黑土侵蚀速率及其对土壤质量的影响

Study on black soil erosion rate and the transformation of soil quality influenced by erosion

利用137Cs示踪法,研究了东北黑土耕作土壤的流失厚度和速率,探讨了水土流失对土壤机械组成、有机质、土壤水分、容重及其N、P含量的影响。结果表明:研究区侵蚀坡面137Cs的分布深度在0～25cm,137Cs的活度在1246.05±85.90～1499.45±101.73Bq/m2,侵蚀厚度可达0.316～0.433mm/a,侵蚀强度3033.6～3940.3t/km2·a,已属于中度侵蚀水平。水土流失造成土壤质地粗化,从坡顶向坡底,耕层土壤有机质增加、容重变化不大,含水量增加,土壤养分的“贫化”现象明显。

The paper investigates the distribution depth of cesium-137 and erosion rate of black soil using cesium-137 tracer, discusses the influence of soil erosion on the contents of particle size, organic matter, specific gravity and water quantity, nitrogen and phosphorus in the tillage layer of 0-20 cm on a typical slope. Cesium-137 activities in the profile,mainly distributed in the layer of 0-25 cm deep, are in the range of 1246.05±85.90 Bq/m^2 to 1499.45±101.73 Bq/m^2. So,the annual soil erosion rates can reach 3033.6-3940.3t/km^2 within the last 40 years,which have reached the moderate erosion level. It is the right time to pay enough attention to the black soil erosion. Also, it is completely feasible to investigate the erosion rate of black soil using cesium-137 tracer method. The slope length and gradient have distinctly effects on soil erosion intensity. The trend that the soil particles are becoming increasingly coarser is also obvious. The percentage of sand and clay declines gradually, and silty sand increases from top down to bottom of the slope. Moreover, organic matter （OM） is also in the trend of increase from top to bottom of the slope, but the contents of OM in both erosion and sedi mentation profile （2.56-3.10%） are markedly lower than that in original black soil. The specific gravity increases and water content declines in the erosion profile. Furthermore, the phenomenon that the contents of nitrogen and phosphorus decline is clear. Both of the quick degradation of black soil quality and agricultural non-point source pollution should be paid attention to by all circles. Due to the geographical location of black soil belt and its relative location to Pacific and Eurasia, both of frequency and intensity of wind taking place in spring every year are high. So, the above-mentioned soil erosion intensity is the result of wind erosion and water erosion. The percentage of soil quality degradation induced by water erosion and flux of main agricultural non-point source pollutants should be further studied.