【作者】 慕平；

【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】 本试验以陇东黄土高原全量玉米秸秆连续3年（H3）、6年（H6）、9年（H9）还田的玉米种植农田为对象，研究在全量、多年秸秆还田措施下的土壤耕层碳汇特征、土壤理化性状变化、土壤生物活性响应及地上作物生长发育特性反应。在科学评价秸秆还田措施下农田综合地力变化的基础上，探讨各指标因子间相互作用关系及调控机理，为该区全面提升地力水平，增加碳汇水平提供有益参考。主要结果如下：1．连年全量玉米秸秆还田处理下，大量有机碳源的投入，有效改善了土壤物理性状，表现为土壤0-40cm土层中大于0.25mm水稳性团聚体比例显著增大，还田9年处理R0.25较对照增幅达到34.6%。同时，土壤容重及孔隙度等物理性状指标显著改良，使土壤固-液-气三相结构趋于合理。土壤结构的改善，明显促进了土壤保水、控温性能的发挥。0-200cm土层土壤含水量呈还田处理9年>6年>3年>不还田的趋势，其中9年、6年、3年还田处理，0-40cm土层深度中土壤饱和导水率较不还田对照分别高11.2%、17.6%和23.8%。2.土壤养分因子对连续全量秸秆还田表现积极响应。不同还田年限处理下土壤0-20cm耕层中全氮、全磷、碱解氮、速效磷及速效钾含量均有不同程度增加。还田9年处理的全氮、全磷、速效钾分别较对照增加47%、17%和23%，但随着土层深入，不同肥力因子增加幅度在处理间存在差异，其中速效钾、全氮增长较为显著，全磷、速效磷、碱解氮增幅较小,还田增肥效应显著降低.3.连续秸秆还田使0-30cm耕层细菌、真菌、放线菌群体数量明显增加，且随还田年限增加而增长。其中以细菌表现最为突出，较对照增加87.4%；其次是放线菌，增长63%，真菌增长26%。全量连年还田能有效增加土壤微生物多样性和菌系分布的均匀度，其中还田9年处理的Shannon-Winer指数和Pielous均匀度指数分别达到0.64和0.42，较对照增高19.3%和17.4%。另外从玉米生长季根际土壤酶活性的响应来看，其活性表达水平与玉米生长发育和土壤环境因子密切相关，呈现明显的根际效应和时空效应。连续多年全量玉米秸秆还田有效提高了根际土壤脲酶、碱性磷酸酶、蔗糖酶、过氧化氢酶活性水平，各处理间均表现出随还田年限增加而加强的特点，在吐丝期玉米由营养生长向生殖生长转变，是全生育期中生长最为旺盛的时期，其土壤酶活性水平亦达全年最高值。4.灌浆期是玉米生长发育和产量形成的关键时期，不同秸秆还田年限处理对该生育时期玉米光合性能产生明显影响。随着还田年限延长，玉米叶片净光合速率、蒸腾速率、气孔导度明显提高，同时叶面积指数和灌浆期叶片叶绿素含量也明显提高。还田9年较对照增加29.83%，其他处理间差异未达显著水平。5.产量和总生物量的增加是检验耕作措施好坏的重要指标，不同还田年限玉米籽粒产量差异显著，反映出秸秆还田措施能够促进玉米籽粒产量的提高，且与还田年限呈正相关。其中还田9年处理下玉米产量达到12624.5kg.hm^-2，分别较还田6年、3年、不还田处理增加12.3%、24.6%和35.4%；而其他性状如灰分、粗蛋白、粗脂肪等品质性状表现相对稳定，处理间差异不显著。但秸秆叶绿素含量、籽粒中蛋白质含量及可溶性糖含量等在处理间表现6%¹9%的差异。试验中0-40cm土层中玉米根重密度、总根长、根系活力值均表现为还田处理下大幅增加；吐丝期各项发育指标达最大值，至成熟期出现衰退，但还田处理能有效减缓成熟期根系衰退的趋势。对延长根系作用时间，争取后期产量的形成发挥重要作用。6.连年全量玉米秸秆还田处理，能显著提升土壤碳汇水平和潜力。0-20cm耕层中有机碳、碳密度均较对照显著增高，且处理间呈现还田9年>6年>3年>不还田的趋势，还田9年的有机碳和碳密度值分别较对照增加156%和188%。虽然耕层0-20cm中年有机碳的年累积量及增长率表现随还田年限增加而下降的趋势，但距离最大饱和量尚有较大的空间。不同秸秆还田年限处理下，玉米各生育期微生物量碳、微生物量氮和微生物量磷均较对照有较大幅度的增加，还田9年的平均微生物量碳值较对照高119.2%，反映土壤微生物积碳效应显著。7.借鉴前人有关土壤质量综合评价指标体系并结合本试验总体指标特点，筛选出涵盖土壤结构、养分供应、土壤微生物以及作物发育等与地力水平表现密切相关的12项指标对还田处理农田进行综合评价和各项评价指标的权重估算。获得评价模型：P_综=0.21X₁+0.11X₂+0.087X₃+0.064X₄+0.029X₅+0.18X₆+0.066X₇+0.063X₈+0.042X9+0.067X₁₀+0.061X₁₁+0.021X₁₂，其中R0.25、有机碳和产量在指标体系中权重较高，分别达0.21、0.11和0.18，对不同还田处理评价结果呈H9>H6>H3>H0，与现实表现一致。综上所述，连续多年全量玉米秸秆还田在陇东黄土高原较为贫瘠的农田中，可以促进土壤碳汇，显著增加表层土壤有机碳、碳密度，促进土壤微团聚体增加，改善土壤固-气-液三相比结构，有效增加土壤有机质、全氮、全磷等养分；改善土壤微生物区系结构，增加耕层土壤中微生物碳、氮、磷含量并使之达到较高水平的平衡状态，从而为作物生长发育特别是根系发育及根际土壤酶活性提高打下基础。并最终促进玉米在该产区连作条件下仍然获得较高而稳定的生物产量。有力提高了陇东黄土高原综合地力水平，促进该区农田生产力的全面提升。更多还原

【Abstract】 The experiment was conducted in maize breeding experimental site in Pingliang onLoess Plateau, under the condition of3,6and9years of continuous entire maize stalkreturinging into field, soil carbon sequestration, physical and chemical property, soilbioactivity, as well as maize growth and development characteristics were studied. Based onscientific evaluation of integrated soil fertility variation, the relationships among differentfactors were discussed to provide reference to soil fertility and carbon sequestrationimprovement. The main results are as follows:1. Under the condition of continuous all maize stalk returingin into field, plenty oforganic carbon input improved soil phical property. The proportion of>0.25mm Waterstable aggregate in0-40cm soil increased significantly. Treatment R0.25of H9increased34.6%compared with the control. Meanwhile, soil bulk density and porosity got improvedand solid-liquid-gas structure tended to reasonable. All these improvement promoted waterconservation and temperature modulation of soil. Moisture content at0-200cm showedH9>H6> H3>H0,11.2%,17.6%and23.8%increase in0-40cm soil saturate waterconductity were observed.2. Soil nutrients had active responses to continuous entire maize stalk returinging intofield. Total N, P alkaline hydrolytic N, available P and K at0-20cm soil increased.47%,17%and23%increment of TN, TP and available K were observed under H9treatment. Theeffectiveness of increasing fertility by stalk returining declined with the increasing soildepth.3. Continuous stalk returning resulted in remarkable increase of bacteria, fungi andactinomyce at0-30cm soil. Compared with the control, baceria increased87.4%,actinomyce increased63%and26%in fungi. Under the treatment of H9, Shannon-Winerindex and Pielous uniformity index reached0.64and0.42, increased19.3%and17.4%,respectively. Continuous stalk returning improved the activity of soil urease, Alkalinephosphatase, sucrose enzyme and Catalase effectively, showing H9>H6>H3>H0. Vegativegrowth changes into reproductive growth at silking stage, when the most prosperous growthoccurs, and also the highest activity level of soil enzyme.4. Milking stage is the crucial period for maize growth and grain formation, stalkreturning treatment had significant influence on maize photosynthesis at this stage. With the increasing time of treatment, net photosynthetic rate, transpiration rate and stomatalconductance improved, as well as Leaf area index and chlorophyll content. SOD, POD andCAT also increased. H9had393.52U·g-1FW of SOD, increased29.8%,32.73%and29.83%increment were also observed in POD and CAT, respectively. There is nosignificant difference among treatments.5. Significant difference was observed among different treatments in terms of maizegrain yield and total biomass, showing H9>H6>H3>H0. H9achieved17624.5kg.hm-2totalbiomass, increased12.3%,24.6%and35.4%compared with H6, H3and H0, respectively.Other factors such as crude ash, crude protein and fat were stable and there is no significantdifference. But6-19%difference was observed on ahlorophyll content, grain protein andsoluble sugar content. Root weight, density, total root legth and root activity at0-40cm soilwere increased under the treatment and reached the highest at silking satge. Then declined atmaturity, but the declination was delayed compared with the control.6. Stalk returning treatment significantly increased soil carbon sequestration andpotential. Organic carbon and carbon density at0-20cm soil showed H9>H6>H3>H0,compared with the control, SOC and DSOC of H9increased156%and188%, respectively.MBC, MBN and MBP of maize at each growth satge also increased under treatment.Average MBC of H9increased119.2%, indicating a significant effect of carbonaccumulation of soil microorganism.7. According to published comprehensive evaluation system of soil quality combined withthe experiment,12factors closely related to soil integrated fertility were selected forcomprehensive evaluation and weight estimates, including soil structure, nutrient supply,soil microorganism and maize growth and development. The evaluation model is: P=0.21X₁+0.11X₂+0.087X₃+0.064X4+0.029X₅+0.18X₆+0.066X₇+0.063X₈+0.042X₉+0.067X₁₀+0.061X₁₁+0.021X₁₂，where R0.25,organic carbon and grain yield had weight of0.21,0.11and0.18. The evaluation result showed H₉>H₆>H₃>H₀, coincidence with the reality.To sum up, for sterile farmland in Longdong Loess plateau, continuous maize stalkreturning into field could increase soil organic carbon, carbon density and soil aggregates,improve soil solid-liqued-gas structure, soil organic matter, TN, TP and microorganismfauna structure, as well as C, N P content of microorganism and keep a high and stable level.This would establish a soild base for plant growth and development, keep high and stableyield under succession cropping, and help to increase soil integrated fertility and productivity in Loess Plateau.更多还原