SHADE TOLERANCE POTENTIAL OF SOME TROPICAL FORAGES FOR INTEGRATION WITH PLANTATIONS 2. LEGUMES

C.C. WONG. M.A. MOHD. SHARUDIN and H. RAHIM

Abstract

In a comparative evaluation of 14 tropical legumes under pot culture in a greenhouse, Calopogonium caeruleum was the best in overall shade tolerance followed by Pueraria phaseoloides, Alysicarpus vaginalis and Desmodiumo valifulium. The Stylosanthes species and D. triflorum and D. heterophyllum were ranked the lowest. The best dry matter(DM) yielders across all shade levels were P. phaseoloides, C. mucunoides and C. caeruleaium. A reduction in the photosynthetic quantum flux (PHAR) by 44%,66% and 82% of that in the unshaded control resulted in a corresponding overall mean DM yield reduction of plant tops by 30%, 55% and 71% of that of the unshaded control. Calopogonium mucunoides, C. caeruleum and D. ovalifulium gave quadratic response in DM yield to light levels with an optimum at 57% of PHAR in full sunlight. In the field trial, Stylosanthes guianensis cv. Endeavour gave the highest annual DM yield at all shade levels followed by D. ovalifulium, C. caeruleum and P. phaseoloides. Centrosema pubescens had the lowest DM production. A reduction in PHAR by 40%,66% and 82% of that in full sunlight resulted in a corresponding decline in overall mean DM yield by 36%,43% and 60% of that in the unshaded control. Generally, the five forage legumes were not persistent in maintaining high DM productivity over harvests. Dry matter percentage of plant tops, specific leaf area and shoot/root ratio increased with shading intensity while root percentage and nodule number declined. Leaf and stem percentages increased marginally with shade intensity. leaf area increased non-significantly under low shade but declined in heavy shade. Nitrogen content differed among species and generally increased among shade regimes except for the most intense shade.

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