Recovery by crop and loss of nitrogen fertilizer applied in rice season in Taihu Lake region

Field micro-plot ~(15)N labeled fertilizer experiment was conducted to investigate the fate of fertilizer N applied in rice season and the residual fertilizer N recovery in the succeeding wheat season in paddy fields in Taihu Lake region. Data showed that 29%-39% of the labeled fertilizer N was present in above-ground rice crop at harvest.Turnover rate of the residual fertilizer N by the succeeding crop was low and only 2.4 %-5.2 % of the residual soil N was present in the wheat crop.After two rice-wheat rotations,11%-13% of applied labeled N remained in 0-60 cm soil(mostly in the 0- 20 cm soil);leaching of labeled urea applied in rice season was little(only 0.6 %-1.1% of the applied N accumulated in 20-60 cm soil),and the leaching of fertilizer N occurred in wheat season and the beginning flooding period of the next rice season;47 %-54% of applied fertilizer N was lost and ammonia emission and nitrification-denitrification were the main pathways.High N and high P inputs did not lead to the increase in grain yield and plant N use efficiency.