Organic inputs for soil fertility management in tropical agroecosystems: application of an organic resource database

Organic resources play a critical role in both short-term nutrient availabi lity and longer-term maintenance of soil organic matter in most smaller hol der farming systems in the tropics. Despite this importance, there is littl e predictive understanding for the management of organic inputs in tropical agroecosystems. In this paper, an organic resource database (ORD) is intro duced that contains information on organic resource quality parameters incl uding macronutrient, lignin and polyphenol contents of fresh leaves, litter , stems and/or roots from almost 300 species found in tropical agroecosyste ms, Data on the soil and climate from where the material was collected are also included, as are decomposition and nutrient release rates of many of t he organic inputs. Examples of uses of ORD are provided in the paper: (1) n utrient contents (including median values and ranges) and other resource qu ality parameters of farmyard manure and crop residues are compared to that of alternative nutrient sources such as different plant parts and plant typ es; (2) nutrient stocks found in farm boundary hedges are estimated and eva luated as a source of nutrients for soil fertility management; (3) hypothes es regarding the indices and critical values of N, lignin, and polyphenol c ontents for predicting N release rates are tested; (4) organic materials fo r soil fertility management experiments are selected. This database, when c oupled with models and decision support tools, will help advance organic ma tter management for soil fertility improvement from an empirical to a predi ctive practice. (C) 2001 Elsevier Science B.V. All rights reserved.