Impact of Green Manure on Productivity Patterns of Homegardens and Fields in a Tropical Dry Climate

Extensive field farming and homegardening (representing an intensive resource management system) on different inclination positions were compared on the basis of soil quality and productivity of maize and Mung bean over two years, in Meegahakiula, Sri Lanka. Soil organic matter (SOM) content of homegardens was greater than in fields irrespective of the inclination and it was more pronounced in the flat category. After two years, SOM declined in both homegardens and fields, the depletion of SOM was greater in homegardens, due to a positive correlation between SOM depletion rate and crop yields. Green manures moderated SOM depletion. Mean maize yields in homegardens with recommended fertilizers (NPK) exceeded 5 Mg.ha and was significantly different from Fields in both Flat and Moderate categories. No yield difference was observed in homegardens and Fields in the Steep category. Although mineral fertilizers had an overriding effect over green manures, plots without fertilizers (ZERO and G) had higher yields in homegardens. Mungbean yield was similar in homegardens and Fields with recommended fertilizers (NPK) in Flat category, in both years. However, the difference became significant with increasing inclination. The influence of green manure was overridden by the influence of mineral fertilizers while no difference was observed between homegardens and Fields without mineral fertilizers (ZERO). The study illustrated that homegardens as an intensive resource management system is more fertile and productive than the extensive field farming and more effective in terms of long term sustainability.