Study On Nitrogen Reducing And Increasing Effect Of Combined Application Of Chemical Fertilizer And Amino Acid Fertilizer In Winter Wheat-Summer Maize Rotation System

The main planting method in the North China Plain is a winter wheat-summer maize rotation system.In this rotation system,there is a very common phenomenon of excessive fertilization.If the input nitrogen fertilizer exceeds the nitrogen requirement for the highest yield of the crop,it will not only reduce crop yield,but also significantly increase the loss of nitrogen fertilizer,resulting in reduced fertilizer utilization.A large amount of nitrogen fertilizer applied to farmland is not used by crops,part of which will cause nitrogen fertilizer loss through leaching and surface runoff,and part of the nitrogen fertilizer that was not absorbed by previous crops can be fully absorbed in subsequent crops.The stable isotope ¹⁵N tracer technology to study nitrogen in crops and soil is a mature detection method,which can not only distinguish the source of nitrogen in the process of crop growth and development,but also track the absorption and utilization of nitrogen in the crop.Because amino acids have small molecules and are easily absorbed by plants,they can be used as fertilizers to provide organic nitrogen sources for plants.To a certain extent,the reasonable combination of chemical fertilizers and amino acid fertilizers can increase crop yields,effectively improve crop quality,improve soil physical and chemical properties,and improve soil fertility.The study aimed at the problems of high nitrogen fertilizer application and reduced fertilizer utilization in the winter wheat-summer maize rotation in the North China Plain.¹⁵N tracer technology and pot experiment were used to build a crop rotation system.By reducing the amount of fertilizer nitrogen applied and applying amino acids in a reduced proportion to increase crop yield and nitrogen utilization efficiency without reducing yield compared with conventional fertilization.Then,determine the maximum nitrogen reduction of conventional fertilizers and the maximum substitution of amino acid fertilizers in the winter wheat-summer maize rotation system.Finally,the optimal ratio of amino acid fertilizer and chemical fertilizer was selected through multiple linear regression analysis（MLRA）.This experiment set up 7 treatments,namely:（I）no fertilizer treatment（CK）;（II）only phosphate fertilizer and potassium fertilizer（PK）;（III）urea(N₁₀₀PK+AA₀);（IV）urea reduction 10%+5%amino acid fertilizer(N₉₀PK+AA₅);（V）urea reduction20%+10%amino acid fertilizer(N₈₀PK+AA₁₀);（VI）urea reduction 30%+15% amino acid fertilizer(N₇₀PK+AA₁₅);（VII）Urea reduction 40%+20%amino acid fertilizer(N₆₀PK+AA₂₀).The results showed:Studies have shown that in the corn season,the yield of the treatment with 10% nitrogen reduction and 5% amino acid application was the highest,which was 14412 kg/hm².Compared with the conventional fertilization treatment,the yield,the amino acid nitrogen utilization rate,nitrogen accumulation,nitrogen fertilizer agronomic efficiency,nitrogen partial productivity,urea nitrogen utilization rate,total nitrogen utilization rate and ¹⁵N fertilizer utilization rate were increased by13.76%,10.67%,7.16%,27.19%,19.15%,3.36%,9.66%,and 3.36%,respectively.The content of crude protein and crude starch were also increased.Comparing the optimized path coefficients,the most positive impact of the corn season on yield was the alkali hydrolyzed nitrogen content（P<0.01）,and the most negative impact was the available potassium content（P<0.01）.Under the premise of ensuring that the yield of maize was not reduced by normal fertilization treatment,the 12.6% reduction of nitrogen and the 6.3% of amino acid fertilizer were the maximum potential upper limit for amino acid fertilizer to replace chemical fertilizer to reduce nitrogen and increase efficiency.Under the premise that the partial productivity of nitrogen fertilizer did not decrease under the normal fertilization treatment of maize,in the maize season,the fertilization condition of 20.78% reduction of nitrogen and 10.39% of amino acid fertilizer was the maximum potential upper limit for replacing chemical fertilizers to reduce nitrogen and increase efficiency.In the wheat season,the treatment with 10% nitrogen reduction and 5% amino acid application had the highest yield of 4082 kg/hm².Compared with conventional fertilization treatment,the yield,amino acid nitrogen utilization rate,the content of nitrogen accumulation,the agronomic efficiency of nitrogen fertilizer,the partial productivity of nitrogen fertilizer,the utilization rate of urea nitrogen fertilizer,total nitrogen fertilizer increased,and the utilization rate of ¹⁵N fertilizer increased by3.42%,29.03%,1.03%,14.92%,7.01%,3.29%,8.53%,and 31.03%,respectively.The content of crude protein,crude fat and crude starch all also increased.By comparing the optimized path coefficients,the most positive influence of wheat season on yield was the content of alkaline hydrolyzed nitrogen（P<0.05）,and the most negative influence was the content of available potassium（P<0.05）.On the premise of ensuring that the normal fertilization of wheat does not decrease,the nitrogen reduction of 21.6% and the application of amino acid fertilizers 10.8% are the maximum potential upper limit for amino acid fertilizers to replace chemical fertilizers to reduce nitrogen and increase efficiency;under the premise of ensuring that the normal fertilization of nitrogen fertilizers does not decrease the partial productivity of wheat,the nitrogen reduction is 50.18% and amino acid fertilizer is 25.09%,which is the maximum potential upper limit for partial productivity of nitrogen fertilizer.