PURPOSE: To obtain a new culture soil having excellent water retention and permeability and capable of imparting slow releasability to fertilizing components without compounding the soil with any material and produced in a short time at a low cost

CONSTITUTION: This culture soil is composed of reactional products of a solid- liquid mixture of decomposable wastes with calcium oxide. A part of the calcium oxide fixes, as calcium salts, acids consisting of low fatty acids, e.g. formic acid produced from amino acids of the decomposable waste by thermal decomposition caused by the reaction and acids consisting of amino acid and low fatty acids, e.g. formic acid originally contained in the decomposable waste. The remaining part of the calcium oxide is changed to calcium carbonate. A portion of the organic matter is not fixed as calcium salt and exists as free organic components in the culture soil.