| In order to reduce the chemical fertilizer application and increase the nitrogen use efficiency of spring wheat in Northeast China and ensure the ecological environment safety and sustainable development of farmland,the effects of partial substitution of chemical nitrogen fertilizer with organic fertilizer and stage fertilization on soil fate of nitrogen and spring wheat nitrogen use efficiency were investigated.Through field experiments,five treatments were set up,which were no nitrogen treatment（CK）,conventional nitrogen treatment（CF）,organic fertilizer instead of25%chemical fertilizer nitrogen（N1）,organic fertilizer instead of 25%chemical fertilizer nitrogen and applied in two stages（N2）and three stages（N3）.The effects of chemical fertilizer application by stages on soil nitrogen nutrient,soil organic matter,NH4+and NO3-transformation,soil enzyme activity,NH3 volatilization and N2O emission,nitrogen accumulation and nitrogen efficiency of spring wheat were studied and analyzed in this paper.The results show that:（1）N1 and N2 treatments could significantly increase the contents of total nitrogen,available nitrogen and soil enzyme activities at seeding,jointing and booting stages of spring wheat.The activities of soil urease and nitrate reductase were increased most significantly and there was no significant effect on soil organic matter;（2）Organic fertilizer replacing 25%of chemical fertilizer nitrogen could significantly increase the contents of NH4+and NO3-in the surface soil,but NH4+and NO3-had no obvious downward migration.From 25%chemical nitrogen fertilizer replaced by organic fertilizer and chemical nitrogen fertilizer applied in stages on this basis,the contents of NH4+and NO3-in the0～10 cm soil layer was N1>N2>N3;（3）Organic fertilizer instead of 25%chemical fertilizer with a one-time into the chemical fertilizer can significantly reduce NH3 volatilization and N2O emission rate,reduce nitrogen loss;（4）The effect of increasing spring wheat yield was N1>N2>CF>N3,respectively.Compared with CF,N1 and N2 significantly increased yield by 21.33%and 16.64%,while N3 yield decreased by 7.09%.From the agronomic efficiency of nitrogen fertilizer,N1>N2>CF>N3,compared with CF,N1 and N2 significantly increased by 66.00%and 51.45%,N1 treatment had the best effect on spring wheat yield and N use efficiency improvement;（5）Correlation analysis showed that there were significant positive correlations between wheat yield and the contents of nitrogen in the soil at joining and booting stages,soil urease activity and NH3 volatilization and N2O emission rate,and wheat yield and grain nitrogen accumulation and agronomic efficiency of nitrogen fertilizer.According to the heat map analysis of related factors under different treatments,organic fertilizers to replace 25%of one-time nitrogen fertilizer under the foundation before planting and before sowing and jointing stage nitrogen were more beneficial to increase soil nutrient content and soil enzyme activity,reduce nitrogen loss,increase grain nitrogen accumulation and wheat nitrogen efficiency.Combining with the characteristics of spring wheat growth and the north comprehensive analysis on characteristic of soil and climate conditions,compared with the conventional chemical fertilizers,organic fertilizers to replace 25%of one-time nitrogen fertilizer under the foundation before planting and before sowing and jointing stage nitrogen can effectively improve the soil nutrient content,spring wheat yield and nitrogen use efficiency,reduce the NH3 volatilization and N2O emissions significantly,reduced nitrogen loss.In order to reduce the stage fertilization increased manpower and machinery costs,comprehensive analysis suggested that on the basis of organic fertilizer instead of 25%nitrogen fertilizer,fertilizer in one-time plowing the soil before sowing would be more advantageous to increase spring wheat yield and economic benefits. |
