东北薄层黑土区作物轮作防治坡面侵蚀的效果与C值研究

作物轮作通过影响通用土壤流失方程(USLE)中作物覆盖和管理因子C值的变化和改良土壤性质而减少坡面土壤侵蚀。基于东北薄层黑土区连续6年大豆—红小豆轮作和裸露休闲坡面小区的径流泥沙和降雨资料,分析了2011—2016年研究区侵蚀性降雨特征,探讨了作物轮作防治坡面土壤侵蚀的效果,研究了作物轮作C值的年内和年际动态变化。结果表明:研究区所有侵蚀性降雨皆发生在5—10月,其降雨量占全年降水量的32.5%～68.1%,且年内和年际分布不均。对于5°坡度的裸露小区,土壤侵蚀主要发生在6—8月,坡面径流量和土壤流失量分别为48.4mm和1 388.2t/(km~2·a);对于5°坡度的作物轮作小区,土壤侵蚀主要发生在5—7月,坡面径流量和土壤流失量分别为19.5mm和166.7t/(km~2·a)。与裸露休闲小区相比,作物轮作小区可使黑土坡面年径流量和土壤流失量减少59.7%和88.0%。大豆—红小豆轮作措施的多年平均C值为0.12,其中大豆作物的C值为0.04,变化范围0.007～0.080;红小豆作物的C值为0.38,变化范围0.28～0.46。大豆和红小豆作物的C值月变化分别为0.01～0.24和0.01～0.80,呈先减少后增加的变化趋势。大豆—红小豆轮作对东北薄层黑土区坡面土壤侵蚀防治有明显效果,研究结果可为薄层黑土区土壤侵蚀定量评价和预报模型的建立提供基础数据。

Effects of Crop Rotation on Preventing Hillslope Soil Erosion and Its C Factor's Variation in Thin Layer Mollisol Region of the Northeast China

Crop rotation affects dynamic changes of C factor in USLE and reduces hillslope soil erosion by improving soil properties. Based on six years observation data of runoff, soil loss and rainfall from the soybean-red adzuki bean rotation and bare-fallow runoff plots in the thin layer Mollisol region of the Northeast China, this paper analyzed erosive rainfall characteristics, discussed effects of crop rotation on preventing hillslope soil erosion, and explored yearly and monthly changes (May-October) of C factor (crop cover and management) during 2011-2016. The results showed that all erosive rainfall in the study area occurred from May to October, which occupied 32.5% to 68.1% of annual precipitation, and its distribution of inter-annual was uneven. For the bare-fallow runoff plot with 5° slope gradient, soil erosion mainly occurred in June to August and annual runoff and soil loss was 48.4 mm and 1 388.2 t/(km²·a) respectively; while for the crop rotation plot with 5° slope gradient, soil erosion mainly occurred in May to July and annual runoff and soil loss was 19.5 mm and 166.7 t/(km²·a) respectively. Compared with the bare-fallow plots, average annual runoff and soil loss from crop rotation plot under 5° slope gradient were decreased by 59.7% and 88.0%, respectively. Average yearly C value for crop rotation plots was 0.12. For soybean crop, C value was 0.04, ranging from 0.007 to 0.080; and for red adzuki bean, C value was 0.38, ranging from 0.28 to 0.46. Monthly C values of soybean and red adzuki bean varied between 0.01~0.24 and 0.01~0.80, respectively. The soybean-red adzuki bean rotation had a significant effect on preventing hillslope soil erosion in the thin layer Mollisol region of the Northeast China. The results provided scientific basis for quantitative evaluation of soil erosion and prediction model establishment in thin layer Mollisol region of the Northeast China.