利用黑土层厚度评价东北黑土区土壤生产力--以鹤北小流域为例

Productivity Assessment for Black Soil Region in Northeastern China Using Black Soil Thickness——A Case Study of Hebei Watershed

东北黑土区是中国重要的粮食生产基地,自开垦以来,土壤生产力退化严重。探索简易可行的黑土生产力评价方法,可为合理利用和保护黑土资源提供科学依据。以位于典型黑土区北端的鹤北小流域为例,基于黑土厚度和土壤理化性质的野外调查,构建了用黑土层厚度评价土壤生产力的方法。结果表明,黑土层厚度与土壤生产力水平间呈对数关系,当黑土厚度小于40—50cm时,随着厚度增加,土壤生产力增加明显;当黑土厚度大于40—50cm时,随厚度增加土壤生产力增加速度减缓。多年大豆单产及当地土地分等定级的双重验证表明用黑土层厚度评价土壤生产力简易可行,能够揭示土壤生产力的空间分异。研究区耕作方式对土壤生产力影响显著:同一地块内从坡顶到坡脚生产力呈增加趋势,但在等高种植情况下,地块土壤生产力差异较小,顺坡或与等高线交叉情况下,地块土壤生产力差异较大。

The northeast black soil region, an important grain production area in China, is suffering from serious productivity degradation since long term conventional cultivation. It is helpful to develop an easy and practical productivity assessment method for black soil resources conservation. Soil samples were taken and analyzed for selected fields in the Hebei watershed, located in the north part of typical black soil region of Northeastern China. The quantitative relationship between top soil thickness and soil productivity was established and applied to assess soil productivity. Results showed that there was a logarithmic relationship between top soil thickness and soil productivity, which increased with increasing soil depth. However, the increasing rate varied and the rate was faster for soils at depth less than 40--50 cm than that at depth greater than 40--50 cm. Both long-term soybean yield and local land quality classing certified the rationality of the method, especially for assessing the spatial variation of soil productivity. In the studied watershed, tillage had significantly effects on the spatial distribution of soil productivity, which increased from slope top to toe generally. However, little variation existed within the field for contour cultivated fields, but obvious difference existed for up-down slope cultivated fields. It is necessary to practice conservation tillage.