Abstract:Soil fertility and nutrient use efficiency are the basis for sustainable food production. A field experiment was conducted to investigate the effects of different fertilization modes on nitrogen use efficiency of crops and available nutrient balance in soil with a rice-wheat rotation. The results showed that the rice shoot biomass of RF-OM and RF-S treatments with the reduced total nutrient inputs were significantly higher than that of LRF treatment (P < 0.05), similar to that of FP treatment. The differences of wheat straw biomass among the four fertilization treatments were not significant, the wheat grain biomass and shoot biomass of RF-OM and RF-S treatments were similar to that of LRF treatment. At rice harvesting stage, the nitrogen contents in the main shoot organs of RF-OM treatment was similar to those of LRF treatment, but the total nitrogen amount accumulated in shoots was significantly higher than that of LRF (P < 0.05). For wheat plants, the nitrogen contents and accumulation amounts in straws or grains of RF-OM and RF-S treatments were not significantly different from LRF treatment. At rice or wheat harvesting stage, the phosphorus contents and accumulation amounts in brown rice, rice husks, wheat straws and grains of RF-OM and RF-S treatments were not significantly different from FP and LRF treatments. As a result of increasing potassium doses, potassium contents and accumulation amounts in rice straws, rice husks and wheat straws were significantly higher than those of FP or LRF treatments (P < 0.05). Nitrogen agronomic efficiency, nitrogen apparent recovery and nitrogen partial factor productivity of RF-OM and RF-S treatments for rice or wheat were significantly higher than those of FP or LRF treatment (P < 0.05), the nitrogen grain production efficiency was also higher than that of FP or LRF treatment, even significantly (P < 0.05). At rice or wheat harvesting stage, soil exchangeable and slow-release potassium concentrations of RF-OM and RF-S treatments with raising potassium dosages were significantly higher than those of FP and LRF treatments. Soil alkali-hydrolyzed nitrogen concentrations at rice harvesting stage and soil available phosphorus concentrations at wheat harvesting stage of RF-OM and RF-S treatments were not significantly different from LRF treatment. After a whole rice-wheat rotation, concentrations of soil available nutrients (alkali-hydrolyzed nitrogen, available phosphorus, exchangeable potassium, slow-release potassium) of the four fertilization treatments were all higher than those of the initial soil. Organic manure used as an alternative for chemical fertilizers is able to significantly increasing crop nitrogen use efficiency, being conducive to the balance of soil available nutrients and significant increases in the concentrations of soil exchangeable potassium and slow-release potassium, which can be regarded as a suitable technique for reducing application of chemical fertilizers, stabling grain yields and increasing fertilization efficiency in rice and wheat cropping.