Coconut based homegardens: mechanisms of complementarity in growth resources sharing among homegarden trees in the humid tropics

Abstract

Complementarity among tree species in sharing the growth resources is a key to the sustainability in crop productivity. However, information on how the species separate their niches above- as well as below the ground and develop complementarity in sharing the growth resources is poorly known for the homegardens of humid tropics. This study reports aboveground growth resource (sunlight) sharing, and pattern of fine root biomass distribution, and uptake of N, P and K by the coconut tree (main crop) and its intercrops (clove and nutmeg trees) in a coconut-clove and a coconut-nutmeg plantation in the South Andaman Islands of India. The main crop and its intercrops have the same geometry in the plantation as they have in homegardens of the islands. The study included three tree species (coconut, clove and nutmeg), and five distances (0.75, 1.50, 2.65, 3.80 and 4.55 m) from the coconut towards its intercrops. The coconut intercepted 30-32 % sunlight above the canopy of its intercrops. The intercrops, in turn, restricted their root distribution up to 2.65 m from their trunk. The coconut, however, extended its roots quite close to its intercrops. In addition to its own niche, the coconut mined nutrients from underneath of its intercrops, but the intercrops utilized the nutrients only from their niches. These observations suggest that trees in homegardens separate their niches horizontally below the ground and, thereby, develop complementarity in the growth resource sharing. Above the ground, the main crop, however, intercepts light and imposes partial shade on its shade-loving intercrops. This information has bearing for managing above- and belowground growth resource sharing in agroforestry systems.