Effects Of Deficit Irrigation On Soil CO₂ And N₂O Emissions From Winter Wheat-summer Maize Rotation Fields

Irrigation can affect the production and emission of greenhouse gases by affecting the life activities of the microorganisms in soils and the root growth of crops.Most of the studies on soil-greenhouse gases in water-saving irrigation were concentrated in paddy fields and cotton fields and were less involved in the winter wheat-summer corn rotation system.In this study,different irrigation levels were set to study the effects of deficit irrigation on soil CO₂ and N₂O emission characteristics in winter wheat-summer corn rotation fields,and to explore the effects of environmental factors such as soil moisture,soil temperature,and soil nitrogen on CO₂ and N₂O emissions.In order to optimize irrigation management measures and provide scientific basis and theoretical support for water conservation in farmland.The winter wheat variety was “Xiaoyan 22”,and the summer corn variety was “Jinbei 288”.The experiment was carried out by using the method of static chamber/gas chromatography in situ observation of soil greenhouse gas emissions emission from summer maize under the transform of farmland moisture proving ground of China academy of the water-saving agriculture in arid of Northwest A & F University in from October 2015 to October 2016.Five treatments were set up in the experiment,namely CK,T1,T2,T3 and T7.CK was fully irrigated.The amount of irrigated water was measured by evaporative evapotranspiration ET.Other irrigation levels were depleted in a certain proportion on the basis of CK treatment,the winter wheat dehydration growth period for the wintering period and the jointing to the filling period,the summer corn dehydration growth period from sowing to jointing and jointing to tasselling period,in the two crop water deficit growth period,T1 water deficit 20%,T2 water deficit 40%,T3 was depleted 20% in the first depletion period and was fully irrigated during the second deficient growth period,T7 was depleted 40% in the first depletion period and depleted 20% during the second deficient growth period.The results were as follows:1.The CO₂ and N₂O emission of farmland soil under winter wheat-summer maize rotation system has obvious seasonal variation.The highest value occurred in the summer,the spring and autumn were relatively low,and the winter was kept at the lowest level.The seasonal fluctuations of soil CO₂ and N₂O emissions during the winter wheat and summer maize growth seasons were relatively large,and the treatment trends under the deficit irrigation were basically the same.The main peak of winter wheat emission occurred from the jointing stage to the grain filling stage,the secondary peak appeared at the seedling stage,and it was at a lower level in winter.There were three emission peaks during the growth period of summer maize.The main peak of emission occurred from jointing to tasselling,and the secondary peak occurred from sowing to jointing,and it was at a low level from tasseling to maturity.2.Deficit irrigation had a certain influence on the average emission of soil CO₂ during the growing season under the winter wheat-summer corn rotation system.During the different growth stages of winter wheat-summer corn,the average flux of CO₂ in soil was basically CK>T3>T1>T7>T2.During the winter wheat growth period,the average CO₂ flux of soil showed the following stages: jointing-grouting stage> seedling stage> grouting-maturity stage> turning green-jointing stage> wintering stage,and the average N₂O flux of the soil showed: seedling stage> jointing-grouting stage>wintering stage>growing-mature stage>turning green-jointing stage.The average fluxes of CO₂ and N₂O in different treatments during the growth stage of summer maize were from sowing to jointing stage>jointing stage to tasselling stage>pumping to maturity stage.3.Deficit irrigation has certain effects on cumulative CO₂ and N₂O emissions under winter wheat-summer corn rotation system.In the whole growing season of winter wheat-summer corn,the CK treatment was the largest.The accumulated CO₂ and N₂O emission from the treated soil increased gradually during the growth period of winter wheat and summer maize.In the wheat season,the cumulative rate of cumulative CO₂ emission in the soil was low at the seedling stage and wintering stage,gradually increased during the turning green-jointing stage,and reached the maximum at the jointing-filling stage,and entered the stage of grouting-maturity,and then decreased.The cumulative rate of N₂O accumulation in soil was relatively high at the seedling stage,decreased during the overwintering period,gradually increased during the regreening-jointing stage,reached the maximum during the jointing-grouting stage,and entered the stage of grouting-maturity,and declined again.In the maize season: The cumulative CO₂ emission from soil increased slowly at the sowing-jointing stage,entered the jointing stage,and then increased,and decreased again during the tasseling-mature stage.At the sowing-jointing stage,the cumulative N₂O emission from all treatments increased relatively quickly.At the jointing stage,the cumulative N₂O emission rate of the soil has a slowing trend,and it has decreased at the tasseling-mature stage.4.There was a positive correlation between soil CO₂ emission flux and WFPS in the winter wheat-summer corn rotation field under deficit irrigation.With the exception of T1 and T7 treatments,the correlations of other treatments reached a significant level?P<0.05?.There was no significant difference between the correlation coefficient of soil CO₂ flux with 0-10 cm soil layer and the correlation coefficient of 10-20 cm soil layer.There was a positive correlation between soil CO₂ flux and soil 5 cm,10 cm,15 cm,20 cm,and 25 cm soil,and the correlations reached extremely significant levels?P<0.01?,the correlation coefficient between 15 cm and 20 cm were higher among them.5.There was a positive correlation between soil N₂O fluxes and 0-10 cm and 10-20 cm WFPS in winter wheat-summer maize rotations under deficit irrigation,and the correlations reached extremely significant levels?P<0.01?.In addition to T1 treatment,the correlation coefficient between soil N₂O flux and 10-20 cm soil layer was larger than that of 0-10 cm soil layer.There was a positive correlation between soil N₂O flux and soil 5 cm,10 cm,15 cm,20 cm and 25 cm soil?P>0.05?.There was a positive correlation between soil N₂O flux and soil nitrate N,and There was a negative correlation between ammonium nitrogen in soil and the correlations did not reach significant levels?P>0.05?.