Effects Of Optimizing Nitrogen Fertilizer Management On Crop Yield And Quality In The Wheat Bean Multiple Crop System In Guanzhong Irrigation Area

The Guanzhong irrigation area is one of the main grain-producing areas in China,and realizing sustainable agriculture in this area is of great significance to ensuring China’s grain production.Nitrogen is one of the important driving factors of crop production,but the application of nitrogen fertilizer in Guanzhong irrigation area has problems such as excessive application level and low nitrogen use efficiency.Optimizing the application and management of nitrogen fertilizer is of great significance to the sustainable production of agriculture in Guanzhong irrigation area.Therefore,this study took the wheat-bean multiple cropping system as the research object,and set three nitrogen fertilizer levels:high nitrogen application level(HN:225 kg N hm^-2),medium nitrogen application level(MN:180 kg N hm^-2),low nitrogen application level(LN:135 kg N hm^-2);two types of nitrogen fertilizer:common urea（CU）,blended controlled release urea and common urea with 1:1（BU）.The effects of nitrogen application level and nitrogen fertilizer type on soil chemical properties,crop growth,yield and quality of wheat-black soybean multiple cropping system were studied to provide a theoretical basis for nitrogen fertilizer management of wheat-bean multiple cropping system in Guanzhong irrigation area.The main results are mainly as follows:（1）In the two growing seasons of winter wheat,the soil available phosphorus,nitrate nitrogen and total nitrogen content in the mature stage of winter wheat increased with the increase of nitrogen application level;compared with CU,the available phosphorus and total nitrogen under BU treatment increased by 3.53%-18.76%and 1.03%-11.76%,nitrate nitrogen decreased by 14.35%-27.53%.In the two growing seasons of black soybean,the soil p H at the maturity stage decreased with the increase of nitrogen application level,while the nitrate nitrogen and total nitrogen content increased with the increase of nitrogen application level;compared with CU,the p H and total nitrogen under BU treatment Respectively increased by 0.90%-3.85%and 2.50%-5.66%,nitrate nitrogen decreased by3.16%-19.05%.（2）In the two growing seasons of winter wheat,the tiller number,plant height,dry matter accumulation,leaf area index,SPAD value and photosynthetic characteristics of winter wheat all increased with the increase of nitrogen application level,but the overall no significant difference.Compared with CU,the dry matter accumulation in mature stage increased by 1.28%-4.85%under BU treatment.In the two growing seasons of black soybean,the plant height,dry matter accumulation,SPAD value and photosynthetic characteristics of black soybean all showed MN>LN>HN.Compared with CU,the plant height,dry matter accumulation and net photosynthetic rate under BU treatment increased by0.17%-3.05%,1.35%-6.00%and 4.83%-11.16%,respectively.（3）In the two growing seasons of winter wheat,the yield of winter wheat increased with the increase of nitrogen application level,but there was no significant difference between the levels of MN and HN;compared with CU,the yield of winter wheat and the number of spikes per unit area under the BU treatment increased by 1.45%-5.93%and1.49%-6.69%.In addition,compared with CU,the crude protein content of winter wheat under BU treatment increased by 2.28%-4.97%.In the two growing seasons of black soybean,the yield of black soybean increased first and then decreased with the increase of nitrogen application rate,and the yield of black soybean under the MN level was the highest,which was significantly increased by 11.96%-12.59%and 5.56%-9.44%compared with LN and HN;At the MN level,compared with CU,the number of pods per plant and the yield of BU treatment were significantly increased by 17.20%-18.10%and 8.51%-14.86%,respectively.The type of nitrogen fertilizer also significantly affected the crude protein content of black soybean.Compared with CU,the crude protein under BU treatment increased by 0.35%-1.35%.（4）During the two growing seasons of winter wheat,the nitrogen accumulation of winter wheat increased with the increase of nitrogen application level.Compared with CU,BU treatment significantly increased the nitrogen accumulation and the transfer and contribution rate of vegetative organs to the grain of winter wheat.In addition,compared with CU,the NPE（Nitrogen Fertilizer Physiological Use Efficiency）,NAE（Nitrogen Fertilizer Agronomic Use Efficiency）and PFP（Nitrogen Fertilizer Partial Productivity）of winter wheat under BU treatment increased by 2.82%-18.11%,7.09%-29.71%and1.46%-5.93%,respectively.In the two growing seasons of black soybean,the amount of nitrogen application and the type of nitrogen fertilizer significantly affected the nitrogen accumulation and nitrogen use efficiency of black soybean,and the nitrogen accumulation of black soybean was the highest under the MN level.Compared with CU,the nitrogen accumulation of black soybean under BU treatment significantly increased by9.98%-13.56%.Compared with CU,the NAE and PFP of black soybean under BU treatment increased by 17.47%-80.19%and 5.68%-18.69%,respectively.Through the analysis of comprehensive evaluation index method,it was found that winter wheat and black soybean had the highest scores under MN-BU treatment,which were 2.38 and 2.31,respectively.In summary,medium nitrogen application level(180 kg N hm^-2)blended controlled release urea and common urea with 1:1 can better meet the growth,yield and quality requirements of winter wheat and black soybean,and is conducive to sustainable agricultural production.It can be used as a suitable nitrogen fertilizer management plan for winter wheat-black soybean multiple cropping system in Guanzhong irrigation area.