Abstract: 【Objective】The effects of nitrogen (N) fertilization management on crop yield, total N accumulation and partial factor productivity were studied under the condition of returning residues in different paddy-upland rotations. 【Method】Field experiments were conducted in 14 counties (e.g., Xiaonan, Songzi, Yingcheng) of Hubei Province under rice-oilseed rape and rice-wheat rotation systems in the period of 2013-2014. Five treatments were followed as: 1) Conventional N fertilization in 3  times, 2) conventional N fertilization in 3 times with residues incorporation, 3) high N fertilization rate in 3 times with residues incorporation, 4) N fertilization in 2 times, and 5) N fertilization in 2 times with residues incorporation. Crop yields (rice, rapeseed and wheat), total N accumulation and partial factor productivity were analyzed among the treatments.【Result】 Crop yield, aboveground biomass and total N accumulation were not affected by high N application rate under residue incorporation in the rice-oilseed rape rotation but were significantly increased in the rice-wheat rotation. Compared with conventional N fertilization in 3 times for the rice-wheat cropping rotation, high N fertilization rate in 3 times with residues incorporation rice and wheat yield increments were 0.632 and 0.564 t·hm^-2 on average, with the increasing rates of 6.85% and 10.67%, respectively. Aboveground biomass increments were 1.50 and 1.07 t·hm^-2 on average, with increasing rates of 8.11% and 9.06%, respectively. Total N accumulation increments were 11.54 and 23.57 kg·hm^-2 on average, with increasing rates of 7.88% and 21.28%, respectively. Total N accumulation of rice and wheat increment was 35.11 kg·hm^-2, with increasing rate of 13.65%. N application at 2 times with residues incorporation would satisfy crop yield and total N accumulation compared with conventional N fertilization at 3 times. Specifically for the rice-wheat rotations, rice and wheat yield increments were 0.439 and 0.385 t·hm^-2 on average, with increasing rates of 5.12% and 7.63%, respectively. Total N accumulation increments were 11.09 and 21.06 kg·hm^-2 on average, with increasing rates of 8.26% and 20.82%, respectively. Total N accumulation increment was 32.14 kg·hm^-2 for the rice-wheat cropping rotation, with increasing rate of 13.66%. For N efficiency, regular application rate of N obtained high partial factor productivity of applied N (PFP_N, averaged values of PFP_N were 52.03 to 59.29 kg·kg^-1 for rice, 10.62 to 11.12 kg·kg^-1 for oilseed rape, and 33.63 to 36.20 kg·kg^-1 for wheat), partial factor productivity of applied N (PFP_N) with residues incorporation was better than that without residues incorporation for equal nitrogen rates, especially when we moved N fertilizer forward with residues returning. For rice-oilseed rape rotation system, Compared with conventional N fertilization at 3 times and N fertilization in 2 times, conventional N fertilization in 3 times with residues incorporation and N fertilization in 2 times with residues incorporation the PFP_N of rice increments were 2.45 and 4.07 kg·kg^-1 on average, with increasing rates of 4.36% and 7.37%, respectively. Oilseed rape increments were 0.36 and 0.49 kg·kg^-1 on average, with increasing rates of 3.38% and 4.62%, respectively. For rice-wheat rotation system, rice increments were 3.88 and 1.64 kg·kg^-1 on average, with increasing rates of 7.46% and 3.10%, respectively. Wheat increments were 1.60 and 1.93 kg·kg^-1 on average, with increasing rates of 4.75% and 5.65%, respectively. Compared with conventional N fertilization at 3 times, the PFP_N values of rice and oilseed rape would increase 5.68% and 4.00% under N Fertilization at 2 times with residues incorporation, respectively. For the rice-wheat rotation system, N application at 2 times with residues incorporation would increase the PFP_N values by 5.12% and 7.63% for rice and wheat, respectively.【Conclusion】With residues returning, moving fertilizer-nitrogen forward would achieve high and stable crop yield and enhance N efficiency under different paddy-upland rotations.

Key words: residues returning, nitrogen managements, crop yield, rice-oilseed rape rotation, rice-wheat rotation, nitrogen use efficiency