【作者】 赵永敢；

【导师】 逄焕成；

【作者基本信息】 中国农业科学院 ， 作物生态学， 2014， 博士

【摘要】 针对内蒙古河套灌区地下水位浅，蒸降比大，土壤盐分运移以“上行”占优势，盐分表聚严重，作物产量低等突出问题，本研究提出了以隔断盐渍土壤水盐运移通路，创建淡化肥沃耕层为理论核心的盐渍土改良新技术——地膜覆盖结合秸秆隔层（简称上膜下秸）技术。2011~2013年以玉米秸秆为隔层材料，通过室内土柱模拟试验，对比研究了秸秆隔层及不同秸秆组分、长度与埋深对土壤水分入渗、蒸发、毛管水运动及土壤水盐运移的影响；同时结合3年微区定位试验，研究了“上膜下秸”以及不同秸秆用量与埋深对周年农田土壤水盐运移的影响；并通过2年大田验证试验，研究了“上膜下秸”对向日葵生长发育及产量的影响。旨在全面、系统的揭示“上膜下秸”技术对土壤水盐运移和作物生长发育及产量的调控机理。主要研究结果如下：1.土柱模拟试验结果表明，“上膜下秸”对土壤水盐运移的调控作用主要表现为：提高隔层上部土壤含水率，促进盐分淋洗，抑制土壤蒸发，阻隔盐分上行，减轻盐分表聚等。（1）在土壤水分入渗过程中，秸秆隔层降低了单位历时的累积入渗量和湿润锋移动速度，具有阻水减渗作用，从而可提高隔层上部土壤含水率，促进盐分淋洗。同时，还引发了湿润锋的不稳定性，即优先流现象的出现。秸秆隔层对水分入渗的阻碍作用具有阶段性，会随隔层与土层导水率差异的减小而减弱，入渗过程也会由非线性过程转变为线性过程，但其对隔层上部土壤水分的储蓄作用是较长期的。秸秆隔层的阻水性能主要与其内部结构有关，主要是孔隙度引起导水能力的差异。随秸秆隔层内部孔隙度增大，其阻水作用减弱。（2）在水分蒸发过程中，秸秆隔层具有抑制隔层下部土壤水分蒸发、控制盐分上行的作用。强烈蒸发作用下，土表形成的干燥层提高了土壤温度，加速了秸秆隔层内部汽态水运动，增大了气体比例，形成阻碍水盐上移的“阻隔层”，进而增大了其对隔层下部土壤水分蒸发的抑制作用，可将盐分控制在底层土壤中，有效地抑制了土表返盐。秸秆隔层对土壤水盐向上运移的阻碍作用与其内部孔隙度与埋深关系密切，随秸秆隔层内部孔隙度增大，其抑制作用呈先弱后强的趋势；随秸秆隔层埋深增加，其抑制作用呈减弱态势。（3）在毛管水运动过程中，秸秆隔层可抑制毛管水上升高度，且可降低毛管水在隔层下部土壤中的上移速度。当秸秆用量为5cm，距离地下水25cm时，毛管水无法越过隔层而上升，仅表现为隔层下缘不同程度浸润。随秸秆隔层内部孔隙度增大，其对毛管水上升高度的抑制作用增强，但对隔层下部土壤中毛管水上升速度的抑制作用减弱。（4）在浅层地下水埋深条件下，秸秆隔层可显著抑制潜水蒸发，结合地膜覆盖时尤为明显。连续蒸发30d内，秸秆隔层处理的累积蒸发量比对照降低了96.82%，其抑制作用明显优于地膜覆盖处理；而“上膜下秸”处理对潜水蒸发强度的抑制作用最大，其累积蒸发量比地膜覆盖处理降低了94.02%，同时还大幅度减弱了隔层上部土壤水分散失和盐分表聚，起到“保墒控盐”的双重作用。当地下水埋深为1m，秸秆隔层埋深小于或等于60cm时均可抑制潜水蒸发。不同秸秆隔层埋深处理对潜水蒸发的抑制作用差异较小，但处理间的储水抑盐效果差异明显。随秸秆隔层埋深增加，其储水作用增强，而对盐分表聚的抑制作用减弱。2.微区定位试验结果表明，在农田土壤环境下，“上膜下秸”可形成“上抑下隔”的水盐调控机制，为向日葵根系生长创造了“高水低盐”的微生态环境。（1）在向日葵播种前，秸秆隔层处理0~20cm和20~40cm土层平均含水率比对照处理分别提高了4.01%和3.10%，而平均含盐量分别降低了21.23%和29.60%。在向日葵生育期内，只埋设秸秆隔层处理对根层土壤的储水抑盐效果仅能维持至播种后30d左右，而“上膜下秸”处理能延续至播种后60d左右，在丰水年甚至更长。同时，“上膜下秸”处理能使根层土壤在整个生育阶段保持较低的盐分水平，显著降低了土壤溶液盐浓度，淡化根层作用明显，为向日葵根系生长提供了良好的土壤环境，从而促进了向日葵植株生长发育。（2）在地膜覆盖条件下，随秸秆用量增加，其对根层土壤的储水抑盐效果增强，且作用年限也随之延长。随秸秆隔层埋深增加，其对根层土壤的保水效果增强，而埋深为40cm时的控抑盐效果最为显著。综合保水、抑盐效果，建议农业生产中秸秆用量为12t/hm2，埋深为40cm。3.大田试验结果表明，“上膜下秸”明显可提升向日葵出苗和保苗能力，促进向日葵生长发育和增加产量。与传统耕翻处理相比，“上膜下秸”处理使向日葵苗期干物质日积累速率提高了35.30%；生育期提前了4~12d；净光合速率提高了4.87%~11.90%；成熟期株高、茎粗、叶面积和地上部干物质量分别提高了36.62%、16.44%、49.05%和42.60%；向日葵增产24.57%，达显著水平。更多还原

【Abstract】 Soil salinization is the major causes of declining agriculture productivity in the Hetao IrrigationDistrict of Inner Mongolia, China. In the circumstances of local shallow groundwater table, highevaporation, low precipitation and coupled with main upward movement of soil salt and severe saltaccumulation in the surface soil in this area, how to control the salt accumulation is very practical andurgent. This paper has proposed a new technique to restrain soil evaporation, retain moisture and controlsalinization thus helping to improve the saline soils and increase sunflower (Helianthus annuus L.) yieldthrough burying a straw layer in the soil and combing with plastic film mulch. In order to reveal effectsof plastic film mulch and buried straw layer on soil water, salt transport and sunflower growth, threetrails were conducted from2011to2013with maize straw as the experimental material. With the help ofsoil columns, the impacts of different straw parts, lengths and burial depths on soil water infiltration,evaporation, upward movement of capillary water and phreatic water evaporation were comparativelystudied in laboratory, as well as the distribution and transportation of soil water and salt during theprocesses. Meanwhile, a three-year micro-plot experiment was conducted to evaluate the effects ofstraw layer and its thickness and burial depth on soil water and salt transportation under planting.Moreover, a two-year field experiment was conducted to investigate the effects of plastic film mulchand straw layer burial on sunflower growth and yield. The main results are as follows:1. Results from the soil column simulation experiment showed that the combined application ofplastic film mulch and straw layer burial treatment altered the distribution and transportation of soilwater and salt in soil profile, including retaining more moisture in the topsoil layer, enhancing saltleaching, reducing the soil water and phreatic water evaporation, preventing the upward movement ofsoil water and salt, reducing sal accumulation.(1) In infiltration process, straw layer treatments effectively retarded water-flow and had anobvious effect of retaining water and leaching salts which in the topsoil. In infiltration process, the strawlayer treatments not only reduced the water infiltration rate and advanced wetting velocity, but alsoinduced the instability of wetting front, i.e., appearance of preferential flow. However, the benefit effectdeclined significantly with the decrease difference in hydraulic conductivity between straw layer andsoil layer. Then, the relationship between cumulative infiltration and time was converted fromnon-linear process into linear infiltration process. Meanwhile, straw layer treatments displayedsignificant long-term effect of storing soil water in the upper soil layer thereby helping to leach soil salt.Primarily, its effectiveness relates to the structure of straw layers, and it has more to do with strawinternal porosity which will make a difference in water conductivity. The more the internal porosity instraw layers the less inhibiting effect on water infiltration.(2) In evaporation process, straw layer treatment had an obvious effect of reducing soil evaporationand preventing the upward movement of soil water and salt. During the early days of evaporation, thesurface soil layer easy to be dried under intensive evaporation. Then, it can improve the soil temperature thereby to speed up the vaporized water movement and increase the proportion of gas in the straw layers.Consequently, it increased the effect on preventing soil water evaporation, and retained more water inthe subsoil layers. In addition, the salt upward movement in the straw layer treatments was controlled,and thus more salts been blocked in deep soil layers. Neverthless, the effect of straw layer on preventingthe upward movement of soil water and salt related to its internal porosity and burial depth. On the onehand, with the increase of internal porosity in straw layers, the inhibitory effect on preventing soil waterevaporation decreased in the early days while increased in the later. On the other hand, with the increasein straw layers burial depth, the inhibitory effect on preventing soil water evaporation decreased.(3) Compared to non-straw layer control, the height of capillary water was decreased in the strawlayer treatments. Also the rate of capillary water upward movement in the soil layers below straws waslowed. Capillary water did not cross the straw layers if it with5cm thick, but their bottom side weresoaked wet. With the increase of internal porosity in straw layers, the inhibitory effect on capillary waterupward movement increased; in contrast, the rate of capillary water upward movement increased in thesoil layers below straws.(4) Aside from the aforementioned, straw layer treatments dramatically reduced the evaporationfrom phreatic water under shallow groundwater table. During the30days of experiment, the cumulativeevaporation from phreatic water in the straw layer treatment decreased by96.82%, compared to uniformsoil. Plastic film mulch also reduced the evaporation relative to non-mulch. However, the straw layertreatment had94.02%lower evaporation than plastic film mulch. Moreover, the combined applicationof straw layer and plastic film mulch treatment performed better to against water evaporation than eithernon-mulch, or the individual use of straw interlayer or plastic film mulch. Therefore, the straw layerburial and plastic film mulch treatment had more moisture and less salt in the infiltration process, andreduced the soil water and phreatic water evaporation in the evaporation process, compared to othertreatments. In our experiment, straw layer had obvious effect on preventing groundwater evaporation ifits burial depth was equal to or less than60cm under plastic film mulch when the groundwater tablewas below1m. No significant differences in evaporation inhibitory effect were observed among thedifferent burial depth treatments. Nervertheless, with the increase of straw layers burial depth, the waterstorage capacity enhanced while the salinization control effect decreased.2. Results from the micro-plot experiment showed that the combined application of plastic filmmulch and buried straw layer treatment not only significantly enhanced water storage capacity of the0~40cm soil layer, but also continuously controlled salt accumulation.(1) In our experiment, the soil water content of0-20and20-40cm soil layer was4.01%and3.10%higher while the soil salt content was21.23%and29.60%lower in the straw layer treatments than innon-straw layer treatments before sowing, respectively. During the sunflower growing seasons, thestraw layer treatments had a higher soil water content of0-40cm soil layer than that of control on30days after sowing. However, the water retention effect sustained to approximately60days after sowingin the combined application of plastic film mulcha and straw layer burial treatment, particularly in wetyear. On the other hand, the plastic film mulch and straw layer burial treatment had a consistently and significantly lower soil salt content and soluble salt concentration of0-40cm soil layer than that ofother treatments throughout the growing season. Thus, it provided a better edatope for plants andimproved the development of sunflower.(2) In the fields, the desalinization effect increased significantly and service year also extendedremarkable with the thickness of straw layer when combined with plastic film mulch. It also observedthat the deeper the straw layer burial, the more water retention. However, the preferable burial depth forstraw layer to control salinization was40cm, which was in conformity with the actual agriculturalproduction.3. Results from the field experiment showed that the straw layer burial and plastic film mulchtreatment significantly improved emergence rate and sand establishment, promoted the growth ofsunflower and increased seed yield. Compared to neither straw layer nor mulch control, the straw layerburial and plastic film mulch treatment increased dry matter accumulation rate by35.30%at seedlingstage, shorted growth phases by4-12d and increased net photosynthetic rate by4.87%-11.90%,respectively. Moreover, the straw layer burial and plastic film mulch treatment increased plant height,stem diameter, leaf area and dry matter by36.62%,16.44%,49.05%and42.60%at maturity stage,respectively; it significantly increased seed yield by24.57%.更多还原