N₂O Emission And Nitrogen Utilization Of Spring Maize Under Different Nitrogen Management Models In The Loess Plateau

As the main driving factor of global climate change,the increase in greenhouse gas content has become one of the issues that countries generally pay attention to.Nitrous oxide is one of the three main greenhouse gases（N₂O,CH₄ and CO₂）in the atmosphere,and N₂O emissions from agricultural sources account for 60%of the total global emissions.The area of dry farmland in China accounts for about 70%of the total land area,of which the area of arid and semi-arid farmland accounts for about 43%of the total farmland area.As one of the main grain producing areas in China,the farmland of the Loess Plateau has problems such as high nitrogen usage and low nitrogen utilization rate.Therefore,exploring the relationship among spring maize yield,N₂O emission and nitrogen utilization in the district under different nitrogen management modes has important practical significance for the district’s agricultural development and environmental protection.The experimental research site is located in the loess arid plateau area in the southern Loess Plateau,and five nitrogen management modes are set up in the experiment:No nitrogen（CK）,traditional nitrogen application(N250,N 250kg?hm^-2),reduced nitrogen application(N200,N 200kg?hm^-2),reduced nitrogen application+slow controlled release fertilizer(N200+SR,N 200kg?hm^-2)and reduced nitrogen application+nitrification inhibitor(N200+DCD,N 200kg?hm^-2).The yield,N2O gas emission and nitrate nitrogen content of spring maize during harvest period were measured respectively.The main conclusions are as follows:（1）Nitrogen application can significantly increase spring maize yield,but it is more cost-effective to reduce nitrogen application appropriately.Compared with N250treatment,the yield of spring corn in N200,N200+SR and N200+DCD treatments did not decrease significantly.However,the partial productivity of nitrogen fertilizer increased by 32.3%,32.3%,and 28.6%,and the physiological utilization rate of nitrogen fertilizer increased by 40.7%,46.7,and 43.2%,respectively.The output of each treatment is between 3197.5-13869.9 kg·hm^-2（2019）and 3861.6～9987.0kg·hm^-2（2020）.At the same time,nitrogen application can significantly increase the above-ground biomass of spring maize,but there is no significant difference in above-ground biomass between different nitrogen application treatments.（2）Reduced nitrogen application can significantly reduce the accumulation of nitrate nitrogen in different soil layers of spring maize.The accumulation of nitrate nitrogen in the soil layers of 0-100cm,100-200cm,and 200-300cm in each treatment ranged from 19.5-82.8 kg·hm^-2,5.7-25.9 kg·hm^-2 and 5.7-24.7 kg·hm^-2.Compared with N250,N200,N200+SR and N200+DCD treatments significantly reduced the accumulation of nitrate nitrogen in the 0-300cm soil layer by 55.8%,69.3%and 62.8,respectively.（3）Reduced nitrogen application can significantly reduce N₂O emissions,and the effect of combined application of slow-release urea and nitrification inhibitor is better.N200,N200+SR and N200+DCD treatments can significantly reduce the cumulative emission of N2O.Compared with the cumulative emissions of N250treatment,the cumulative emissions of N200+DCD treatment reduced the most（33.3%）,and the cumulative emissions of N200 treatment reduced the least（20.5%）.N2O emissions have a strong response to nitrogen application and rainfall.The cumulative emissions within 10 days after rainfall account for 18.9%（2019）and 22.5%（2020）of the cumulative emissions of the entire growing season.