Decomposition of coffee residue in soil

Abstract In this study the changes in the chemical properties of coffee residue during decomposition in soil were investigated. 1) Coffee residue contained about 20 g kg-1 N. The main N compound was a structural protein-No However, the content of easily decomposable N (soluble protein-N and nonprotein-N) extracted by 800 mL L-1 ethanol and 0.1 mol L-1 phosphate buffer (pH 7.5) was very low. 2) The rates of nonprotein-N and soluble protein-N which remained reached values of 59 and 66% at 314 d after application of the coffee residue (DAA) to soil, respectively. However, the amount of structural protein-N reached a value of 96% at 314 DAA. 3) The lipid fraction of the coffee residue decreased from 186 to 47 g kg-1 by 314 d after application. Coffee residue has a high content of lipid fraction and a large fraction corresponding to structural protein-No Therefore, the decomposition of the coffee residue is slower than that of other organic materials.