泥土 (nítǔ) is a general, everyday term for soil, earth, mud, or clay — the natural material you might garden with or find on the ground. It is less formal than 土壤 (tǔrǎng, the scientific 'soil'), broader than 泥 (ní 'wet mud'), and more concrete than 土 (tǔ) which also means 'earth' but has additional senses like 'local' or 'rustic'.