topsoil

The topsoil has been almost completely washed away.

表层土壤已差不多完全给冲走了。

According to scientists, it takes nature 500 years to create an inch of topsoil.

根据科学家们的看法，自然界要用500年的时间才能形成一英寸的表层土壤。

Straw mulching, cultivating and hoeing , regulating the root distribution in the topsoil are effective measures to reduce the soil evaporation.

秸秆覆盖、中耕锄划、调控表层土壤根系分布等可作为减少土壤蒸发的有效措施。