Effects of Nitrogen Reduction Combined with Organic Manure Application on Soil Physicochemical Properties and Crop Yield

In order to improve the recycling efficiency of livestock manure and other agricultural wastes in the process of agricultural production, improve soil fertility, and promote crop yield and income. A trial of organic manure returned to the field with reduced N fertiliser was carried out at Baoquanling Farm in the spring of 2022, with five treatments of no chemical fertiliser（CK）, local conventional fertiliser（FFP）, optimised fertiliser application（OPT）, organic manure replacing 15% N（OPT-1）, and organic manure replacing 30% N（OPT-2） at the reproductive stage, to study the effects of organic manure and reduced N fertiliser on soil physicochemical properties and maize yield. The results showed that at the nodulation stage, compared with the conventional fertiliser application（FFP）, the soil organic matter and quick-acting potassium content of the organic manure replacing 30% N treatment（OPT-2） were significantly increased by 14.28% and 6.71%, respectively, and the soil organic matter and quick-acting potassium content of the organic manure replacing 15% N treatment（OPT-1） were significantly increased by 10.20% and 11.32%, respectively. Compared with the optimised fertilisation treatment（OPT）, the soil organic matter content of the OPT-2 treatment was significantly increased by 7.63%, and the soil quick-acting potassium content of the OPT-1 treatment was significantly increased by 7.01%. At maturity, compared with the FFP treatment, the soil organic matter, alkaline dissolved nitrogen and quick-acting potassium contents of the OPT-2 treatment increased by 15.60%, 9.64% and 6.83%, respectively, and the maize yield increased significantly by 8.46%, while that of the OPT-1 treatment increased by 10.33%, 5.26% and 10.62%, respectively, and the maize yield increased significantly by 5.14%. Compared with OPT treatment, OPT-2 treatment soil organic matter and alkaline dissolved nitrogen content significantly increased by 11.09% and 8.93%, respectively, and OPT-1 treatment soil organic matter, alkaline dissolved nitrogen and quick-acting potassium content significantly increased by 6.03%, 4.57% and 5.80%, respectively. Comprehensive analysis, the application of organic manure can improve soil physicochemical properties, increase maize yield, and improve the quality of seeds, of which, 30% organic manure instead of nitrogen fertiliser（OPT-2） has the best application effect.