compost; mixed soil
Refers to soil or growing medium prepared by blending various materials such as soil, sand, and organic matter for gardening or agriculture.
This compost is ideal for vegetable seedlings.
I bought some mixed soil at the gardening store.
培養土 is a type of 配合土 specifically formulated for cultivating plants, often with added nutrients and adjusted pH.
Compound of 配合 (blending, mixing) and 土 (soil). The term is straightforward and modern, with no obscure historical derivation.