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

美国西部黄区和冲积河谷里，表和底一般是容易破碎的。

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.

质路边坡被护坡机理分析的础上,给出了工格室内草和木根系加筋体的力学模型。

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.

运用机械将稻秸秆深施于水田层内，秸秆中的碳、氮、磷、钾养分释放比秸秆面施速率高，残留量少。