蚯蚓深深地钻进底土.Earthworms burrow deep into the subsoil.进入底土的化学物质会减少，这对土质松软的热带土壤而言尤为重要。Less chemical gets into the sub-soil which is particularly important with the light, tropical soils.土壤中含有效锌转低时, 深层耕翻会使缺锌的底土暴露出来.In a solid ...

“底土”的英语可以翻译为：subsoil，substratum ...