Is the Alkalinity within Agricultural Residues Soluble

A laboratory experiment was carried out to determine the contribution of whole residues of canola, chickpea and wheat and their fractions (insoluble/soluble) to soil pH changes during a 14-day incubation. Residues were added (1% w/w) to Frankston and Shepparton soils of initial pH of 4.45 and 6.20, respectively. Increases in pH were greatest for chickpea, less for canola and the least for wheat. The experiment confirmed that the soluble fraction of residues is important for the alkalinity release within initial stages of decomposition and also the source of components responsible for pH decreases in subsequent incubation. However, the relative differences of whole residues and the fractions were influenced by the initial soil pH.