The Rules And Regulation Of Farmland Carbon Cycle Under Conservational Tillage

By the study object of the representative farmland doubled cropped with wheat andmaize in Huang Huai Hai Plain, and with the main technique subject of production underdifferent quantity of straw returned and conventional tillage, the experiment was carried outfrom2010-2012. To explore the rules and regulation of carbon cycle in conventional tillagefarmland that doubled cropped with wheat and maize, and provide the basis for conservationtillage technology popularization and application, the experiments studied the laws of soilspatio-temporal variation on soil carbon cycle, greenhouse gases emission, and the effects ofthe carbon cycle under different the amount of crop straw returned. As the main component ofgreenhouse gases, for realizing the goal of low carbon agriculture and agricultural sustainabledevelopment, it is important to research the rules of carbon cycle and regulation further. Themain results were as follows:1Rules of soil carbon sequestration and regulation under conservational tillagefarmlandUnder the whole straw returned, soil organic carbon, total nitrogen content increased andsoil bulk density decreased in conservational tillage farmland. Soil organic carbon increasedsignificantly compared with the original way in the transformed tillage farmland, and itincreased4.0%or more in the farmland changed from Zero tillage to subsoil tillage. Soilorganic carbon and total nitrogen increased higher with the increased quantity of corn strawreturned. Straw returned and the cultivation transformation can reduce soil bulk density, and itdecreased about0.5g· cm-3average one year.Under different conservational tillage, carbon nitrogen ratio in0-20cm soil layerincreased average1.02one year, and it increased1.26in tillage convension farmland. Thecarbon nitrogen ratio increased higher with the increased quantity of corn straw returned.Subsoil tillage has the strongest ability of carbon sequestration. The modes of tillagetransformed and the straw returned were all enhanced the amount of soil carbon sequestration.The annual average quantity of soil carbon sequestration increased significantly under themodes of zero tillage changed to subsoil tillage. 2Rules and regulation of carbon sequestration on crop in conservational tillagefarmlandCrop yield in subsoil tillage farmland was highest. The yield was increased1.03%higherin conventional tillage farmland than it in zero tillage. The crop yield was increased2.9%everyear after the tillage transformed. It was to be benefit of the crop yield by convension tillage.Under straw present farmland, the crop yield was increased significantly than straw returnedpartly.In conservation tillage farmland, the amount of crop carbon sequestration was higher thanconventional tillage, and it in the subsoil tillage was highest. The modes of tillage conversionand the quantity increased of straw returned were both benefit of crop carbon sequestration.3Rules and influence factors on soil respiration in conservational tillage farmlandIn conservational tillage farmland, the speed ratio of soil respiration in wheat growthseason was higher meanly5.8times than it in maize. In wheat period, during daytime, thespeed ratio of soil respiration was1.1-1.15times higher than it in night in wheat season, and itwas1.93times higher in maize season than it in wheat season. The soil respiration washighest in conventional tillage farmland, but it was lowest in zero. The trend of soilrespiration reduced after the tillage changed, except zero tillage.Soil respiration was significantly positive correlation with the quantity of straw returned,and it was the same correlation with soil organic carbon content. Soil respiration was positivecorrelation with soil moisture.In conservational tillage farmland, the annual amount of carbon emission on soilrespiration was lower mean1.3t/hm²than conventional tillage. After transformation ofcultivation, the range of soil respiration increased or decreased about1.5%compared with theoriginal way. The pattern of straw returned could change the carbon emission of soilrespiration. Soil respiration in conventional tillage and straw present farmland was1.11timeshigher than straw absent.4Effects of carbon cycle on production inputs in conservational tillage farmlandThe annual production carbon inputs were smaller difference in different tillage farmland,it was less than2.5%difference in each tillage farmland. In wheat growth period, themachinery carbon emissions of conventional tillage were maximum, except subsoil tillage.The machinery carbon emissions in maize season were only account for75.8%in wheat. Thewheat inputs of production means was approach to maize.The fertilizer inputs was above thehalf of total inputs.The mean production profit of maize was1.14times than wheat. The benefit of subsoiltillage was20691.4Yuan/hm², and it was the highest benefit way in whole year. The benefit ofcrop production on conservational tillage was higher than it on conventional. Compared with conservational tillage, the production carbon inputs was non-significantdifference than conventional tillage, but carbon emission of machinery. The economicbenefits of conservational tillage was significant different from conventional tillage.5Rules and influence factors on emission of greenhouse gases in conservational tillagefarmland5.1Rules and influence factors on emission of CH₄In conservation tillage farmland, CH₄was absorbed from atmosphere, the uptake washigher in summer, and lower in winter; The CH₄absorption flux in maize growth season was4⁵times higher than it in wheat season. CH₄absorption flux in conservation tillage farmlandwas smaller than it inconventional tillage. Straw returned could reduce the CH₄uptake flux.Tillage transformation increased CH₄absorption, but the increment of it was less than2%.The CH₄uptake flux was mainly related with farming modes, quantity of straw returned,etc. CH₄absorption fluxes in conventional tillage was8.65%higher than the correspondingzero tillage treatment. The absorption of CH₄flux was significant positive correlation with thesoil surface temperature, was negatively related to the soil moisture, and was significantlypositive correlation with soil organic carbon.5.2Rules and influence factors on N₂O emissionsN₂O emission has obvious seasonal variation in conservation tillage farmland. N₂Oemissions, and it in daytime was high, the night was low. N₂O emissions rise along with theadd of temperature. N₂O emission flux in corn season was higher than wheat.The annual CH₄uptake flux in conventional tillage farmland was10.5%higher thanconservation tillage. CH₄uptake flux increased slightly under tillage mode shift, by anaverage of4.34%in one year. The annual CH₄uptake flux in straw present farmlanddecreased about12.7%than straw absent.The annual N₂O emissions flux in Conventional tillage farmland was2.3%lower thanconservation tillage. N₂O emissions flux increased an average of2.27%slightly under tillagemodes shift. The annual N₂O emission under straw present was higher8.1%than straw absent.5.3Rules and influence factors on CO₂emissionsIn conservation tillage farmland, CO₂emission in corn season was2.1times higher thanin wheat. Compared with original farming methods, the CO₂emissions reduced after farmingtransformation. With the amount of straw returned increased, the CO₂emissions increased;CO₂emission was significant correlation with atmospheric temperature.The average annual CO₂emissions under conventional tillage was higher2.43tCO₂·hm^-2· a^-1than conservation tillage. After Farming transformation, CO₂emissions reduce 0.93tCO₂·hm^-2·a^-1than original farming methods. Straw present increased farmland’s CO₂emissions, and it was14.4%higher than straw absent.Throughout the year, in conservation tillage farmland, the total greenhouse effects ofCO₂accounted for97.4%of the total greenhouse effect, and N₂O occupied2.88%, and theabsorption of CH₄was only0.27.To reduce farmland greenhouse effect of greenhouse gases,we should primarily reduce CO₂emissions. The reasonable amount of straw returned and thetillage conversion can reduce the greenhouse effect in farmland.6Determination of the way on different height corn straw returnedThe energy value of Maize straw at the straw bottom is the highest, and the mainnutrients at the top is the highest. Evaluating from comprehensive utilization of maize straw,we think the way of0.5m stubble returned is reasonable.7The carbon cycle laws and carbon efficiency in Conservation tillage farmland7.1The carbon efficiency in Conservation tillage farmlandThe carbon efficiency in subsoil tillage farmland was highest, and the zero tillage waslowest. The modes of tillage transformed and the quantity of straw returned improved thecarbon efficiency Significantly. The carbon efficiency of maize was higher than wheat.7.2The carbon cycle laws in Conservation tillage farmlandAmong the conservation tillage farmland ecological system, the amount of annual netcarbon fixed in subsoil tillage farmland was5.801tCE/hm², and it was the maximum tillage.The lowest mode was conventional tillage, and it was less2.199tCE/hm²than subsoil. Thefixed carbon content in zero tillage changed farmland was improved22.96%one year. Strawreturning not enhanced the net amount carbon fixed Significantly, and it was not a linearrelationship with quantity of straw returned. The way of0.5m straw returned is better toimprove carbon fixation.In the carbon cycle of farmland ecosystem, carbon emissions of soil respiration accountfor40.66%in annual total carbon emissions, production inputs was4.11%, CH₄uptake offarmland accounts for0.1%, crop fixed carbon was55.13%, and carbon sequestration in soilaccounting for4.97%. To reduce carbon emissions, we should reduce the amount of soilrespiration mainly, and increase crop carbon fixation. Conservation tillage and thetransformation of cultivation can improve net amount of carbon sequestration.7.3Carbon ecological footprint in conservation tillage farmlandCarbon ecological surplus in subsoil farmland was the highest, and conventional was thelowest, it account for55.8%of subsoil. Transformation of cultivation significantly increasedcarbon ecological surplus: carbon ecological surplus increased by16.6%under zero tillage changed. Carbon ecological surplus is not a proportional relationship with the amount ofstraw returned. The carbon ecological surplus by0.5meters way of straw returned is thelargest.Above all, as an alternative to conventional tillage, both on theoretical aspect, and on theproduction practice technique, conservational tillage technology has feasibility of carbonemission reduction. Conversion tillage and appropriate amount of straw returned are effectiveway to increase carbon sequestration in farmland, and it will be realized low carbonproduction.