Value of composted organic wastes as an alternative to synthetic fertilizers for soil quality improvement and increased yield
One of the major problems with agricultural soils in the tropical region of the western Pacific islands is their low organic matter content, which results from rapid decomposition due to the hot and humid environment. Composted organic material is frequently applied on agricultural fields as an amendment to provide nutrients and also to increase the organic matter content and to improve the physical and chemical properties of soils. Our goal is to develop management strategies that can use available organic wastes on the farm for improving soil quality for better crop production while conserving resources and preserving environmental quality. The project described here is designed to improve soil fertility by addition of composted organic wastes and to assess the contribution of nitrogen and other essential nutrients to long-term soil fertility and crop productivity in the absence of synthetic fertilizers. In our pilot project, compost was produced from wood chips derived from grounded typhoon debris and animal manure, fish feed, and other organic wastes available at or in proximity of the farms. Mature compost was then applied to experimental plots of the eroded Cobbly soils of southern Guam at a rate of 0, 74, 148, or 296 metric tons per hectare. Maize planted on the plots showed great increases in both quality and yield, and the soil quality improved with each successive application of compost.