[Effects of nitrogen application on yield and nitrogen use efficiency of rapeseed (Brassica napus)]

A greenhouse pot experiment was conducted to study the effects of nitrogen application on the yield and nitrogen use efficiency of rapeseed under post anthesis waterlogging condition. Two high nitrogen use efficiency rapeseed genotypes 'Monty' and 'Xiangyou 15' and two low nitrogen use efficiency rapeseed genotypes 'R210' and 'Bin270' were treated with 3 nitrogen levels (0.05, 0.2, 0.3 g N·kg^-1soil) under waterlogging or normal water condition. The results showed that compared with the normal water condition, rapeseed pods per plant, 1000-seed mass, seed number per pod and seed yield decreased significantly under post anthesis waterlogging condition. Under the normal water condition, yield increased significantly along with the increment of nitrogen fertilizer, while under waterlogging condition the contribution of increment of nitrogen fertilizer was not significant. Compared with the low nitrogen use efficiency rapeseed genotypes, the high nitrogen use efficiency rapeseed genotypes stimulated seed filling under post anthesis waterlogging condition. Under the same water treatment, nitrogen use efficiency, nitrogen partial factor productivity, agronomic nitrogen use efficiency, nitrogen uptake efficiency and N harvest index of nitrogen fertilizer decreased significantly as the results of post anthesis waterlogging, nitrogen uptake and utilization capability of different rapeseed genotypes were affected significantly by waterlogging. Compared with the low nitrogen use efficiency rapeseed genotypes, the high nitrogen use efficiency rapeseed genotypes were more conducive to nitrogen translocation and redistribution of nitrogen to the pods under waterlogging condition, thus improving the seed production efficiency. Significant water and nitrogen interaction effects existed in rapeseed yield performance parameters, and the effects of water, nitrogen fertilizer and their interaction on rapeseed yield and yield performance parameters varied among diffe-rent genotypes.