Effects Of Combined Application Of Nitrogen And Phosphorus On Material Accumulation And Absorption And Utilization Of Nitrogen And Phosphorus In Intercropping Soybean

The reasonable fertilization method in corn-soybean intercropping can not only reduce the planting cost,but also increase the yield of soybean corn and bring the land equivalent ratio advantage of intercropping into full play.Study on four nitrogen levels（N1:0 kg/hm²（N）;N2:15 kg/hm²（N）;N3:45 kg/hm²（N）;N4:75 kg/hm²（N））and four phosphorus levels（P1:0 kg/hm²（P₂O₅）;P2:45 kg/hm²（P₂O₅）;P3:90 kg/hm²（P₂O₅）;P4:135 kg/hm²（P₂O₅））by split Zone experiment.Effects of interactive application on soybean material accumulation,yield formation,nitrogen and phosphorus absorption and utilization efficiency under corn-soybean intercropping system.The results are as follows:（1）yield and yield compositionWith the increase of nitrogen application rate,the yield of soybean increased at first and then decreased,and the appropriate amount of phosphorus application at the same nitrogen application level was helpful to the increase of soybean yield.The yield of soybean reached the peak value in N2P4 treatment,which was 1641.6 kg/hm².Efficient utilization of nitrogen and phosphorus.Although the application of nitrogen and phosphorus in yield components decreased the number of pods of soybean,it increased the number of seeds per pod more significantly,thus promoting the increase of the number of grains per plant of soybean.The number of grains per plant reached the peak value of 102.59 in N2P4 treatment.The 100-grain weight was not significantly affected by nitrogen and phosphorus.（2）accumulation and distribution of substancesThe proper application of nitrogen fertilizer and phosphorus fertilizer is beneficial to the material accumulation of soybean.The amount of phosphorus needed to reach the peak value of material accumulation was different at different levels of nitrogen application.The peak value of material accumulation was 57.02 g of treated N3P4,and the maximum growth rate of material accumulation appeared late after 77.46 d sowing.There was no significant difference between the dry matter accumulation of 56.78 g of N2P4 and that of N3P4,and the maximum growth rate of dry matter accumulation was2.64 d earlier than that of N3P4,which provided a sufficient amount of dry matter accumulation for the drum grain of soybean.The combined application of nitrogen and phosphorus was also beneficial to the dry matter accumulation of soybean leaves and photosynthesis of soybean.In the middle of N2P2 treatment,the proportion of dry matter was the largest,with a value of 60.45%.（3）Accumulation and distribution of nitrogen and phosphorus nutrientsThe combined application of nitrogen and phosphorus fertilizer was beneficial to increase the accumulation of nitrogen and phosphorus in pre-anthesis leaves and post-anthesis grains of soybean.At R2 stage,the accumulation of leaf nitrogen increased at first and then decreased with the increase of phosphorus application,but the effect of nitrogen was not significant.The interaction of nitrogen and phosphorus significantly increased the nitrogen accumulation of leaves,and reached the peak 36.49kg/hm² in N3P2 treatment.The grain nitrogen accumulation in R8 stage was affected by nitrogen and phosphorus,which increased at first and then decreased with the increase of fertilizer application.The interaction of nitrogen and phosphorus reached the peak 110.43 kg/hm² of nitrogen accumulation during N2P4 treatment.At the same time,nitrogen harvest index,absorption efficiency and production efficiency reached the maximum values of 70.24%,11.31kg/kg and 10.41 kg/kg in the treatment of N1P2,N2P3 and N1P2,respectively.Phosphorus was mainly accumulated in the stem of R2soybean.The application of nitrogen fertilizer was beneficial to the accumulation of phosphorus in the stem,but phosphorus had no significant effect on it,and reached the peak 4.6 kg/hm² in the treatment of N4P2.Nitrogen and phosphorus in R8 stage could significantly improve the phosphorus content,phosphorus harvest index and absorption efficiency of soybean seeds,and their peak values reached 17.03 kg/hm²,74.38%and0.5 kg/kg at N2P4,N3P3 and N3P2,respectively,but the phosphorus production efficiency was not significantly improved.（4）number and weight of soybean nodulesThe combined application of nitrogen and phosphorus had a significant effect on soybean nodulation.Nitrogen application could promote soybean nodulation,but excessive nitrogen application could inhibit nodulation.At low nitrogen level,the application of phosphorus fertilizer could promote the formation of soybean nodules and increase the number and weight of nodules.In R1 stage,the application of excessive nitrogen fertilizer（N4）would inhibit the nodulation of soybean,while the application of additional phosphorus would promote the nodulation of soybean,and the combined application of nitrogen and phosphorus was more beneficial to increase the nodulation number of soybean in R1 stage.In R3 stage,due to the serious shading of corn row,the root nodules were not significantly affected by nitrogen and phosphorus.In R5 stage,the number of soybean nodules increased at first and then decreased with the increase of phosphorus content,and reached the peak at P3.Nitrogen application decreased the nodulation number of soybean.The interaction of nitrogen and phosphorus will reduce the inhibitory effect of nitrogen fertilizer on nodulation.The largest number of nodules in R5 stage is N2P4,and its value is 109.75.At R1 and R3stage,the fresh weight of soybean root nodules increased at first and then decreased with the increase of nitrogen application.Nitrogen application at R5 stage could only reduce the fresh weight of root nodules.The combined application of nitrogen and phosphorus will significantly increase the fresh weight of root nodules in each stage.（5）Utilization efficiency of nitrogen and phosphorus fertilizerThe maximum nitrogen partial productivity and agronomical utilization efficiency of N2P4 were 109.44 kg/kg and 33.70 kg/kg,respectively,which were 417.20%and1418%higher than that of N4P1,respectively.The partial productivity and agronomical utilization efficiency of phosphate fertilizer decreased with the increase of fertilizer application,and the peak value appeared in N1P2.The partial productivity and agronomical utilization efficiency of N2P4 decreased compared with N1P2.