<em>LEUCAENA</em> AS A MULTIPURPOSE TREE FOR COCONUT PLANTATIONS IN SRI LANKA

Abstract

A series of experiments on Leucaena leucocephala conducted at the Coconut Research Institute of Sri Lanka revealed its adaptability under coconut in different agro-climatic zones. The highest biomass yield (13.4 ( ha^-1 y^-1) was obtained in the Dry Zone on Entisols with a pH of 6.0 indicating its adaptability to non-acid soils in dry area. In another trial, application and incorporation of 30 kg palm^-1 fresh loppings of Leucaena as a green manure around the palm showed that nutrients released from its decomposition could provide the entire nitrogen and about 20% of phosphorus and potassium requirements of an adult palm. The beneficial effects of Leucaena on soil physico - chemical properties were demonstrated by a substantial improvement on Ultisols in terms of increased organic carbon content (45%) and water holding capacity (82%) and reduced bulk density (3%) over the control. The enhanced earthworm activity in Leucaena plots further indicated its significant role in soil improvement. Fresh Leucaena loppings placed in a quarter circle trench around low yielding palms on degraded Utisols resulted in 29% increase in nut production and 51% increase in copra yield compared with those in control plots. Leucaena (cv. K636) grown in the avenues between coconut rows and along the boundary fence in the Intermediate Zone proved to be a potential source of drought feed for cattle raised under coconut. During the dry season feeding up to 6 kg of fresh loppings of Leucaena mixed with (Gliricidia sepium) in 1:1 ratio to supplement the low quality roughage such as rice straw given at 10 kg^-1 head^-1 day^-1 resulted in live weight gains of cattle in the range of 306 to 680 g head^-1 day^-1. In another trial to estimate fuelwood value, Leucaena (cv. K8) grown under coconut in double rows produced the highest wood yield (5.17 t ha^-1 ) three years after planting. The coconut palms also benefited most from the double row system as indicated by 8-13% increase in nut
and 7-8% increase in copra over control plots without Leucaena. These results suggest that Leucaena could play a significant role in raising the productivity of coconut lands in Sri Lanka.