If desired, certain nutri-' ents and minerals such as nitrates, urea, ammoniumsalts, phosphates, lime and the like may also be added at this time,'in accordance with knownpractice. i l i In `the past, it has been the practice for centuries to convert organic materials into soil fertilizersv by composting, the organic materials being inoculated with stable manure, fertil garden soil or other compo