Phosphorus dynamics in the litter layers of a traditional slash-mulch bean production system in southern Costa Rica : reassessing concepts and methods in litter decomposition research

A major portion of the beans consumed in Costa Rica are produced under a traditional slash-mulch system referred to as frijol tapado. Research is under way to assess the possibility of improving yields and sustainability of the system through fallow enrichment with typical agroforestry tree species. Selecting appropriate mulch-providing species for use in this and other agroforestry systems requires detailed knowledge of their nutrient-release behavior during decomposition. Standard decomposition and nutrient release models are of little use in this context because (1) they assume (usually implicitly) that all litter is in direct and continuous contact with the soil solution and (2) they do not reflect the fact that nutrients flow into and out of the litter simultaneously along different paths (Berg 1988) and, as a consequence, net change in litter nutrient content does not necessarily correspond to nutrient availability in the litter layers and maybe even the soil.