Gliricidia Sepium as a Source of Green Manure for Improving the Productivity of Tropical Smallholder Farming Systems

Abstract

Adopting agro forestry systems is a possible remedy for improving tropical smallholder farming systems located on degraded lands. Gliricidia sepium, which has the possibility to enhance soil fertility as well as to provide nutrients to crops over time, can be introduced in to these systems. Many studies have examined the impact of Gliricidia sepium on crop productivity under alley cropping systems. However, due to lack of studies on the use of green manures on enhancing the sustainability of tropical smallholder farming systems, a field study was carried out to determine the benefits of adding Gliricidia sepium green leaf manure to home gardens and adjacent cultivated fields located on sloping, moderate and flat terrains in the Meegahakiula region of Sri Lanka. Thirty households including home gardens and their adjacent cultivated fields were selected along the terrain. Field experiments were conducted using three treatments including NPK+Gliricidia, Gliricidia only and the control over the 2007/8 Maha and 2008 Yala seasons using maize and mung bean as the test crops, respectively. Soil sampling was done up to a depth of 60 cm considering the rooting depths of the selected crops to analyze soil quality and plant samples at crop maturity. Inclusion of green manure improved the soil properties significantly in home gardens in all categories irrespective of the slope. Yield increments were greatest in the eroded steep category due to Gliricidia green leaf manure while the beneficial impact was greater in maize than in mung bean. The incorporation of Gliricidia sepium as a source of green manure for sustaining crop yields in major and minor seasons in degraded lands in the tropics was clearly evident from this study.