基于旱作麦田蓄水保墒技术的土壤结构与水分运移规律研究

Soil moisture is the most crucial limiting factor for winter wheat production in dryland. It is significant to improve the yield of dryland winter wheat by increasing the efficiency of precipitation utilization and the soil moisture storage ability during summer fallow period. The “Three in Advance Technology (TAT)”, which refers to soil deep tillage, residue management and organic fertilizer application in advance during the summer-fallow season, is widely adopted as an effective technology to conserve soil moisture on winter wheat production in dry farmlands in the south of Shanxi province. Most studies have concentrated on laws of spatial and temporal distribution and consumption of soil moisture recently. However, the law of soil moisture movement and its influencing mechanism hasn’t been figured out clearly, which will restrict the further improvement in precipitation use efficiency. Therefore, based on our former research, this project is to analyze the effects of different technologies of water conservation on soil hydrodynamic parameters. The technology of X-ray computed tomography and digital image processing are adopted to analyze the changes of soil structure quantitatively. The objective focused on clarifying the responding mechanism of soil hydrodynamic parameters to the changes on soil structure, determining the effect of both them on the growth and yield formation of winter wheat. Furthermore, using the coupling model of HYDRUS-EPIC assess the change of soil moisture and the dynamic of growth and development of winter wheat under different technologies in dryland. Overall, those results will provide the theoretical support for improving precipitation use efficiency and raising production of winter wheat in dry farmlands.

土壤水分是旱作冬小麦生产最为关键的限制因子，提高降水利用效率、增加休闲期土壤蓄水量是实现旱地小麦稳产增产的重要途径。以“提前深翻或深松、提前深施有机肥、提前秸秆还田或覆盖”为主体的“三提前”技术，因其良好的蓄水保墒作用而被广泛应用于晋南旱地冬小麦的生产中。但是，该技术下关于土壤水分的研究主要集中在其时空分布与积耗方面，而土壤水分运移规律及影响机制尚不清楚，限制了旱地小麦降水利用效率的进一步提高。因此，本项目拟在前期研究的基础上，进一步研究不同蓄水保墒技术对土壤水动力学参数的影响，并采用同步辐射显微CT与数字图像处理技术定量解析土壤结构特征的变化；阐明土壤水动力学参数对土壤结构变化的响应机制，明确二者变化对小麦生长和产量形成的影响；在以上研究基础上，利用HYDRUS-EPIC耦合模型评价不同蓄水保墒技术下土壤水分变化与小麦生长动态，为进一步提升旱地小麦降水利用效率和生产力提供重要的理论支撑。

土壤水分是旱作冬小麦生产关键限制因子，提高降水利用效率、增加休闲期土壤蓄水量是实现旱地小麦稳产增产的重要途径。以夏闲期耕作为核心的旱地麦田蓄水保墒技术，是黄土高原地区旱作农业的一大技术特色。然而该技术下土壤水分蓄积的动力学机制尚不清楚，限制了旱地小麦降水利用效率的进一步提高。本项目研究了夏闲期免耕（FNT）、夏闲期深翻（FPT）和夏闲期深松（FST）三个处理下的土壤水分时空分布，分析了土壤结构特征和土壤水动力学参数的变化，利用模型评价不同夏闲期耕作下土壤水分运移规律与作物生长状况。主要研究结果如下:.（1）随耕作年限的推移，FNT处理较FPT处理改善了0-50cm土壤机械稳定性团聚体分布，降低了水稳性团聚体的破坏性，逐渐增强了团聚体稳定性。FNT增加了0-20cm的土壤容重，而FST处理增加了30-50cm土壤容重。.（2）FST处理0-20cm土壤总孔隙度和充气孔隙度较高，提高了孔隙平均路径长度和欧几里得距离；而FPT处理下30-50cm土壤总孔隙度和充气孔隙度较高。.（3）FPT处理较FNT处理0-30cm土壤水分稳定入渗速率、平均入渗速率、累计入渗量分别显著降低了69.57%、53.93%和62.65%，平均瞬时入渗速率降低了58.87%。FPT较FNT处理土壤饱和导水率降低了25.76%-62.27%。.（4）0-10cm土壤水分吸附等温线以FST处理最高，10-30cm以FPT处理最高，说明FST和FPT处理分别在0-10cm和10-30cm土壤蓄积更多水分。.（5）FPT和FST处理较FNT处理显著增加0-200cm剖面播前底墒，其水分效应可延续至拔节期或开花期，能够提高小麦干物质量，增加群体分蘖，提高水分利用效率10.13%-13.18%，实现小麦增产14.46%-26.38%。.（6）Oswin-KRH50模型模拟土壤水分吸附等温线效果更佳。APSIM-Wheat模型能够较为精确地模拟夏闲期耕作处理下旱地冬小麦生长发育情况和麦田土壤水分，模拟得出FPT处理能够提高土壤蓄水保墒潜力并实现增产。.综上，FPT和FST处理改善了耕层土壤孔隙结构，提高了播前底墒和水分利用率，增加了产量，而FNT处理改善了土壤团聚体稳定性，增加了土壤水分入渗和导水，夏闲期耕作下土壤蓄水的水动力学机制仍需进一步深入研究。