紫色丘陵区坡耕地生物埂的蓄水保土效应

Analysis on the Soil and Water Conservation Benefits of Four Bunds at Edges of Sloping Land in Purple Hilly Area

【目的】研究紫色丘陵区坡耕地生物埂的蓄水保土效应。【方法】采用土壤物理性质及土壤力学分析等综合性研究手段,对4种紫色丘陵区坡耕地生物埂措施的蓄水保土效应及其影响因素进行研究。【结果】(1)不同生物埂措施的土壤总孔隙度表现为桑树埂>花椒埂>紫花苜蓿埂>自然生草埂;生物埂土壤初始入渗率、稳定入渗率和平均入渗率变化趋势一致,依次为桑树埂>花椒埂>紫花苜蓿埂>自然生草埂。(2)生物埂土壤有效库容与对照自然生草埂相比差异明显(P<0.05),表现为木本埂>草埂>对照自然生草埂;在生物埂蓄水过程中,土壤的非毛管孔隙度和总孔隙度越大,土壤入渗性能越好,土壤水库库容越大;生物埂土壤容重越大,则土壤渗透性和通透性越差,导致土壤无效库容越大,坡耕地农作物水分利用困难。(3)生物埂土壤抗剪强度表现为紫花苜蓿埂(0.38 kg·cm-2)>花椒埂(0.25 kg·cm-2)>桑树埂(0.22 kg·cm-2)>自然生草埂(0.18 kg·cm-2),内摩擦角以花椒埂最大(20.76°);生物埂土壤内摩擦角与机械组成分形维数、土壤初始含水率之间呈显著负相关,与微团聚体分形维数呈显著正相关;土壤黏聚力和抗剪强度与机械组成分形维数呈显著负相关,与土壤分散率呈显著正相关,与微团聚体分形维数相关性不显著。【结论】由于紫色丘陵区生物埂措施对土壤孔隙结构等物理性质具有改良作用,提高了土壤有效库容,这对抵御坡耕地季节性干旱作用成效明显;同时也增强了土壤抗剪强度,使得地埂抵抗降雨和径流剪切的能力增强,保证了坡耕地土地生产力的稳定。

【Objective】 The article aimed to study the soil and water conservation benefits of four bunds at edges of sloping land in purple hilly area. 【Method】 A systematic analysis of the soil and water conservation benefits and its influencing factors of various bunds was made through such comprehensive research approaches as soil physical and mechanical properties analysis and so on. 【Result】 Soil total porosity of different bunds planted with vegetation were shown as mulberry＞prickly ash＞alfalfa＞natural grass; a similar varying trends of initial infiltration rate, final infiltration rate and mean infiltration rate for each kind of bund existed, which showing a trend of mulberry＞prickly ash＞alfalfa＞natural grass. Soil available water storage of all bunds was obviously different （P＜0.05） from natural grass, which presented as the bund planted with tree＞grass＞natural grass. During the process of water storage for all bunds, the higher the soil non-capillary porosity and soil total porosity was, the better the soil infiltration capacity could be. The larger the soil bulk density was, the worse soil infiltration capability and soil perviousness would be, which leading to larger unavailable soil reservoir, and also making it is difficult for crops on sloping lands to absorb soil water. Soil shear strength of all bunds was in the order as alfalfa （0.38 kg？cm-2）＞prickly ash （0.25 kg？cm-2）＞mulberry （0.22 kg？cm-2）＞natural grass （0.18 kg？cm-2）, and internal friction angle of the bunds of prickly ash was the biggest（20.76°）among these bunds. The internal friction angle of all bunds had a significant negative correlation with fractal dimension of particle size distribution, initial water content of soil, while it had a significant positive correlation with fractal dimension of aggregate size distribution. However, soil cohesion and shear strength had a significant negative correlation with fractal dimension of particle size distribution and a significant positive correlation with soil dispersion, but soil cohesion and shear strength did not correlate significantly with fractal dimension of aggregate size distribution. 【Conclusion】 All bunds in purple hilly area improved the available soil reservoir by the way of improving soil physical properties such as soil pore structure and so on, which preventing sloping land from the damage of local seasonal drought. Moreover, the bunds also enhanced the soil shear strength and the ability of resistance to rainfall and runoff erosion, which obviously ensuring the stable productivity of sloping land in purple hilly area