The objective of this study was to measure the speed of decomposition and nutrient release in situ from residues of common bean (Phaseolus vulgaris L.) crop. In field conditions, leaves of common bean cultivars senesced during the growth cycle and stems and podwalls after pod threshing were collected. These residues contained 2.3 Mg ha-1 of mass, 31 kg ha-1 of N and 2.4 kg ha-1 of P that corresponded to 63, 41 and 28 % of total mass, N and P, respectively accumulated during the crop growth cycle. Two experiments were conducted, during winter-spring and spring-summer. Stems, podwalls and senesced leaves were placed separately in litterbags on the ground and collected, from the 2nd to the 120th day. The dry matter and nutrient amounts found in each residue type were adjusted to a simple exponential model. The half-life of the residues was, in the first and second trial respectively, 133 and 179 days for stems, 70 and 80 days for leaves, and 64 days for podwalls. The relatively slow residue decomposition may be associated with the high C:N ratio (C:N > 60 in stems and podwalls). Nitrogen and P release by residues was similar to the decomposition pattern, while K release was faster. The results indicate that senescent leaves and residues produced after pod threshing can cover part of the nutrient demand of common bean crop, which is relevant for sustainable agricultural systems.
organic matter; nutrient cycling; Phaseolus vulgaris
