मृत्काष्ठकोष्ठाः स्नेहस्य पृथिवी लवणस्य च ॥ कZ_०२.१५.६४च्द् ॥
mṛt-kāṣṭha-koṣṭhāḥ snehasya pṛthivī lavaṇasya ca
Oils/fats (sneha) shall be stored in earthen or wooden containers; salt shall be stored in contact with earth (ground storage).
Because preservation depends on material compatibility: oils keep better in suitable containers, while salt is stabilized by dry ground storage.