DECOMPOSITION AND NITROGEN RELEASE PATTERNS OF TREE PRUNINGS AND LITTER

Many studies have shown that agroforestry tree prunings can supply suf ficient nutrients to meet crop demand, with the exception of phosphoru s. The potential of these organic inputs to supply nutrients depends o n their resource quality. Various indices have been developed to predi ct decomposition and nitrogen release patterns of tree prunings. To da te the (lignin + polyphenol):N ratio seems to be the most robust ratio for predicting mass loss and nitrogen release. However, no critical v alue can be given because of the different methods used to analyze pol yphenols. Suggested areas of future research include development of ro bust indices for predicting plant litter quality, decomposition patter ns of belowground litter (roots), residual effects of tree biomass add itions, and effects of adding mixtures of organic materials of contras ting quality. The overall challenge is to develop ways of managing org anic matter decomposition to optimize short-and long-term release of n utrients and the maintenance of soil organic matter.