河西绿洲灌区保护性耕作的防风蚀效应

Hexi corridor is one of important commodity grain base, and is also one of the three largest sand dust source areas in China. In recent years, environmental problems result from sandstorm are attracting more attention. Soil wind erosion is the first link in sand-dust weather occurrence, farmland soil erosion is not only lead to the decline of land productivity, but also cause environmental degradation. Farmland soil erosion sediment is the important substance source, how to reduce farmland soil erosion is particularly important. Popularization and application of conservation tillage provide a good way to solve this problem. In irrigation oasis of Hexi Corridor of inland river basin, how much role are conservation tillage to control soil erosion played in? There have few studies about this, its mechanism is not very clear. Therefore, in this study, compared with conventional tillage as control, we will analyze soil characteristics and wind erosion characteristics under conservation tillage, and changing characteristics of soil characteristics and farmland wind erosion characteristics under different years of implementation of conservation tillage in this area, and then, analyze the relationship between crop stubble characteristics and farmland wind erosion characteristics, and the quantitative relationship between soil characteristics and farmland wind erosion characteristics, study the effect of conservation tillage on wind erosion control and its mechanism of action, and to provide evidence for evaluation of conservation tillage′s function to wind erosion control and taking reasonable and effective measures in order to control farmland wind erosion.

河西地区是我国重要的商品粮基地之一，也是我国三大沙尘源区之一。近年来，沙尘暴引起的环境问题被广泛关注。土壤风蚀是沙尘天气发生的首要环节，农田土壤风蚀不仅造成土地生产力下降，而且使环境恶化。农田土壤风蚀物是沙尘暴的重要物质来源，如何减少农田土壤风蚀就显得尤为重要。保护性耕作的推广应用为解决这个问题提供了一个很好的途径。内陆河流域的河西绿洲灌区保护性耕作对控制土壤风蚀起着多大的作用？相关研究很少，其机理还不是很清楚。为此，本项目以传统耕作为对照，对比分析该区保护性耕作下的土壤特性和风蚀特征，以及实施保护性耕作不同年限下土壤特性和农田风蚀特征的变化特点，进而分析作物残茬特性、土壤特性与农田风蚀特征的定量关系，探讨该区保护性耕作的防风蚀效应及其作用机制，为评估保护性耕作在防风蚀中的作用以及控制农田土壤风蚀采取合理有效的措施提供依据。

近十多年来，河西地区保护性耕作逐步应用，保护性耕作对该区防治土壤风蚀起着多大的作用？相关研究很少，其机理还不够清楚。本项目通过种植冬小麦田间试验，结合室内风洞实验，以传统耕作为对照，对比分析了河西地区保护性耕作下的风蚀特征和土壤特性，以及实施保护性耕作不同年限下土壤特性和农田风蚀特征的变化特点，进而分析农田风蚀特征与作物残茬特性、土壤特性的关系，探讨该区保护性耕作的防风蚀效应及其作用机制。研究结果表明：1）河西地区保护性耕作的防风蚀效应非常明显。与传统耕作相比，各保护性耕作措施0-30cm高度田间输沙量分别减少：免耕不覆盖17.4%-46.7%，免耕秸秆覆盖24.7%-45.2%，立茬24.7%-48.2%，残差压倒10.7%-42.4%；传统耕作田间风蚀深度为1.2-1.4mm，各保护性耕作田间风蚀深度均为零；保护性耕作的防风蚀效应立茬>免耕秸秆覆盖>免耕不覆盖>残差压倒；与传统耕作相比，保护性耕作田间风蚀物<0.1mm细颗粒占比较小，保护性耕作田间风蚀物有不至于在空气中传输很远的趋势。2）与传统耕作相比，保护性耕作地表粗糙度增大、近地面风速减小、土壤水分含量增加、紧实度增大。保护性耕作通过作物残茬改变地表覆盖状况，增加地表粗糙度，有效降低地表风速减少土壤风蚀；作物秸秆减缓地表水分蒸发，表层土壤含水量比传统耕作高，土壤抗风蚀能力增加；免耕保持了土壤结构不被破坏，并增加了表层土壤紧实度，从而增强土壤抗风蚀能力。3）保护性耕作与传统耕作>1mm土壤团聚体无显著差异；与传统耕作相比，保护性耕作土壤有机碳含量增加，<0.01分散性粘粒含量减少，土壤分散系数减小，稳定系数增加，土壤的微结构得到改善，保护性耕作朝着有利于增加土壤抗风蚀能力的方向发展，但这是个缓慢的过程，项目实施的短期内还不足以明显增加土壤抗风蚀能力。4）河西绿洲灌区保护性耕作对土壤理化性状总体上具有改善作用。随着保护性耕作年限的延长，土壤有机质、全N含量逐渐增加，而速效磷、pH呈降低的趋势。