小麦留茬对陕北农田风蚀影响的室内风洞模拟

摘要

Standing stubble coverage is one of the efficient conservation tillage (CT) measures. It could reduce the wind erosion of topsoil of land through increasing terrain roughness (Z0) . Indoor wind tunnel simulation tests were conducted to measure and analyze the mass of wind erosion and structure of wind and sand flow on 2 kinds of soil in the Loess Plateau of northern Shaanxi Province with 3 heights of stubble and 2 widths of row space under 4 wind speeds of 6 m/s, 8 m/s, 10 m/s and 12 m/s. The results showed that, the mass of wind erosion of Aeolian Soil (AS) was much more than cultivated loessial soil (CLS)'s in the situation of bare soils. All kinds of heights of stubble could play a role in lessening the mass of the particles suspended in the air. Compared to the impact of stubble to AS, the impact of stubble had more effective manifestation to CLS under the same wind speed. With row space reducing to 15 cm from 20 cm, the inhibitory action increased, and the inhibitory action was more remarkable to CLS than AS. On the basis of elabora-tive analysis of spatial distributing structure of eroded particles, it was obvious that drifting sand flux of CLS with stubble mainly moved within 15 cm height of the ground surface, but drifting sand flux of AS floated primarily at 45 ~ 60 cm height. Increasing the stubble density on two kinds of soils could play an positive impact in decreasing the mass of wind erosion.%作为风蚀区主要保护性耕作措施之一,秸秆留茬覆盖可以通过增加地表粗糙度(Z0)减少近地表风速和侵蚀动力,并缩短风蚀颗粒的搬运距离和搬运高度,从而减少地表风蚀量.本研究采用室内模拟风洞实验,测定并分析了陕北2种主要土壤类型(风沙土和黄绵土)在4个风速、3种小麦留茬高度和2种留茬行距处理下土壤风蚀强度和在0～60 cm风洞断面风沙流结构.结果表明:当土壤表面裸露时,风沙土的风蚀量大于黄绵土；各种留茬高度都可以不同程度地减少土壤风蚀量,但相同风速时,留茬对黄绵土风蚀量的影响大于对风沙土的影响；行距由20 cm减到15 cm后,留茬对黄绵土风蚀表现的抑制作用强于对风沙土风蚀的抑制作用；对风沙流结构分析的结果是风沙土和黄绵土可蚀性颗粒分别集中在观测断面45～60 cm和0～ 15 cm高度范围内.留茬密度的增大对两种土壤风蚀的消弱存在明显正效应.