Soil nitrate accumulation and leaching in conventional, optimized and organic cropping systems

Excessive nitrogen (N) and water input, which are threatening the sustainability of conventional agriculture in the North China Plain (NCP), can lead to serious leaching of nitrate-N (NO3--N). This study evaluates grain yield, N and water consumption, NO3--N accumulation and leaching in conventional and two optimized winter wheat-summer maize double-cropping systems and an organic alfalfa-winter wheat cropping system. The results showed that compared to the conventional cropping system, the optimized systems could reduce N, water consumption and NO3--N leaching by 33, 35 and 67-74%, respectively, while producing nearly identical grain yields. In optimized systems, soil NO3--N accumulation within the root zone was about 80 kg Nha most of the time. In the organic system, N input, water consumption and NO3--N leaching was reduced even more (by 71, 43 and 92%, respectively, compared to the conventional system). However, grain yield also declined by 46%. In the organic system, NO3--N accumulation within the root zone was generally less than 30 kg Nha. The optimized systems showed a considerable potential to reduce N and water consumption and NO3--N leaching while maintaining high grain yields, and thus should be considered for sustainable agricultural development in the NCP.