Abstract: A process for the ammoniation of straw and other plant materials containing lignocellulose with a dry matter content of at least 60%, utilizing anhydrous ammonia, preferably in liquid form. The plant material is covered by a gas impervious material and ammonia is added in excess of the amount needed for optimal irreversible nitrogen binding, preferably from 20-35 kg NH.sub.3 /ton dry matter, without application of external heat and pressure. The ammonia impregnated material is left at ambient temperature for at least 10 days, whereafter it is vented and ready for use. The preferred use of the ammoniated straw is as an animal feed.