【摘要】 土壤侵蚀是导致坡耕地耕层质量退化和土壤生产力不稳定的关键驱动因素。该文从水蚀区坡耕地侵蚀控制和生产功能角度,在解析地块尺度土壤侵蚀、水土保持、农业活动对坡耕地耕层生态过程作用特征的基础上,系统分析了土壤侵蚀对坡耕地耕层质量退化作用、影响效应及作用途径。认为:1)坡耕地耕层质量变化由降雨侵蚀、耕作活动交互作用的生态过程决定,2种作用的时间、空间尺度不同;耕层土壤参数在坡耕地农业生产中作用分为保水、保土、保肥和增产潜力,由地块尺度农作物-耕层耦合效应决定土壤生产能力、坡耕地水土流失特征及耕层侵蚀性退化方向及程度。2)土壤侵蚀对坡耕地耕层质量退化作用表现为土壤性质恶化、土壤质量劣化、土地生产力衰退3个方面,耕层土壤物理性质变异程度大于化学性质变异,径流作用导致的土地生产力衰退大于土壤流失作用。3)坡耕地耕层质量评价指标体系应兼顾侵蚀下降、产量提升2个目标,地块尺度诊断指标有效土层厚度、耕层厚度、土壤容重、土壤抗剪强度、土壤有机质、土壤渗透性可作为合理耕层评价最小数据集;坡耕地合理耕层适宜性分为5级,其诊断指标分级标准宜与土壤侵蚀分级和耕地地力分级衔接。4)坡耕地合理耕层评价未来应密切关注耕层质量诊断指标最小数据集、坡耕地合理耕层阈值/适宜值分级标准、坡耕地水土流失阻控标准拟定3个主要方向。研究可为深入认识坡耕地侵蚀性退化机制,辨识坡耕地合理耕层调控途径以及坡耕地合理耕层构建技术参数提供依据。更多还原

【Abstract】 Soil erosion is the key driving force that causes tillage-layer quality degradation gradually and soil productivity variation precariously in sloping farmland. According to 2 functions of tillage-layer, erosion control and soil productivity, in this paper, we firstly focused on the ecological processes occurring in tillage-layer of farmland under the comprehensive interactions among soil erosion, soil and water conservation practices and agricultural activities at plot scale, and further summarized its influencing roads of soil erosion on tillage-layer quality. Results showed that: 1) Tillage-layer quality of sloping farmland was determined by the 2 ecological interaction process, rainfall erosion and tillage activities, and the temporal and spatial scales of these interaction on tillage-layer quality were very different. Soil properties functions indicating tillage-layer quality of slope farmland could be divided into such 4 types as water conservation, soil conservation, fertilizer conservation and production potential during a total agricultural production process. Crop-tillage coupling coordination could determine such characteristics of slope farmland as soil productivity, soil and water loss and the degradation direction & degree of tillage-layer caused by water erosion. 2) Tillage-layer quality was the characteristics of soil quality, its vertical combination along the active layer of crop root-system and underlying layer along the soil profile and the site conditions of sloping farmland. Tillage profile configuration of sloping farmland was the vertical distribution characteristics of soil texture, soil bulk density, soil porosity and soil mechanical resistance, so did its combination characteristics. The changes of tillage-layer quality of sloping farmland had obvious cumulative effects of water erosion on tillage disturbance. Degradation effects by water erosion on tillage-layer quality of sloping farmland were manifested in 3 aspects: deterioration of soil properties, deterioration of soil quality and decline of land productivity. The variation degree of soil physical properties was greater than that of chemical properties, and the decline of land productivity caused by runoff was greater than that caused by soil erosion. The change of crop yield had a significant hysteresis effect compared with soil quality degradation, meanwhile, soil permeability and soil erosion sensitivity had a direct correlation to the sustainable and stable productivity of sloping farmland. 3) In primary water erosion areas of China, an unified minimum data set of tillage-layer quality evaluation of sloping farmland should be set up aimed at the typical soil types and farming systems, which paid more close attention to the 2 functions of tillage-layer on erosion reduction and yield increase simultaneously. Such soil parameters as effective soil layer thickness, tillage layer thickness, soil bulk density, soil shear strength, soil organic matter and soil permeability could be included into the minimum data set for rational tillage-layer evaluation at plot scale. The time response characteristics of the minimum data set of tillage-layer quality should be fully taken into account in determining the threshold/suitable value. Rational tillage suitability of sloping farmland was divided into 5 grades, which were connected with soil erosion classification and cultivated land fertility classification. 4) Tillage-layer evaluation of slope farmland should focus on 3 aspects in the future, minimum data set of diagnosis index for tillage-layer quality, classification criteria of rational tillage threshold/suitable value and criterion of soil erosion control on sloping farmland. Accompanied by such normal indicators as soil erosion modulus, runoff coefficient and soil loss tolerance for protection of sloping farmland, the minimum data set index for diagnosing tillage-layer quality, as soil organic matter, soil infiltration, soil clay content could provide quantitatively a regional early-warning standards, which would benefit to more efficient soil and water loss control and realize sustainable utilization of sloping farmland These viewpoints were helpful in understanding the mechanism of degradation process caused by erosion of sloping farmland, and identifying quantitatively regulation approaches for rational cultivated-layer of sloping farmland, and also could provide some technical parameters for constructing rational tillage layer of slope farmland in water erosion area.更多还原