Research On Carbon Sequestration And Emission Reduction And Yield Increased In Spring Maize Based On The Long-term Conservation Tillage On The Loess Plateau

Under the background of global warming,the sustainable soil carbon sequestration and the soil greenhouse gas emissions reduction in agricultural production can help to increase the contribution of agricultural production to environmental protection and promote the green and sustainable development of agriculture.In the Weibei dryland region,farmers adopted conventional tillage to absorb the limited rainfall to increase soil moisture.But the loose and bare soil structure formed by long-term conventional tillage will not benefit storage water.In addition,long-term tillage causes serious damage to soil structure,aggregates broken and the full contact between soil carbon and air accelerates the mineralization of soil carbon,which leads to the decline of soil productivity and accelerates the emission of CO₂.The conservation tillage increased soil carbon sequestration but in long-term application will promote the soil carbon rich in surface layer and impact the vertical distribution character of soil carbon.Therefore,it is necessary to construct a reasonable and long-term applicable conservation rotational tillage system to overcome the disadvantages of single conservation tillage.A long-term site conservation tillage from2007 to 2020 about spring maize was conducted in Dry Farming Experiment Station,Northwest A&F University,Ganjin Town,Heyang County,Shaanxi Province,China.A single factor tillage random block design was adopted in the experiment with nine tillage practices:no-tillage/no-tillage/subsoiling(NNS),no-tillage/conventional-tillage/subsoiling(NCS),conventional tillage/conventional-tillage/subsoiling(CCS),no-tillage/subsoiling(NS),subsoiling/conventional tillage(SC),conventional tillage/no-tillage(CN),no-tillage(NT),subsoiling(ST)and conventional tillage(CT)was used as contrast.The soil physical properties,soil carbon pool properties,soil greenhouse emission,yield and water use efficiency were analysed to explore the effect of soil carbon sequestration,soil greenhouse emission reduction and yield increase,and got some results:(1)Soil bulk density(SB)and porosity was affected by different tillage.Compared with CT,NT and NNS increased SB by 7.8%and 10.0%in 0-10 cm soil depth,and long-term CT enhance SB in 20-30 cm soil depth,but NCS decreased SB and increased soil porosity in 0-40 cm,improve soil cultivate layers.NCS and NT increased>0.25 mm soil aggregate content and increased geometric mean diameter(GMD)by 3.4%and 10.4%.In0-40 cm soil depth,compared with CT,NCS significantly improved GMD by 23.3%,32.0%and 21.1%in 10-20cm,20-30cm and 30-40cm soil depth.NT significantly increased GMD in the 0-10cm soil layer by 18.4%.In the long-term planting of spring maize,the soil water storage insowing stage showed a fluctuating equilibrium state.(2)Soil carbon pool characteristics and carbon sequestration capacity of aggregates were significantly affected by tillage practice.NNS,NS and NT significantly increased the total organic carbon(TOC)content of 0-40 cm soil by 11.0%,23.0%and 10.8%,and at the same time,increased the easily oxidized organic carbon(EOC)content of soil.However,compared with CT,NNS,NS,NT and ST significantly increased the stratification rates of TOC in 0-10cm/10-20cm soil layers by 32.7%,10.9%,25.7%and 20.4%Increasing soil aggregates associated carbon was the main way to improve soil carbon sequestration,and NT significantly increased the carbon sequestration capacity of soil large aggregates by50.16%compared with CT.The increase of soil carbon pool turnover rate improved the soil carbon pool management index(CPMI).NCS and NS significantly increased the CPMI in0-40 cm soil depth by 35.9%and 37.5%compared with CT.(3)Conservation tillage significantly affected soil CO₂ and N₂O emission fluxes.Compared with CT,NNS,NCS,CCS,NS,SC,CN,NT and ST significantly reduced average annual soil CO₂ cumulative emission by 22.0%,22.8%,29.2%,48.8%,48.4%,57.8%,57.6%and 24.3%,respectively.Soil N₂O emission under NCS,NS,NT and ST treatments significantly decreased by 13.8%,10.4%,8.1%and 17.3%compared with CT,respectively.Compared with CT,NS significantly reduced the carbon footprint of agricultural production by 74.7%.Meanwhile,under conservation tillage,the global warming trend(GWP)caused by field gas emissions was inhibited,and CN and NT significantly reduced GWP by 54.3%and 55.7%.Combining agricultural production with ecological effects,NCS,NS,NT and ST significantly increased the carbon footprint and global warming trend at the yield scale.(4)The maximum and minimum average spring maize yield in experiment were9474.0 kg·hm^-2(NCS)but it was 8351.1 kg·hm^-2(CT).The results showed that the distribution type of rainfall at the growth stage significantly affected the yield of spring maize.Compared with the rainfall type B(rain occurred in the jointing-tasseling and drought in the filling-maturity),the type A(drought in the jointing-tasseling stage and rain in the filling-maturity stage)significantly increased the yield of spring maize.Under rainfall distribution type A,NNS,NS and ST significantly increased soil water storage at0-200 cm at jointing and tasseling stages,and increased spring maize yield by 10.6%,16.1%and 7.2%,compared with CT.Soil moisture and rainfall use efficiency were significantly affected by rainfall distribution and tillage practices.Compared with rainfall type A,rainfall type B significantly improved rainfall and soil water use efficiency.Under rainfall type A,CCS,NS and CN significantly increased WUE by 20.3%,15.5%and 19.1%compared with CT.CCS and NS significantly increased rainfall utilization efficiency by19.1%and 17.4%compared with CT.In the long-term experiment,NCS has the most obvious effect on soil water use efficiency and rainfall use efficiency,with annual average significantly increased by 22.6%and 11.9%compared with CT.In conclusion,conservation rotational tillage NCS can improve soil structure,regulate the vertical redistribution of organic carbon,increase the content and stability of soil aggregates,reduce soil greenhouse gas emissions and increase the ecological effect of agricultural production.Rainfall distribution during the growing season significantly affected maize yield.NNS and NT increased crop yield when rainfall distribution was uneven,but NCS had the most significant effect in long-term yield improvement.Therefore,based on the requirements of regulating vertical distribution of soil organic carbon,reducing greenhouse gas emissions and yield,NCS rotation tillage mode can be recommended as a long-term tillage mode applied in the Weibei arid highland and semi-arid regions with similar climate types.