Effects Of Long-Term Different Nitrogen Management Practices On Yield And Soil Organic Nitrogen Components Of Rain-Fed Spring Maize Under Film Mulching

In order to investigate the effects of nitrogen fertilizer and organic fertilizer application on the yield and organic nitrogen fraction of spring maize in dry crop mulching on the Loess Plateau in northwest China,this study was based on the experiment of different nitrogen fertilizer application on spring maize(Xianyu 335)at the National Agro-ecological Experiment Station of Loess Plateau in Changwu in 2010(there were 8 treatments,FN0:plastic film mulching+no nitrogen application,FN100: plastic film mulching+100kg/ha,FN250: film mulching+nitrogen application 250kg/ha,FN400: film mulching+nitrogen application 400kg/ha,N0: film mulching+nitrogen application,N100: film mulching+nitrogen application 100kg/ha,N250: film mulching+nitrogen application 250kg/ha,N400: film mulching+nitrogen application 400).According to Bremner’s organic nitrogen classification method,the composition of soil organic nitrogen,soil total nitrogen,nitrogen accumulation in different organs of maize plants and maize yield after harvesting in 2021 and 2022 were measured and analyzed.The main results of this study are as follows:(1)Positioning tests with different N fertilizer dosages showed that within a certain range,yield increased with increasing N fertilizer dosage and yield did not increase further with excessive N application,and the highest yield was achieved in the FN250 treatment with 279%(2021)and 249%(2022)increase in yield compared to the FN0 treatment,and the yield of the high N treatment FN400 was not significantly different from the FN250 treatment.The dry matter accumulation at harvest,nitrogen accumulation before and after flowering,and nitrogen transfer from stems and leaves were better in the 250 kg/ha N application treatment under mulching conditions.(2)Organic fertilizer application significantly increased spring maize grain yield,dry matter accumulation and nitrogen accumulation.Compared with N treatment,the yield of NM treatment increased by 8.3%(2021)and 28.5%(2022).Compared with N treatment,the dry matter accumulation of NM treatment during harvest increased by 42.3%(2021)and 20.8%(2022).The pre-flowering nitrogen accumulation increased by 32.1%(2021)and 6.8%(2022)compared with the N treatment,and the post-flower nitrogen accumulation increased by 12.4%(2021)and 23.5%(2022)compared with the N treatment.(3)The location experiment of different nitrogen application rates showed that the contents of soil total nitrogen,acidolysis total organic nitrogen,acidolysis ammonia nitrogen,amino acid nitrogen,amino sugar nitrogen and unknown nitrogen would increase with the increase of nitrogen application rate.The optimized aggregated boosted trees(ABT)analysis showed that in 0～10cm soil layer,amino acid nitrogen(40.06%)and acid hydrolysis ammonia nitrogen(21.77%)were the most important factors contributing to the yield.(4)The application of organic manure can increase the contents of soil total nitrogen,acidolysis total organic nitrogen,acidolysis ammonia nitrogen,amino acid nitrogen,amino sugar nitrogen and unknown nitrogen,but there is no significant difference in the proportion of organic nitrogen components to soil total nitrogen.The optimized aggregated boosted trees(ABT)analysis showed that the acidolysis ammonia nitrogen and amino acid nitrogen were the most important factors contributing to the yield in the topsoil(0～20cm).