumulation of soil NO₃^--N in the N apparent balance. Planting catch crops could obtain economic and ecological profits, and farmers obtained higher economic profits from sweet corn, amaranth and sweet sorghum, the values were 39 467, 497 and 16 522 yuan/hm², respectively.【Conclusion】Catch crops planted in greenhouse in summer could not only reduce nitrate accumulation in the root layer of soil profile, but also have little effect on cucumber production and obviously reduced the accumulation of soil NO₃^--N. In greenhouse vegetable crop rotation system, the introduction of catch crops is feasible, sweet corn is a better catch crop species.

Key words: catch crops, NO₃^--N accumulation, cucumber, yield