【作者】 王丙文；

【导师】 李增嘉； 宁堂原；

【作者基本信息】 山东农业大学 ， 农业生态学， 2013， 博士

【摘要】 本试验于2010-2012年间以我国最具代表性的黄淮海平原小麦－玉米一年两熟农田为研究对象，以小麦、玉米两作一体化秸秆不同还田量和保护性耕作生产为技术主体，研究保护性耕作条件下的农田土壤碳循环时空变化规律，农田温室气体的时空排放规律,农作物秸秆还田量调节对农田碳循环的影响、作物生产动力消耗规律与生产投入经济适性；以期探寻在麦-玉两熟保护性耕作措施下的农田碳循环规律与调控研究，为麦-玉两熟保护性耕作技术体系推广应用提供依据。碳元素作为温室气体的主要组成元素，进一步研究农田碳元素的循环规律和调控，对实现低碳农业目标和农业可持续发展都具有重要意义。主要研究结果如下：1保护性耕作农田土壤固碳规律及调控秸秆全量还田下，保护性耕作农田土壤的有机碳、全氮含量增加，土壤容重降低。转变耕作方式后，土壤有机碳与原方式相比显著增加，其中免耕转变为深松后增幅达4.0%以上。随玉米秸秆还田量的增加，土壤有机碳和全氮提高的幅度越大。秸秆还田和转变耕作方式都能降低土壤容重，年均降低约0.5g· cm^-3。保护性耕作的农田，年度0-20cm土层碳氮比平均增幅为1.02,转变耕作方式后年均提高碳氮比1.26。增加秸秆还田量可以提高土壤的碳氮比。保护性耕作农田，深松耕作具有最强的固碳能力。转变耕作方式和增加秸秆还田量，都能增加土壤固碳量。免耕转深松后年固碳增加效果极显著。2保护性耕作农田作物的固碳规律及调控深松秸秆全量还田的产量最高，常规耕作只比免耕高1.03%。转变耕作方式后，作物增产幅度每年达2.9%。保护性耕作转为深松耕作，有利于提高作物产量。秸秆全量还田比部分还田增产显著。保护性耕作农田的作物固碳量高于常规耕作，深松耕作固碳量最高；转变耕作方式和秸秆还田都有利于提高农田作物固碳量。3保护性耕作农田的土壤呼吸规律及影响因素保护性耕作农田玉米季土壤呼吸速率比小麦季平均高5.8倍。麦季农田白天土壤呼吸速率为夜间的1.1-1.5倍，玉米季是夜间的1.93倍。常规耕作方式的土壤呼吸最高，而免耕土壤呼吸最低。转变耕作方式后，除免耕外，土壤呼吸表现出降低趋势。秸秆还田量与土壤呼吸呈显著地正相关关系。土壤呼吸与20cm土壤有机碳极显著相关；在一定的土壤水分范围内，土壤呼吸与土壤水分正相关。保护性耕作农田年度土壤呼吸排碳量平均比常规耕作低1.3t/hm²,转变耕作方式后农田土壤呼吸与原方式相比增减范围在1.5%左右，秸秆还田增加土壤呼吸碳排量，常规全量还田是不还田的1.11倍。4保护性耕作下农田生产投入对碳循环的影响不同耕作方式的农田年度生产性碳投入相差较小，总量相差不到2.5%。在小麦生产中，除深松耕作外，常规耕作机械碳排放量最大。.玉米生产机械碳排量仅相当于小麦季的75.8%。麦-玉两季的生产资料的投入比较接近。化肥碳投入占总量的一半以上。不同处理的麦-玉两熟农田，玉米的生产利润平均是小麦的1.14倍。全年效益最高的耕作方式是深松耕作，达到20691.4元/hm²，除免耕外，保护性耕作的经济效益要高于常规耕作。保护性耕作农田生产投入的碳排放与常规耕作相比，除机械碳排量有差异，总体并不显著，但经济效益相差显著。5保护性耕作农田温室气体的排放规律及影响因素5.1CH₄的排放规律及影响因素保护性耕作农田表现为大气CH₄的汇，夏季高，冬季低；玉米生长季CH₄吸收平均水平比麦季高4～5倍。保护性耕作农田CH₄吸收小于常规耕作。秸秆还田减少了甲烷吸收通量。转变耕作方式增加了CH₄吸收量，但增量不到2%。保护性耕作农田CH₄吸收主要与耕作方式、秸秆还田量等相关。常规耕作CH₄吸收通量比相应的免耕处理要高8.65%。CH₄的吸收通量与地表温度显著性正相关。CH₄的吸收通量与土壤水分负相关,与土壤有机碳呈显著的正相关性。常规耕作农田年度CH₄吸收量比保护性耕作平均高10.5%，保护性耕作方式转变对CH₄吸收量略有提高，年均4.34%。全量秸秆还田比不还田年度减少CH₄吸收量约12.7%。5.2N₂O的排放规律及影响因素保护性耕作农田N₂O排放具有明显的季节变化。N₂O日排放呈现昼高夜低的变化趋势。N₂O排放量随温度的变化升高。玉米季节N₂O排放通量高于麦季。常规耕作农田年度N₂O排放比保护性耕作平均低2.3%，保护性耕作方式转变对N₂O排放略有提高，年均2.27%。全量秸秆还田比不还田农田年度N₂O排放量高约8.1%。5.3CO₂的排放规律及影响因素保护性耕作农田CO₂排放玉米季比小麦季高2.1倍。耕作方式转变后，CO₂排放量较原耕作方式降低。随着秸秆还田量的增加，CO₂的排放量增加；CO₂的排放与大气温度呈显著的正相关性。常规耕作农田CO₂年度排放平均比保护性耕作高2.43tCO₂·hm^-2·a^-1。转变耕作方式后CO₂排放平均比对照降低0.93tCO₂·hm^-2·a^-1，秸秆还田促进了农田的CO₂排放，全量还田比不还田高14.4%。保护性耕作农田全年的CO₂排放占总温室效应的97.4%，N₂O占2.88%，而CH₄的吸收只占0.27%。降低农田温室气体的温室效应，主要是降低农田CO₂的排放。适量的秸秆还田和耕作方式的转变都利于减少农田温室效应。6不同玉米秸秆还田方式的确定玉米秸秆的能量值底部最高，而主要营养成分顶部最高，从综合利用角度评价，留茬0.5m秸秆还田比较合理。7保护性耕作农田的碳循环规律和碳效率7.1保护性耕作农田生产的碳效率保护性耕作农田的深松耕作的碳效率最高，免耕处理的碳效率最低。转变耕作方式和秸秆还田显著提高农田的碳效率。玉米生产的碳效率高于小麦。7.2保护性耕作农田的碳循环规律保护性耕作农田生态系统中，深松耕作的年度净固碳量最大，达到5.801tCE/hm²，最少的是常规耕作，比深松相差2.199tCE/hm²。免耕转深松后，固碳量提高了22.96%。秸秆还田不能显著提高农田生态系统年度净固碳量，与还田量并不成线性关系。0.5米的玉米秸秆还田是较好的提高农田生态系统固碳量的途径。在整个农田生态系统的碳循环中，土壤呼吸排放碳量占年度总量的40.66%，生产投入占4.11%，农田CH₄吸收量占0.1%，作物固碳为55.13%，土壤固碳占4.97%。要减少农田碳排放，主要是减少土壤呼吸的量，增加作物固碳量。保护性耕作及转变耕作方式都能显著提高农田净固碳量。7.3保护性耕作农田的碳生态足迹深松耕作农田的碳生态盈余最高，常规耕作方式最低，仅占深松的55.8%。转变耕作方式显著地增加碳生态盈余：免耕变为深松后，碳生态盈余提高了16.6%。碳生态盈余与秸秆还田量并不呈比例关系，0.5米的秸秆还田方式碳生态盈余最大。综上所述，保护性耕作技术作为常规耕作的替代方式，无论是理论方面，还是生产实践技术方面都具有固碳减排的可行性。改变耕作方式和适量的秸秆还田都是较好的增加农田固碳、实现低碳生产的有效方法。更多还原

【Abstract】 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.更多还原