【Objective】Livestock manure recycling in farmland is an effective measure to dispose of livestock waste, reduce chemical fertilizer usage, and achieve green sustainable development in agriculture. Based on a two-year field experiment, this study explored the impacts of applying different types of manure under reduced chemical fertilization on crop yield, nutrient uptake, and utilization efficiency in a rice-rapeseed rotation system, which aimed to provide scientific guidance for the rational application of manure in rice-oilseed rape rotation production systems.【Method】The field trial was conducted in Dafasi Town, Wuxue City, Hubei Province, from 2022 to 2024. Under the condition of straw return to the field, the trial was set up with seven treatments: conventional fertilization (Con), 15% nitrogen fertilizer reduction on the basis of Con (85%N), pig biogas slurry fertilizer application on the basis of Con replacing 15% chemical nitrogen fertilizer (85%N+PS), Con application on the basis of chicken manure-based solid fertilizer to replace 15% chemical nitrogen fertilizer (85%N+CM), 30% nitrogen fertilizer reduction on Con basis (70%N), pig biogas slurry fertilizer to replace 30% chemical nitrogen fertilizer on Con basis (70%N+PS), and chicken manure-based solid fertilizer to replace 30% chemical nitrogen fertilizer on Con basis (70%N+CM). Based on the crop yield, yield constituting factors, and nutrient accumulation in conjunction with the nutrient harvest index, nutrient apparent balance and fertilizer contribution rate were analyzed comprehensively. 【Result】The results of the two-season experiment showed that the application of different types of manure under the condition of nitrogen fertilizer reduction could improve the crop yield and nutrient uptake of the rice-oilseed rape rotation system. There was no significant difference in yield, nitrogen and potassium accumulation and harvest index of oilseed rape and rice under 85%N+CM and 85%N+PS treatments compared with Con treatment. However, different types of manure showed significant effects on enhancing crop nutrient uptake and regulating the annual nutrient balance across the rotation cycles, and the 85%N+CM treatment significantly increased the phosphorus accumulation in oilseed rape and rice (the increases were 22.1%-24.8% and 16.6%-16.9%, respectively), but the annual phosphorus surplus and profit and loss ratio increased by 155.9% and 60.3%, respectively, due to the large amount of phosphorus input brought by chicken manure-based solid fertilizer. In contrast, the 85%N+PS treatment reduced the annual nitrogen and phosphorus surplus by 23.5% and 5.9%, respectively, and the corresponding profit and loss ratios decreased by 17.9% and 6.7%, respectively, while maintaining crop nutrient uptake. Compared with 85%N+CM treatment, the FCR of 85%N+PS treatment in oilseed rape and rice increased by 17.4%-27.0% and 24.1%-35.5%, respectively, this not only achieved an efficient substitution of chemical N fertilizer but also substantially alleviated the pressure of soil nutrient surplus : the surplus of nitrogen, phosphorus and potassium was reduced by 28.6%, 63.2% and 35.5%, respectively, and the profit and loss ratio was reduced by 19.3%, 41.8% and 20.5%, respectively. When the nitrogen reduction ratio reached 30% (70%N+CM/PS), compared with the 85%N+CM/PS treatment, the yield of oilseed rape and rice decreased by 7.2%-18.5% and 6.9%-15.7%, respectively, and the accumulation of nitrogen, phosphorus and potassium in the shoots decreased significantly, the annual nutrient surplus and profit and loss ratio increased. 【Conclusion】In conclusion, compared with conventional fertilization, the application of different types of manure under the condition of a 15% reduction in nitrogen could not only ensure the crop yield of the rice-oilseed rape rotation system, but also effectively promote the absorption of nutrients by crops, among them, combined with pig biogas liquid fertilizer (85%N+PS) treatment to further improve nutrient uptake and FCR while maintaining yield, and reduce the annual nutrient surplus of rotation, and achieve the level of conventional fertilization. Therefore, it was recommended as the best manure return model for the rice-oilseed rape rotation system.
