| Manas River Basin is one of the important bases of cotton production in China,and it is also one of the important economic crop centers along the silk road.The ecological environment of Manas River Basin is of great significance to the local agricultural development.However,there are few studies on the characteristics and factors of greenhouse gas emissions under such agricultural conditions.This study uses static box meteorological chromatography method,which was carried out in May,August and October of 2019 The daily and monthly emission characteristics of CO2,CH4 and N2 O from cotton field in Manas River Basin were measured in April,and the spatial variation of different seasons was analyzed.The fluxes of CO2,CH4 and N2 O from cotton field in Manas River Basin were studied in combination with nitrogen application rate,water and heat characteristics,soil physical and chemical characteristics.The results show that: 1(1)The average values of soil CO2 fluxes in four regions(different nitrogen application levels)were greater than 0,and their average CO2 fluxes from large to small were A2(65hm2 · kg-1)> A3(70hm2 · kg-1)> A4(75hm2 · kg-1)>A1(60hm2 · kg-1)·The results showed that the soil of different nitrogen application levels were producing CO2;the CH4 emission flux of different nitrogen application levels was greater than 0,and the relationship of CH4 emission flux was A3(70hm2 · kg-1)> A4(75hm2 · kg-1)> A2(65hm2 · kg-1)> A1(60hm2 · kg-1)·The results showed that CH4 was produced in the soil of different nitrogen application levels,and the N2 O emission flux of different nitrogen application levels was greater than 0,and the relationship of N2 O emission flux was A4(75hm2 · kg-1)> A3(70hm2 · kg-1)> A2(65hm2 · kg-1)> A1(60hm2 · kg-1),which indicated that the soil of the sampling area was the "source" of N2 O.(2)The characteristic curve of CO2 emission in different seasons was high in August.The results showed that the average CO2 fluxes of soil in each month were greater than 0,which was the "source" of CO2 emission,and the average CO2 fluxes of soil in each nitrogen level area were August > may > October.In different months,soil CH4 fluxes varied greatly in different nitrogen application levels,but each region was the "source" of CH4 absorption in different months.The average CH4 emission fluxes in different regions were may > August >October.In different months,soil N2 O fluxes varied greatly in different nitrogen application levels,but each region was also the "source" of N2 O absorption in different months.The average N2 O emission fluxes in different regions were October > August > May.(3)Regression analysis was carried out on the average emission flux and the total daily emission of the best observation time,and the best observation time of9:00 was tested.The regression analysis showed that the correlation coefficient between the emission flux and the total daily emission of the three kinds of soil greenhouse gases at 9:00 was high,which indicated that the greenhouse gas emission flux at 9:00 was very close to the last sampling time of the day The average emission fluxes are relatively representative,which can be used as the best sampling time for the study of soil greenhouse gas emission fluxes at different nitrogen levels in the future.(4)There is no significant difference in GWP among A4,A3 and A2,but there is difference between them and A1.In the sampling in 2019,the soil of different nitrogen application levels in Mahe river basin is the "source" of greenhouse gas emissions,which means that it will have a positive impact on the greenhouse effect of Mahe River Basin.(5)The soil organic matter,ammonium nitrogen and nitrate nitrogen in different nitrogen application levels had obvious temporal changes,which showed a size relationship of August > may > October;the soil organic matter,ammonium nitrogen and nitrate nitrogen were in a very poor poor state,and the soil nutrient status was not ideal as a whole.The results showed that the soil temperature in A1,A2,A3 and A4 regions was August > may > October,and the monthly mean value was A1 > A3 > A2 > A4;the water content in soil showed the trend of October > may > August,and the order of each region was A4 > A3 >A1 > A2.(6)Soil organic matter,ammonium nitrogen,nitrate nitrogen and salt all have great effects on greenhouse gas emissions in different regions.Soil temperature,water content and nitrogen application rate have great direct and indirect effects on greenhouse gas emissions,but there is a great difference due to seasonal changes Different. |
