Effect Of Nitrogen Regulation On The Loss Of Active Nitrogen In Spring Maize Field In Northeast Black Soil

Unreasonable application of nitrogen fertilizer aggravates the loss of active nitrogen in farmland,which leads to environmental pollution problems such as massive emission of greenhouse gases,eutrophication of water body and excessive nitrate in groundwater.In order to analyze the effect of nitrogen control measures on the loss of active nitrogen in spring maize fields in northeast black soil,a field experiment was conducted in Lishu County,Jilin Province from 2019 to 2020..Six treatments were set up:no nitrogen control（NO）,conventional nitrogen application(N_Conv),optimized fertilization(N_OPT),controlled release nitrogen fertilizer(N_Ctrl),increased application of organic fertilizer（FM）and straw returning（SR）.The aeration method and static chamber-gas chromatography were used to monitor ammonia（NH₃）volatilization and nitrous oxide（N₂O）emission dynamics in the field,and determine that nitrate nitrogen content of 0-100 cm soil in the mature period of corn,and the effects of nitrogen fertilizer regulation and organic materials application on the gaseous loss of active nitrogen and the residual nitrate nitrogen in the soil of spring maize fields in the black soil of Northeast China were studied.In order to provide theoretical basis for formulating green nitrogen management measures for increasing yield and increasing efficiency of spring maize in black soil of Northeast China.The main conclusions are as follows:1.Compared with N0,N_Conv,N_OPT,N_Ctrl,FM and SR obviously raising corn output.In 2019,the yield of each treatment ranged from 9770 kg hm^-2 to 11742 kg hm^-2.In 2019,the yield of each treatment ranged from 9770 kg hm^-2 to 11742 kg hm^-2.Compared with N_Conv treatment,FM treatment significantly increased the corn yield by 10.3%.The yield range of each treatment in 2020 is 9114 kg hm^-2～14388 kg hm^-2.Compared with N_Conv,FM treatment significantly increased corn yield by 28.8%.SR treatment also increased corn yield,but did not reach a significant level,with an increase of 15.5%.In 2019,compared with N_Conv,N_OPT,N_Ctrl,FM and SR all improved nitrogen use efficiency to a certain extent,with the increase rates of 9.2%,3.8%,39.7%and 25%,respectively.In 2020,compared with N_Conv treatment,N_OPTtreatment,N_Ctrl treatment,FM treatment,and SR treatment significantly improved the nitrogen use efficiency,with the increase rate of 35.2%,31%,53.8%and 38.1%,respectively.From 2019 to 2020,the grand total of nitrate nitrogen in 0-100 cm soil profile decreased gradually with the deepening of soil depth.The grand total of nitrate nitrogen in 0-100 cm soil profile of SR process was obviously higher than that of other measures,and the grand total of nitrate nitrogen in 0-20 cm soil layer was the highest,reaching 16.5 kg·hm^-2（2019）and 29.3 kg·hm^-2（2020）.2.Compared with N0,nitrogen fertilizer application promoted ammonia volatilization.The ammonia volatilization rates of N_Conv,N_OPT and FM reached the peak on the 2nd to 3rd day after fertilization,which were 2.9 kg·hm^-2 d-¹,3.2 kg·hm^-2d^-1 and 3.1 kg·hm^-2·d^-1 respectively（two years）Because N_Ctrl and SR are mixed with slow and controlled release fertilizer,the release rate of fertilizer nutrients is slow,and the peak value of ammonia volatilization is 2.8 kg·hm^-2·d^-1 and 2.9 kg·hm^-2·d^-1,respectively.The two-year average ammonia volatilization rates of N0,N_Conv,N_OPT,N_Ctrl,FM and SR treatments were 0.56,0.65,0.65,0.62,0.71 and 0.59 kg·hm^-2·d^-1.The accumulation of ammonia volatilization caused by topdressing in N_OPT and FM treatments were significantly higher than that in other treatments due to the simultaneous rain and heat during topdressing,while the total amount of ammonia volatilization between N_Conv,N_OPT and N_Ctrl treatments did not reach a significant level.The average ammonia volatilization accumulation of each treatment in two years was 23.5～34.0 kg·hm^-2.Compared with N_Conv,N_Ctrl and SR,N_OPT and FM significantly increased the ammonia volatilization accumulation,reaching 3.2%and4.2%of the nitrogen fertilizer application respectively.Correlation analysis shows that the volatilization rate of NH₃ was positively correlated with soil temperature,soil water content,NH₄⁺-N and NO₃^--N contents.3.Nitrogen application can significantly increase N₂O emission.The N₂O emission flux was 25.2～80.1μg N₂O-N m^-2h^-1 in 2019 and 30.5～103.8μg N₂O-N m^-2h^-1 in 2020.The peak value of N₂O emission generally occurs 3-5 days after fertilization or rainfall.In 2019,compared with N_Conv treatment,FM and SR treatment significantly increased N₂O cumulative emissions and N₂O emissions per unit yield;In 2020,compared with N_Conv treatment,SR treatment significantly increased N₂O emissions and N₂O emissions per unit yield.Compared with N_Conv treatment,FM treatment significantly increased the total amount of N₂O emission,but there was no significant difference in N₂O emission per unit yield compared with N_Conv treatment.Compared with N_Conv treatment,N_OPT and N_Ctrl treatment significantly reduced N₂O emissions and N₂O emissions per unit yield.Correlation analysis shows that N₂O emission rate is positively correlated with soil water content NH₄⁺-N and NO₃^--N,but negatively correlated with soil temperature.To sum up,under the condition of reduced nitrogen application,ordinary urea mixed with 30%controlled-release urea can achieve stable yield and significantly improve nitrogen use efficiency,while reducing nitrate nitrogen residue,and effectively reduce NH₃ volatilization and N₂O emission loss.With the development of national black land protection action,straw returning is an inevitable trend of future agricultural development.Under the condition of straw returning,mixing common urea with controlled-release nitrogen fertilizer in a certain proportion and then applying it at one time is an effective control measure to increase yield and increase efficiency of spring corn in black soil of Northeast China.