Soil physical conditions and root growth in coconut plantations interplanted with nitrogen fixing trees in Sri Lanka
1997
Vidhana Arachchi, L. P. | De S Liyanage, M.
The study was carried out to investigate the possibility of improving degraded soil conditions of Andigama series by intercropping coconut (Cocos nucifera L.) with Calliandra calothyrsus, Leucaena leucocephala, Acacia auriculiformis and Gliricidia sepium. Bulk density was significantly low in NFT interplanted plots followed by improved aeration in AB and B horizons of the soil profile. Total and readily available water fraction was higher in AB and B horizons of calliandra, acacia and gliricidia interplanted plots over control plots due to the increase of organic matter content and root growth. Root growth and proliferation of calliandra in A horizon were predominantly higher than that of leucaena, acacia and gliricidia species. In contrast, gliricidia roots penetrated into B horizon more densely than roots of other species. Better root growth of coconut in A horizon was observed in acacia and calliandra plots than other plots. The total coconut root biomass in AB and B horizons was higher in gliricidia and acacia plots than other species, which accounted for 91% and 0.3% in AB horizon and 21% and 23% in B horizon for gliricidia and acacia, respectively compared to the control. Total root biomass of coconut in calliandra plots was reduced by 5%, and 45% in AB and B horizons respectively. Results indicated that soil physical conditions of Andigama series (gravelly soil) could be significantly improved by interplanting acacia and gliricidia, as indicated by enhanced coconut root growth and proliferation.
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