Characteristics And Mechanisms Of N₂O Emissions And Nitrogen Leaching In Potato Field Under Different Irrigation Methods

In recent years,scholars at domestic and abroad have done some research on the effects of single irrigation method or single nitrogen application rate on soil N₂O emission and nitrogen leaching.However,the systematic study on N₂O emission and nitrogen leaching loss under drip,sprinkler and furrow fertilization needs to be further strengthened.Therefore,it is of great significance to explore ways to reduce N₂O emission,nitrogen leaching and ensure grain yield.In this study,the in-situ monitoring experiment was carried out in Hohhot potato farm from May 2018 to September 2019.The soil of potato field was taken as the research object,and different irrigation and fertilizer management methods were set up,they were DCK(drip irrigation+0kg N/ha),DD(drip irrigation+500kg N/ha),DG(drip irrigation+1000kg N/ha),SCK(sprinkler+0kg N/ha),SD(sprinkler+500kg N/ha),SG(sprinkler+1000kg N/ha),FCK(furrow irrigation+0kg N/ha),FD(drip irrigation+500kg N/ha)and FG(drip+1000kg N/ha).The characteristics of N₂O emission and nitrogen leaching under different water and fertilizer management modes were analyzed,the effects of different environmental factors on N₂O emission and nitrogen leaching were studied.It provides practical guidance for reasonable selection of one way of water and fertilizer management mode to improv water resources utilization efficiency and reduce N₂O emission and nitrogen leaching.The results are as follows:1.Soil N₂O emissions from potato fields in 2018 and 2019 have obvious seasonal variation characteristics,the peak of N₂O emission is concentrated in July and August.In the whole growing season of potato,the peak of N₂O emission was at flowering stage and tuber formation stage in 2018,and the peak of N₂O emission was mainly at flowering stage in 2019.In 2018,the cumulative N₂O emissions of DCK,DD and DG treatments at flowering and tuber forming stages accounted for 15%,25%,15%and 27%,41%and 42%respectively;the cumulative N₂O emissions of SCK,SD and SG treatments accounted for 32%,25%,38%and 31%,38%and 28%,respectively;the cumulative N₂O emissions of FCK,FD and FG treatments accounted for 34%,54%,37%and 40%,37%and 47%respectively.In 2019,the emission peak of each treatment mainly appears in the flowering period,with DCK,DD and DG accounting for 23%,33%and 39%respectively;SCK,SD and SG accounting for 33%,54%and 69%respectively;FCK,FD and FG accounting for 39%,52%and 55%respectively.During the whole growing season of potato,the cumulative emission of soil N₂O increased slowly at first,then increased,and then decreased gradually.2.The results of two-way ANOVA showed that different irrigation methods,nitrogen application rates and the interaction of irrigation methods and nitrogen application rates had significant effects on soil N₂O emission and nitrogen leaching(P<0.05).Under the same irrigation method and different nitrogen application rates,the cumulative N₂O emission of potato field increased with the increase of nitrogen application rate.Under the same nitrogen application rate and different irrigation methods.Compared with traditional furrow irrigation,drip irrigation and pipe sprinkler irrigation significantly reduced soil N₂O emission,which showed drip irrigation<pipe sprinkler irrigation<furrow irrigation.In 2018 and 2019,the cumulative emissions of N₂O from FCK,FD and FG soils were 2 kg/ha,23.79 kg/ha,45.73 kg/ha and 2.08 kg/ha,6.23 kg/ha and 13.93 kg/ha,respectively.DCK,DD and DG decreased by 35.00%,80.90%,75.60%and 26.70%,66.40%and 21.50%respectively,while SCK,SD and SG decreased by 13.46%,76.42%,81.13%and 18.50%,-92.76%and-86.72%respectively.In 2018 and 2019,the cumulative emission of N₂O from DD(drip irrigation and low fertilizer)soil was the lowest.3.Drip irrigation and pipe sprinkler irrigation can effectively reduce the N₂O emission intensity in 2018,and the N₂O emission intensity under different irrigation methods and the same nitrogen application rate in 2018 is significantly higher than that in 2019.The N₂O emission intensities of FCK,FD and FG were0.09kg N/t,0.61kg N/t and 1.17N/t,respectively.The emission intensities of DCK,DD and DG were reduced by 44.44%,86.89%and 83.76%respectively.The emission intensities of SCK,SD and SG were reduced by 33.33%,81.97%and 85.47%respectively.In 2019,drip irrigation can effectively reduce soil N₂O emission intensity.The N₂O emission intensity of FCK,FD and FG were 0.10kg N/t,0.18kg N/t and 0.39 N/t,respectively.While DCK,DD and DG are reduced by 40.00%,61.11%and 56.41%respectively.In 2018 and 2019,the N₂O emission coefficients of FD and FG were 4.36%,4.37%and 0.83%,1.19%respectively;DD and DG were 0.65%,0.99%and 0.45%,0.82%respectively;SD and SG were 0.70%,0.80%and 2.03%,2.42%respectively.In two years,the N₂O emission coefficient of DD(drip irrigation and low fertilizer)was the lowest.4.Under drip irrigation,sprinkler irrigation and furrow irrigation,soil N₂O emission flux was significantly positively correlated with soil water content(R²=0.76,0.94,0.83)and SOC(R²=0.83,0.79,0.81)(P<0.01),the amount of nitrogen leaching was significantly positively correlated with soil water content(P<0.001),and the amount of nitrogen leaching increased with the increase of soil water content.The correlation coefficients with soil water content were 0.77,0.85 and 0.76,respectively.The results showed that with the increase of soil N₂O emission,the nitrogen leaching loss also increased.Correlation analysis showed that there was a significant positive correlation between soil N₂O emission and nitrogen leaching(P<0.05),and the correlation coefficient was 0.83.5.The two-year field in-situ experiment showed that the dynamic change trend of nitrogen leaching loss was obvious under different irrigation methods in2018 and 2019,it was mainly in the form of nitrate nitrogen;the nitrogen leaching loss showed a downward trend with the increase of depth,and the inorganic nitrogen concentration and accumulated leaching amount at the depth of 80cm were lower than that at the depth of 40cm.Compared with traditional furrow irrigation,drip irrigation can effectively reduce the nitrogen leaching loss,and the nitrogen leaching amount decreases with the increase of depth.Compared with furrow irrigation,drip irrigation with the same nitrogen application rate in 2018 and 2019 can reduce the nitrogen leaching amount by36.95%?63.10%and 54.93%?87.92%in 40cm and 80cm,respectively.Under the same irrigation method and depth,the amount of nitrogen leaching increased with the increase of nitrogen application.The nitrogen leaching amount of FG₄₀(furrow irrigation with high fertilizer depth of 40 cm)was the highest,with the highest value of 53.29 kg/hm²,while that of DD₈₀(drip irrigation with low fertilizer depth of 80cm)was the lowest,with the lowest value of 3.43 kg/hm².6.The content of NO₂^-in soil leaching solution had an important impact on soil N₂O emission.The correlation analysis showed that the content of NO₂^-in soil leaching solution had a significant positive correlation with soil N₂O emission(P<0.05)DD(drip irrigation with low fertilizer)can increase grain yield and reduce N₂O emission,nitrogen leaching amounts,which is the best management measure for farmers.