沟蚀发育的黄土坡面上秸秆覆盖防蚀效果研究

为评价玉米秸秆这一廉价资源的防蚀效果,利用人工模拟降雨试验,研究在黄土高原典型高强度侵蚀性降雨条件下,不同玉米秸秆覆盖方式(沟头缓冲带覆盖、沟内填充覆盖)及其组合对沟蚀发育黄土坡面侵蚀的防治效果。结果表明,对于有细沟和浅沟发育的黄土坡面,不同方式秸秆覆盖可减少坡面侵蚀量8.3%~46.2%,降低径流含沙浓度19.1%~49.6%。其中浅沟沟头覆盖+浅沟侵蚀带沟道全覆盖(H+G)和浅沟沟头覆盖+浅沟侵蚀带主沟道覆盖+细沟沟头覆盖(H+MG+RH)2个处理的防蚀效果最佳,二者分别减少坡面侵蚀量45.0%和46.2%。秸秆覆盖通过改变坡面径流与侵蚀产沙量的关系而非减少径流量来减少坡面侵蚀量。不同方式的秸秆覆盖均可降低径流流速、减弱径流挟沙能力以及径流侵蚀力,进而减少坡面侵蚀量,其中,浅沟沟头秸秆缓冲带覆盖和浅沟沟槽内秸秆填充覆盖均可减小流速42.6%以上。比较2种覆盖方式,沟头缓冲带覆盖较沟内填充覆盖在减少侵蚀方面更有效。因此,在沟蚀发育的黄土坡面上,用玉米秸秆缓冲带覆盖侵蚀活跃的沟头部位可达到最优的防蚀效果。

Erosion Control Effects of Cornstalk Mulching on Loess Hillslope with Gully

Active-stage gully erosion processes can result in steep rise of sediment yield, thus seeking effective ways has important implications for the prevention of slope gully erosion. To quantitatively evaluate the cornstalk mulching effects on controlling soil erosion on loess hillslope with gully, a series of artificial simulated rainfall experiments were conducted to study the effects of different combinations of cornstalk mulching positions (one was whole plant buffer mulching on the head of the gully and the other was filling the gully with clipped short cornstalk) on the gully erosion on loess hillslope under the typical high intensity erosive rainfall (on the Loess Plateau) condition. The results showed that the runoff amount was reduced by 7.2%~13.8%, while the sediment yield and the average runoff sediment concentration were reduced by 8.3%~46.2% and 19.1%~49.6%, respectively. Treatment H+G (ephemeral gully head + all gully covered) and H+MG+RH (ephemeral gully head + main gully + rill head covered) got the best effect with reductions of 45.0% and 46.2% in reducing slope sediment yield, respectively. It was obvious that cornstalk mulching reduced sediment yield by changing the runoff-sediment relationship instead of reducing the runoff amount. The whole plant buffer mulching on the gully head was more effective between two mulching positions. Cornstalk mulching on different positions can reduce the channel runoff velocity, sediment transport capacity as well as runoff erosivity, which was meaningful for reducing soil erosion. For example, cornstalk buffer mulching on gully head and filling gully can both reduce the runoff velocity more than 42.6%. As a result, once gullies appeared on the loess hillslope, cornstalk mulching on active-stage gully head would be the best way to control gully erosion. Much better effects can be exhibited when gully itself was mulched with clipped short cornstalk at the same time.