【作者】 刘朝巍；

【导师】 张恩和；

【作者基本信息】 甘肃农业大学 ， 作物栽培学与耕作学， 2012， 博士

【摘要】 农田中土壤碳排放量过高和硝态氮损失均会导致土壤肥力下降,影响作物产量并对环境产生污染。适宜的留茬方式和种植模式可以增加土壤碳固存,减少农田碳排放、增加作物氮素利用,降低土壤硝态氮损失的风险,保证作物产量。2010-2011年,在甘肃省河西绿洲灌区甘肃农业大学武威试验站,在单作小麦、单作玉米、小麦/玉米间作三种种植模式下,设置翻耕秸秆还田(TIS)、免耕立茬(NTSS)、翻耕秸秆焚烧(T,仅2010年)、免耕焚烧(NT,仅2011年)等不同留茬方式,研究留茬方式对不同种植模式下农田土壤呼吸和碳平衡、农田氮平衡、土壤物理性状、作物产量和生长发育等指标的影响。主要研究结果如下：1.在河西绿洲灌区,作物籽粒含氮量三种种植模式对留茬效应影响不同,基本规律为免耕立茬处理比其他留茬方式更有利于提高作物籽粒含氮量,免耕焚烧处理其次；植株总吸氮量受作物种类,作物前茬和留茬方式多方面影响。在小麦单作农田,翻耕秸秆是否还田对植株总吸氮量影响不显著(TIS和T),翻耕还田和免耕立茬比免耕焚烧显著提高植株吸氮量；在小麦间作带,不同留茬方式间均差异不显著；在玉米单作农田,前茬为小麦茬时,免耕立茬和翻耕秸秆还田与翻耕焚烧相比均能提高小麦植株总吸氮量,前茬为玉米茬时,免耕处理(NTSS和NT)均比翻耕秸秆还田处理植株吸氮量显著提高；在玉米间作带,前茬为小麦茬时,免耕立茬和翻耕秸秆还田均可以提高植株吸氮量,而前茬为玉米茬时,免耕处理(NTSS和NT)比翻耕秸秆还田更能提高植株吸氮量；种植模式间比较(2010-2011留茬方式均值),单作小麦植株总吸氮量显著低于单作玉米和小麦／玉米间作,单作玉米和小麦／玉米间作处理间差异不显著,单作小麦植株总吸氮量比单作玉米和小麦／玉米间作分别低11.47%和10.47%。2.免耕立茬和翻耕秸秆还田可以增加表层土壤硝态氮分布(0-20cm),前茬为小麦茬比玉米茬对土壤硝态氮分布影响更显著。综合两年试验可得,在单作小麦农田,免耕立茬和翻耕秸秆还田可以缓解硝态氮向下运移,降低损失风险；在小麦间作带,翻耕秸秆还田比不还田可以显著增加表层(0-20cm)土壤硝态氮含量,降低土壤硝态氮含量下移,免耕留茬比不留茬显著降低土壤硝态氮下移；在单作玉米农田,前茬为小麦茬时,不同留茬方式对0-60cm土层土壤硝态氮含量影响显著,前茬为玉米时仅影响0-20cm土层硝态氮含量。在玉米间作带,土壤硝态氮分布规律与单作玉米相似。3.免耕立茬处理可以显著降低土壤硝态氮损失,翻耕焚烧处理损失风险最高。在单作小麦种植中,翻耕秸秆是否还田对土壤硝态氮的损失无显著影响,免耕留茬比不留茬显著降低土壤硝态氮损失量；在单作玉米种植中,无论前茬为小麦还是玉米,免耕处理(NTSS和NT)均能显著降低土壤硝态氮损失量；在小麦/玉米间作种植中,前茬均为小麦茬口时(2010),免耕立茬和翻耕还田处理可以降低硝态氮的损失,前茬为小麦/玉米混合茬口时(2011),免耕处理可以有效降低硝态氮损失。在2010年,NTSS、T和TIS土壤硝态氮损失量分别为35.61、49.49和39.67kghm-2, NTSS和TIS分别比T处理低28.04%和10.23%,在2011年,TIS、NT和NTSS的硝态氮损失量分别为38.7、27.77和21.07kghm-2, NTSS和NT的硝态氮损失量比TIS分别低17.63和10.93kg hm-2。4.不同处理土壤呼吸速率生育期均呈单峰曲线变化,峰值出现在作物生长最旺盛的时期,但具体峰值出现时间有所不同。不同留茬方式间比较,免耕比翻耕处理土壤呼吸速率显著降低,不同种植模式间排序为单作小麦>小麦/玉米>单作玉米。免耕对土壤呼吸速率的影响作用大于秸秆还田的作用；不同处理土壤呼吸的日变化均呈单峰曲线变化,日变化幅度为小麦/玉米间作<单作小麦<单作玉米,免耕立茬对单作小麦峰值出现时间(14：00)比翻耕处理(12：00)有所延迟,对单作玉米和小麦/玉米间作影响不显著。同一种植模式下不同留茬方式间比较均为NTSS处理净生态系统生产力(NEP)最高,在单作小麦农田,2010年,NTSS处理的NEP比TIS和T处理高1671和1276kgChm-2,2011年,NTSS处理比TIS和NT处理高1822和4124kg C hm-2;在单作玉米农田,前茬为小麦茬时,NTSS处理比TIS和T处理高2248和4231kg kg Chm-2(2010),前茬为玉米茬时,NTSS处理比TIS和NT处理高1969和1219kg C hm-2;在小麦/玉米间作中,NTSS处理比TIS和T处理高2150和3293kg C hm-2(2010), NTSS处理比TIS和NT处理高974和1663kgChm-2(2011)。将同一种植模式下不同留茬方式求平均值,单作小麦、单作玉米、小麦／玉米间作NEP分别为3166、4060和4161kgChm-2,单作玉米和小麦／玉米间作的NEP比单作小麦分别高894和995kg C hm-2,说明三种种植模式中小麦／玉米间作碳汇的作用最高,单作小麦最低。5.在不同种植模式下,免耕留茬比免耕焚烧产量显著提高,其他留茬处理间大都差异不显著。在小麦单作农田,免耕立茬和翻耕还田可以显著提高单作小麦籽粒产量,分别比免耕焚烧处理高12.13%和8.80%；不同留茬方式对小麦间作和玉米单作籽粒产量无显著影响；在玉米间作带,在2010年,NTSS的籽粒产量显著高于T处理,NTSS与TIS、TIS与T处理间差异不显著,NTSS的籽粒产量比TIS和T分别增加3.34%和7.24%。在2011年,NTSS、TIS和NT间籽粒产量差异不显著；在小麦/玉米间作中不同留茬方式间籽粒产量差异不显著。6.在小麦单作农田,NTSS水分利用效率(WUE)显著高于TIS、T处理和NT处理,TIS与(翻耕或免耕)焚烧处理之间差异不显著,在2010年,NTSS的WUE比TIS和T分别增加16.13%和20.37%,在2011年,比TIS和NT分别增加9.01%和17.41%。在小麦间作种植中,规律与单作相似,在2010年,NTSS的WUE比TIS和T分别增加14.53%和14.87%。在2011年,分别比TIS和NT高8.66%和12.51%；玉米农田在2010年,NTSS处理显著高于TIS和T处理,TIS和T处理间差异不显著,在单作种植中,NTSS的WUE比TIS和T分别增加10.90%和16.73%。在间作种植中,分别增加11.85%和17.07%。在2011年,前茬为玉米茬时不同留茬方式间均差异不显著；在小麦/玉米间作中,NTSS处理WUE显著高于TIS、T和NT处理。TIS与(翻耕或免耕)焚烧处理之间差异不显著,NTSS的籽粒产量比T和TIS分别增加12.87%和17.55%(2010)。比TIS和NT分别增加7.54%和9.61%(2011)。7.不同留茬和种植模式下,土壤呼吸受土壤温度和作物生长的影响明显,而受水分的影响规律不明显。0-5cm土壤温度与土壤呼吸速率相关性最高。在小麦和玉米单作农田,土壤呼吸和温度的回归系数均为免耕立茬处理最低,在小麦／玉米间作中,前茬为小麦时与单作规律相似,前茬为小麦／玉米混合茬口时,土壤呼吸和温度之间无显著相关；不同留茬和种植模式土壤呼吸与0-10cm土壤含水量无显著相关关系；土壤呼吸速率与干物质累积速率呈显著正相关关系,不同种植模式间R2排序为单作玉米>单作小麦>小麦／玉米间作8.综上所述,从减少土壤碳排放、降低土壤硝态氮损失、增加作物产量和WUE等方面考虑,河西绿洲灌区最适宜的留茬和种植模式为小麦／玉米间作体系下免耕立茬种植,土壤硝态氮损失主要受硝态氮在土壤中的分布和植物吸氮量两方面影响,土壤呼吸主要受土壤温度和作物生长两方面的影响,与土壤水分相关不显著,间作体系下影响有所降低。更多还原

【Abstract】 High soil CO2emissions and nitrate leaching can lead to decline in soil fertility, whichcause crop yield decline and environmental pollution. Suitable cropping system and standingmode can enhance soil C sequestration, reduce soil CO2emissions, improve nitrogen (N)uptake efficiency, reduce nitrate leaching, which result in crop yield increase. A fieldexperiment was conducted to investigate the effect of tillage and crop treatments on soil CO2emissions, carbon and nitrogen balance, soil physical properties, and crop yield and growthdevelopment in Gansu Agricultural University Experimental Station in Wuwei city in the theHexi Oasis irrigation, Gansu province during2010to2011. The experiment consisted of threetypes of standing mode: sole wheat, sole corn and wheat/corn intercropping, and four types oftillage pattern: tillage with stubble incorporated, no tillage with stubble standing and tillagewith stubble burning only conducted in2010, no tillage with stubble burning only conductedin2011. The main results are as follows:1. N content in crop seeds was affected by cropping pattern in three standing mode, thebasic law of which was crop seed N content under NTSS was at the first place, crop seed Ncontent under no tillage with stubble burning was at the second place; plant total N uptakediffered among crop species, previous crops and tillage method. In sole wheat, plant total Nuptake did not differ significantly from T and TIS, but higher under TIS and NTSS than underNT; In intercropped wheat, plant total N was not affected by tillage methods; In sole andintercropped corn, when previous crop is wheat, plant total N was higher under NTSS and TISthan under T; when previous crops is corn, plant total N was higher under NTSS and NT thanunder T; results from Comparison of standing modes, plant total N under sole wheat waslower than under sole corn and wheat/corn intercropping for11.47and10.47%, respectively.There were no significant differences existed between sole corn and wheat/corn intercropping.2. Soil nitrate distribution was higher under NTSS and TIS than under other tillagemethod at020cm. when previous crops were wheat, it is significantly higher than corn. Formtwo years experiment results, we found surface soil soil nitrate content of sole wheat underNTSS and TIS was higher than under other tillage method, which can decrease the leaching loss of nitrate from soil; the risk of soil nitrate losses through leaching after stubble return waslower when compared with stubble burning in tillage and no tillage treatment; soil nitrate wasnot changed significantly by tillage at060cm depth layers for sole corn when previous cropsis wheat, but significantly different was found at020cm depth layers when previous crops iscorn. The same trend was found in intercropped corn.3. NTSS can reduce the soil nitrate leaching; T treatment had the highest risk of soilnitrate leaching. The risk of soil nitrate losses through leaching after stubble return was lowerwhen compared with stubble burning for sole wheat in tillage treatment, there was nodifference existed between TIS and T; sole con under NTSS and NT had lower soil nitrateleaching than other tillage method; NTSS and TIS for intercropping system could reduce thesoil nitrate leaching when previous crop is wheat (2010), and this effect is found in no tillagesystem when previous crop is corn (2011). The soil nitrate leaching, in NTSS┚T and TIS,were35.61,49.49and39.67kg hm2in2010, and were38.7┚27.77and21.07kg hm2in2011.Compared with the T treatment, the decreases of soil leaching in the NTSS and TIS were28.04%and10.23%respectively in2010, Compared with the TIS treatment, the decreases ofsoil leaching in the NTSS and NT, were17.63and10.93kg hm2respectively in2011.4. The different treatment of soil respiration rate growth period showed a single peakcurve, the peak appears in the most productive period of crop growth, but the specific peaktimes vary. Soil respiration was significantly lower under no tillage than tillage, the order ofdifferent standing mode was sole wheat> wheat/corn> sole corn. No tillage had moresignificant impacts on soil respiration than residue; different treatment of the diurnal variationof soil respiration showed a single peak curve, diurnal variation of wheat/maize intercropping<monoculture wheat <monoculture corn, the highest soil respiration in daytime under NTSS(14:00) was later than tillage treatment (12:00) for sole wheat, but this was not found in solecorn and wheat/corn.NEP was highest under NTSS in the same standing mode, NTSS for sole wheatincreased NEP compared to TIS and T by1671and1276kg C hm2(2010), and compared toTIS and T by1822and4124kg C hm2, respectively. NTSS for sole corn increased NEPcompared to TIS and T by2248and4231kg C hm2while previous crop is wheat (2010), and compared to TIS and T by1969and1219kg C hm2while previous crop is corn (2011),respectively. NTSS for wheat/corn increased NEP compared to TIS and T by2150and3293kg C hm2(2010), and compared to TIS and T by974and1663kg C hm2(2011), respectively.The NEP, in sole wheat┚sole corn and wheat/corn intercropping, were3186┚4060and4161kg C hm2. Compared with the sole wheat treatment, the increase of NEP in the sole cornand wheat/corn intercropping, were874and975kg C hm2, respectively, carbon sequencewas highest under wheat/corn, and was lowest under sole wheat.5. The grain yield was higher under NTSS than NT; there were no differences underother tillage. NTSS and TIS for sole wheat increased grain yield compared to NT by12.13%and8.80%, respectively. But there were no differences under intercropped wheat, sole corn;NTSS for intercropped corn increased grain yield compared to TIS and T by3.34%and7.24%, respectively. But there were no differences under three tillage methods in2011. Grainyield for wheat/corn intercropping was not impacted by tillage method.6. The NTSS treatments for sole wheat had16.13and20.37C hm2higher WUE thanTIS and T (2010), and9.01%and17.41%higher WUE than TIS and NT (2011). The similartrend were found in intercropped wheat, The NTSS treatments for sole wheat had14.53%and14.87%C hm2higher WUE than TIS and T (2010), and8.66%and12.51%higherWUE than TIS and NT (2011); The NTSS treatments for sole corn had14.53%and14.87%C hm2higher WUE than TIS and T, and for intercropped had8.66%and12.51%higherWUE than TIS and T. There was no difference under tillage while previous crop is corn; TheNTSS treatments for wheat/corn intercropping had12.87%and17.55%C hm2higher WUEthan TIS and T (2010), and7.54%and9.61%higher WUE than TIS and NT (2011).7. Under different tillage method and standing mode, soil respiration was significantlyaffected by soil temperature and crop growth, while soil water content was not a significantaffect factor. Soil temperature was highly correlated with soil respiration rate in05cm soillayer. sole wheat and corn under NTSS showed the lowest regression coefficients betweensoil respiration and temperature, There were no differences existed under different tillage inwheat/corn intercropping when previous crops is wheat/corn. Soil respiration wassignificantly correlated to soil water content in010cm soil depth; soil respiration rate and dry matter accumulation rate showed a significant positive correlation. Under the differentstanding mode, the order of R2was sole wheat> wheat/corn intercropping> sole corn.In summary, from the view of reducing soil carbon emission, reducing nitrate leachingand increasing crop yield and WUE, the most appropriate tillage method and standing modewas wheat/maize intercropping under no tillage with stubble standing in the Hexi OasisIrrigation, nitrate leaching is mainly affected by nitrate distribution and plant nitrate N uptakefrom soil. Soil respiration is mainly affected by both soil temperature and crop growth,wheras soil moisture was not significantly correlated with soil respiration, the impact wasdecreased under intercropping system.更多还原