New, prolonged release nitrogen fertilizers comprising metal-silicon-aluminum-oxygen-nitrogen system obtained by calcining mixture of natural materials, preferably clay and carbon, under nitrogen

摘要

New nitrogen fertilizers (I) consist of metal-silicon-aluminum-oxygen-nitrogen system (especially sialones, i.e. silicon aluminum oxynitrides) or mixtures containing these or similar phases. An Independent claim is also included for the preparation of (I).