Surface should be treated as a key technology for conservation tillage. 表土耕作应该作为保护性耕作的一项关键技术。
The runoff sediment has higher clay content than the surface soil, andthe splash soil has higher fine sand content. 通过对侵蚀上壤的颗粒组成分析表明，侵蚀对土壤颗粒具有选择性，径流侵蚀泥沙中粘粒含量比侵蚀表土含量高，溅蚀泥沙中细沙粒含量变高。
美
