Effects Of Different Nitrogen Fertilizer Types On Nitrogen Footprint And Nitrogen Utilization Efficiency Of Rice And Rapeseed Planting Mode

The rice and reapseed planting mode is one of the most common multiple cropping modes in China.The traditional rice and reapseed planting mode is usually inseparable from a large amount of chemical fertilizers and pesticides.It not only has a low nitrogen utilization rate,but also causes a large amount of nitrogen loss,and brings a series of serious environmental problems.Therefore,this study conducted a field experiment at Huazhong Agricultural University in Wuhan,Hubei Province from 2021-2022 to explore the effects of different nitrogen fertilizer types on the nitrogen footprint and nitrogen fertilizer utilization efficiency of the rice and reapseed planting mode,aiming at screening nitrogen fertilizer types with high nitrogen efficiency.Huayouza No.9 and 19 Xiang were selected as the test materials,and five treatments were set up:（1）no nitrogen fertilizer（CK）,（2）urea（UF）,（3）slow-release fertilizer（SF）,（4）biochar+urea（BF）,（5）urea+nitrification inhibitor+urease inhibitor（DF）.The main findings are as follows:1.Different nitrogen fertilizer treatments significantly increased the content of soil available nitrogen in the rice and reapseed planting model.In the rape season,compared with CK,the NH₄⁺-N content in UF,SF,DF,and BF soils increased 0.9,1.2,1.0,and 0.9times,respectively,and the NO₃^--N content in soil increased 2.8,3.2,2.9,and 2.8 times,respectively.In the rice season,compared with CK,the content of NH₄⁺-N in UF,SF,DF and BF soils increased 2.8,2.9,2.8 and 2.9 times respectively,and the content of NO₃^--N in soils increased 0.8,1.0,0.7 and 0.8 times respectively.Compared with UF,SF,DF and BF significantly increased the content of soil available nitrogen in the middle and late stages of crop growth.2.Different nitrogen fertilizer treatments significantly affected the nitrogen footprint in the rice and reapseed planting mode.The nitrogen footprint under different treatments in rape and rice seasons was 4.51～8.73 g N-eq kg^-1 yr^-1和1.71～3.13 g N-eq kg^-1 yr^-1,respectively.SF,DF and BF significantly reduced the active nitrogen loss and nitrogen footprint compared with UF.In the rape season,compared with UF,the loss of active nitrogen of SF,DF and BF decreased by 27.0%,31.6%and 23.3%respectively,and the nitrogen footprint decreased by 31.6%,33.5%and 26.5%respectively.In the rice season,compared with UF,the loss of active nitrogen of SF,DF and BF decreased by 12.1%,7.0%and 32.6%respectively,and the nitrogen footprint decreased by 35.5%,18.2%and 45.4%respectively.3.Different nitrogen fertilizer treatments significantly improved the nitrogen utilization efficiency of crops in the rice and reapseed planting mode.In the rape season,compared with UF,the agronomic utilization efficiency of SF,DF and BF increased by21.2%,8.8%and 13.6%respectively,the absorption utilization efficiency increased by27.9%,10.3%and 19.3%respectively,and the physiological utilization efficiency increased by 70.2%,10.3%and 34.5%respectively.In the rice season,compared with UF,the agronomic utilization efficiency of SF,DF and BF increased by 126.8%,48.5%and81.0%respectively,the absorption and utilization efficiency increased by 49.3%,32.8%and 41.5%respectively,and the physiological utilization efficiency increased by 28.8%,13.5%and 17.6%respectively.4.Different nitrogen fertilizer treatments significantly improved crop yield and economic benefits in the rice and reapseed planting mode.In rape season,compared with CK,the yield of UF,SF,DF and BF increased by 46.8%,56.7%,50.9%and 53.1%respectively,and the economic benefit increased by 1.2,1.8 and 1.1 times respectively.In the rice season,compared with CK,the yield of UF,SF,DF and BF increased by 40.7%,92.3%,60.4%and 73.6%respectively,and the economic benefit increased by 0.7,1.9,1.1and 0.7 times respectively.To sum up,compared to single urea treatment,slow-release fertilizer,biochar and biochemical inhibitor treatment significantly improved the content of soil available nitrogen and nitrogen fertilizer utilization efficiency in the middle and late stages of crop growth,reduced the loss of active nitrogen and nitrogen footprint,and increased the yield and economic benefits,all of which belong to high-efficiency nitrogen fertilizer.Comprehensively,slow-release fertilizer has the best effect.