Biochemical Fractionation of Soil Organic Matter after Incorporation of Organic Residues

Abstract

Soil organic matter (SOM) is a key factor for building and maintaining soil quality. The SOM quality is commonly assessed using densitometric and sieving separation methods, but such methods do not inform on the biochemical composition of SOM. Our objective was to evaluate the van Soest extraction procedure for soluble (SOL), holocellulose (HOLO) and lignin/cutin (LIC) fractions of SOM after incorporating crop residues and animal wastes into a C-depleted loamy sand. Millet cuttings, oat straw, fresh cattle manure and cattle manure compost were dried, sieved to obtain 53 - 250 and 250 - 2000 µm size fractions and characterized biochemically using a modified NDF-ADF-ADL van Soest method. Soil was also sieved into 53 - 250 and 250 - 2000 µm fractions. On a dry mass basis, crop residues contained 60% - 70% holocellulose while animal wastes contained more than 40% ash.