湘中紫色土丘岗区水土流失规律及土壤允许侵蚀量的研究

Research on the Rule of Soil Erosion and Allowable Eroding Amount in the Purple Soil Upland of the Middle Part of Hunan Province

自1988～2003年,在湖南省衡南县谭子山镇坡度5～20°的石灰性紫色土丘岗地上进行了水土流失的定位观察。结果表明:水土流失与坡度、植被覆盖度及开发利用模式关系甚为密切。土壤侵蚀量随坡度增大而增大,坡度每增加1°,土壤侵蚀量年递增730～930t/km2,坡度与土壤侵蚀量呈极显著正相关。植被覆盖度每增加1%,土壤侵蚀量则减少60～100t/km2,土壤侵蚀量与植被覆盖度呈极显著负相关。等高作梯的旱耕地和园地土壤侵蚀量仅为顺坡直耕的旱耕地和园地顺坡的1/3左右;旱耕地、园地等高开垦的强度大,开垦之后1～2年土壤侵蚀量成倍增长;从水土保持角度看,林地乔、灌、草结合模式最好,裸地植草模式次之。应用土壤肥力平衡理论,选取化学退化主导指标N元素,并以石灰性紫色土恢复生态时土壤N1.5g/kg为临界,与成土速度综合考虑,进行紫色土坡地土壤允许侵蚀量的研究,首次提出石灰性紫色土丘岗坡地土壤允许侵蚀量为每年170t/km2。

From 1998 to 2003,the lime purple soil upland of 5～20° be made a reservation to observe soil erosion in Tanzishan town of Hengnan county of Hunan Province.The result indicate: a close relation is among soil erosion,gradient,coverage rate of the vegetation and soil exploitation mode.The soil eroding amount increase with the gradient.The gradient increases 1°each time,the soil eroding amount increase 730～930 t/km^2,the gradient and the soil eroding amount are notable positive correlation.The coverage rate of the vegetation increases 1% each time,the soil eroding amount decreases 60～100 t/km^2,the coverage rate of the vegetation and the soil eroding amount are notable negative correlation.In the dry land and garden plot,the soil eroding amount of terraced fields is only 1/3 of that be ploughed directly along the slope.It is difficult that assart along the contour in the dry land and garden plot,after the first 1～2 years,the soil eroding amount will increase at double.From the soil and water conservation point of view,the mode that integrates arbor,shrub and grass in woodland is the best,the mode that plants grass in bare land is the second.The theory on soil fertility balance is applied,nitrogen element that is dominant factor of soil degradation on chemistry,and nitrogen element 1.5 g/kg is taken as critical when ecology be resume in the lime purple soil upland.On this basis,the allowable eroding amount in purple soil upland is researched,and it is put forward that the soil eroding amount is 150 t/km^2 per year in the lime purple soil upland.