let a mulch top of the soil

例句：

1. 1. The soil was covered with a thick layer of grass.
   土壤上覆盖着厚厚的一层草。
2. 2. The gardener used mulch to suppress weeds and improve soil quality.
   园丁使用覆盖物来抑制杂草并改善土壤质量。
3. 3. The farmer spread manure on the field as a natural mulch.
   农民在田地上撒施粪肥作为天然的覆盖物。