Analysis On The Law And Influencing Factors Of NH₃ Volatilization And N₂O Emission In Peanut Field Of Red Soil Arid Hillside

Nitrogen is a limiting element in agricultural production.As a large agricultural country,China is the largest producer and consumer of nitrogen fertilizer in the world.The low efficiency of nitrogen fertilizer leads to a large amount of nitrogen loss,which mainly includes erosion loss,leakage loss and gaseous emissions.The gaseous nitrogen emissions represented by NH₃and N₂O easily lead to serious environmental risks or direct environmental pollution.Red soil hilly region in South China is an important grain and oil production area,in which peanut is one of the main oil crops.Due to improper cultivation and management measures,coupled with severe soil erosion on sloping farmland,the nutrient loss of dry slope land is very serious,which has become an important factor restricting the high-quality development of regional agriculture.At home and abroad,the research on the runoff and sediment reduction effect of soil and water conservation measures on sloping farmland is rather mature,and the research on their interception effect of non-point source pollution is gradually paid attention to,but less attention is paid to their reduction of nitrogen gaseous emission.In the paper,the typical red soil sloping land,planting peanut crops was selected as the research object.Five treatments including conventional tillage with hedgerow(CFP),conventional tillage with straw mulching(CFS),minimum tillage(NT),conventional tillage control(CF)and bare land control(LT)were set up,and each treatment was repeated 2-3 times.Through the monitoring of gaseous nitrogen(NH₃and N₂O)emissions in situ for two consecutive peanut growth seasons in 2019-2020,the temporal variation characteristics of gaseous nitrogen emission from peanut sloping land were analyzed,the differences of gaseous nitrogen emissions under different soil conservation measures were compared,and the key factors of gaseous nitrogen emission were identified.The main results were as follows:(1)Agricultural production was the main causes of gaseous nitrogen emission.The total loss of NH₃volatilization and N₂O emission in the whole peanut growing season was 8.91?18.52 and 0.29?0.56 kg N·hm^-2,accounted for 12.79%?19.49%and0.31%?0.57%of the total nitrogen application,respectively.NH₃volatilization and N₂O emissions caused by agricultural production accounted for 61.84%?68.41%and79.31%?82.14%of the total losses,respectively.(2)The hot spot period of NH₃was within 15 days after fertilizer,and the hot period of N₂O emission was within 20 days after fertilization.NH₃volatilization was the main way of gaseous nitrogen loss,accounting for 94.09%?98.64%of the total losses of the two kinds of gaseous nitrogen.(3)Different soil and water conservation measures affected the gaseous nitrogen emissions by changing soil properties.Compared with conventional tillage(CF),conventional tillage with hedgerow(CFP),conventional tillage with straw mulching(CFS)and light simplified no-tillage(NT)decreased the cumulative NH₃volatilization by17.73%?19.82%,13.46%?27.27%and 7.07%?23.22%,respectively,and increased or decreased the cumulative N₂O emission by 37.50%?89.66%,-3.37%?37.50%and7.41%?55.17%,respectively.(4)Based on the enhanced regression tree(BRT)analysis,it was found that soil ammonium content,days after fertilization,fertilization period,tillage measures,soil nitrate content,soil water content,air temperature and soil temperature were the key influencing factors of ammonia volatilization,and their contribution rates were 33.40%,14.10%,12.10%,6.80%,6.20%,5.70%,5.30%and 5.10%respectively.The key influencing factors and contribution rate of N₂O emission were as follows:soil water content(27.40%),days after fertilization(13.60%),soil nitrate nitrogen content(11.60%),rainfall in the first 2 days(8.70%),rainfall in the first 3 days(7.20%),soil temperature(6.80%),soil ammonium nitrogen content(6.00%),air temperature(5.10%)and tillage measures(5.00%).These results can provide theoretical basis and technical options for reducing gaseous nitrogen loss,improving nitrogen use efficiency and reducing environmental pollution in slope agriculture of red soil hilly region in South China.