A New Index of Organic Matter Stability

Abstract

A new organic matter stability index (S.I.) has been developed determining the humic acid content in samples of compost, both as they stand and when subjected to treatment with apolar and polar solvents and acid hydrolyses for the purpose of eliminating substances (pseudo-humic substances) that interfere with analytical determination of the same. The index, which registers values between zero and one, easily relates to the degree of stability and maturity of organic matter. Checks on the reliability of the index when applied to 10 different types of organic matrices have confirmed its usefulness for direct measurement of the degree of stability (SI > 0.6) and maturity (SI > 0.8) of organic matter, as well as the effectiveness of the analytical method proposed for determining the humified fraction content in organic matter, as a means of obtaining more realistic values, especially in the case of immature substrates.