surface soil

In loessal regions and alluvial valley fills of the western United States, both surface soil and subsoil are commonly friable.

西部黄土区和冲积河谷里，表土和底土一般是容易破碎的。

Based on the study of the mechanism of biotechnical slope protection,mechanical model were developed in the condition of surface soil reinforced with herb-root in geo-grid.

对土质路基边坡植被护坡机理分析的基上,给出了土工格室草本和木本植物根系加筋土体的力学模型。

The nutrient of C, N, P, K in rice straw buried by rotocultivator in deep soil layer released at a high rate and less remain than on surface soil.

运用机械将稻深施于水田土层，中的碳、氮、磷、钾养分释放比面施速率高，残留量少。