Decomposition and nutrient release patterns of the leaf biomass of the wild sunflower (Tithonia diversifolia): a comparative study with four leguminous agroforestry species

The selection and use of appropriate plant materials to maintain a sufficiently high nutrient supply to meet crop needs remains a major challenge of nutrient management under low input systems. Therefore, research on plant biomass quality as it relates to decomposition and nutrient release has become imperative. This research was conducted at the Agroforestry Research Station of the Kwame Nkrumah University of Science and Technology, Kumasi, Ghana to determine the decomposition and nutrient release patterns of Tithonia diversifolia, a rarely used non-traditional species but of research interest in soil fertility improvement practices in Ghana. The decomposition and nutrient release patterns of T. diversifolia was compared with Senna spectabilis, Gliricidia sepium, Leucaena leucocephala and Acacia auriculiformis which are commonly used in biomass transfer systems. Results of the study confirmed significantly high N, P, K concentrations in T. diversifolia comparable to levels recorded for the four leguminous species. In addition, T. diversifolia recorded the highest percent decomposition and nutrient release rates which differed significantly (P < 0.05) from rates of the four leguminous species. It was apparent from the study that decomposition and nutrient release rates of species are related to quality of leaf material. Phosphorus and Mg concentration in particular were most influential in decomposition and nutrient release based on significant results. For this reason, it would be imperative to consider the concentrations of P and Mg among other factors in selecting high quality plant materials for green manuring.