Decomposition of coffee residue in soil

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.