SIGNIFICANCE OF HARVEST RESIDUES IN SUSTAINABLE MANAGEMENT OF ARABLE LAND I. DECOMPOSITION OF HARVEST RESIDUES

Harvest residues are parts of cultivated plants that remain on the plot after harvest or grazing. Decomposition of plant residues by microorganisms involves two simultaneous processes: mineralization and humification of carbon compounds. Decomposition processes depend on the type of plant residues, edaphic factors and residue management factors. Edaphic factors dominate in areas exposed to adverse weather conditions, while the type of plant residues largely plays the role of a regulator in favorable environmental conditions. Decomposition of plant residues takes place in two stages; phase I is relatively fast and depends on the initial nitrogen content, and phase II is relatively slow and is determined by the decomposition of lignins and phenols. In general, water-soluble fractions are degraded first, followed by structural polysaccharides, and finally lignin. Low winter temperatures and dry soil during the summer limit microbial decomposition, while microbial decomposition is greatest during the wet warm spring and autumn seasons.