黑土开垦之前黑土层厚度一般为30～50cm,有的可达1m,开垦之后,黑土层厚度总的趋势是变薄,但仍以中等厚度(30～60cm)占多数。变薄的原因有土壤自然沉实和土壤侵蚀两个方面,前者是由生土变熟土的必然过程,后者可通过保护性耕作措施加以防治。 Before reclamation of black soil, the thickness of black soil is generally 30-50cm, and some up to 1m. After reclamation, the general trend of black soil thickness is thinning, but it still takes the medium thickness (30-60cm). The reason for the thinning is that the soil is naturally solidified and the soil is eroded. The former is an inevitable process of soil preparation and soil amendment, and the latter can be controlled by conservation tillage.