金沙江干热河谷坡改梯对水土保持的影响

Effect of Terracing Slope Cropland on Soil and Water Conservation in Dry-hot Valley of Jinsha River Basin, Southwest China

【目的】以金沙江下游干热河谷实验区不同修筑年限、种植不同作物的梯田与坡耕地为研究对象,探讨坡改梯的水土保持效益,筛选和提炼金沙江下游干热河谷梯田农业生态利用模式。【方法】分析新修梯田、老梯田和坡耕地的土壤基本物理性质、团聚体分布特征及土壤养分元素等指标,结合微型径流小区观测。【结果】坡耕地改为梯田之后,尽管梯田减流与减沙效果明显,可达30%以上,但因人为扰动以及梯田修筑过程技术不规范等,导致新修梯田土壤的基本物理性质和主要养分含量与坡耕地土壤无显著差异,甚至个别指标有所下降。而较于新修梯田和坡耕地,10年以上老梯田土壤容重显著下降,土壤有机质、全氮、全磷以及水解氮等含量显著上升,土壤结构体数量增加。【结论】坡改梯在长期实行后,其在固土保水、提高土壤质量等效益会十分显著。

【Objective】Based on terracing slope croplands with different construction years and plants in the Lower Reaches of Jinsha River,the agro-ecological utilization modes of terracing on soil and water conservation were screened and summarized.【Method】The indices including fundamental physical properties,soil aggregates and nutrients associated with runoff micro-plots were used to evaluate the effects of terracing construction in newly-built terraces,early-built terraces(over a decade)and slope croplands.【Result】Despite the reduction of runoff and sediment yield over 30%in newly-built terraces relative to slope croplands,the difference of fundamental physical properties and major nutrients in soils between new-built terrace and slope croplands was insignificant,and several indices of newly-built terraces in soils even decreased compared with the latter due to artificial disturbance and non-standard terrace construction process.However,soil bulk density was significantly lower while the contents of soil organic matter,total nitrogen,total phosphorus,hydrolyzed nitrogen and peds in early-built terraces were significantly higher than that in newly-built terraces and slope croplands.【Conclusion】The long-term benefit of terracing slope cropland in soil and water conservation as well as soil quality improvement should be significant.