Measurement of decomposition and associated nutrient release from barrel medic (Medicago truncatula) hay and chickpea (Cicer arietinum) straw using an in vitro perfusion system

Two in vitro laboratory experiments were conducted to evaluate the effects of nutrient additions, soil inoculation, and sampling times on the decomposition rates and nutrient release patterns of leguminous crop residues. Cumulative CO2 evolution and the percentage nutrient release from barrel medic hay (Medicago truncatula) and chickpea straw (Cicer arietinum) were determined over a 6-week period using a 0.005 M CaCl2 recycling system (UNE in vitro perfusion apparatus). The decomposition study was carried out at 25˚C in a controlled temperature laboratory. There were no significant differences between the decomposition rates of the 2 residues. The percentage C release was not significantly affected by nutrient addition or by soil inoculation. More than 50% of the total C that was released from the residues occurred in the first 7 days with peak release at 3–4 days. Because of an accumulation of nutrients in a muscilaginous substance in the apparatus, and adsorption of P to the plastic, it was not possible to measure the release of nutrients from the residues by sampling the perfusion solution. This had to be achieved by direct measurement of loss of nutrients from the residues. Except for K, the nutrient released from residues was not affected by residue or sampling time. <keyword>Additional keywords: organic matter, mineralisation, nutrients.</keyword>