Effect of Cover Crops on Weed Suppression in Oil Palm Plantation

Weeds are a major problem in oil palm plantation and use of herbicides is a common way for weed control. Cover crops have the potential to control weeds in oil palm areas. Hence field experiments were designed over two years in an oil-palm plantation in Malaysia to compare the effect of cover crops on common local weed species. Six treatments include four ground covers viz. Axonopus compressus, Calopogonium caeruleum + Centrosema pubescens, Mucuna bracteata and Pueraria javanica + C. pubescens, and glufosinate-ammonium herbicide (weeded), and natural vegetation (un-weeded) were evaluated. A. compressus, M. bracteata and other legume cover crops achieved 100% coverage at 3, 6 and 9 months after planting, respectively. Cover crops and un-weeded treatments produced comparable vegetation biomass. A. compressus and M. bracteata produced higher total biomass (800 g m(-2)) compared to the both mix of the conventional legume cover crops (600 g m(-2)). The weed densities, in the un-weeded plots were 255, 544, 419, 445 and 502 plants m(-2) at 9, 12, 15, 18 and 24 months after planting, with the corresponding biomasses of 254, 804, 395, 630 and 734 g m(-2), respectively. The decline in percentage weed dry weight and weed density due to the cover crop treatments in comparison to the un-weeded treatment ranged between 97.3 - 99.9% and 94.77 - 99.73%, respectively. High levels of phenolic compounds were observed from the P. javanica + C. pubescens treatment. The study suggests that cover crop management systems have potential to be include in sustainable oil palm plantation for reduce use of herbicides. The results also suggest that A. compressus could be considered as a suitable candidate as a cover crop under oil palm. (C) 2015 Friends Science Publishers