Growth and Control of Mucuna bracteata DC. ex Kurz

Muhammad Shafi, Ibrahim (2019) Growth and Control of Mucuna bracteata DC. ex Kurz. Masters thesis, Universiti Malaysia Sarawak.

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Abstract

As the most high yielding oil crop in the world, oil palm plantation is highly exposed to the major yield limiting threats caused by weed infestation and soil degradation. Establishment of leguminous cover crops (LCC) offers wide range of advantages besides suppressing weeds and improving soil fertility by fixing nitrogen (N). Mucuna bracteata DC. ex Kurz has shown superior performance as a LCC in oil palm plantations. However, the maintenance of this LCC is crucially challenging as the vigorous vines spread rapidly via branching from the nodes and compete with the crop plant for light source. The present study is mainly focused on the effect of shading and root conditioning on growth and development of M. bracteata, as well as to find the response of M. bracteata to four selected herbicides. Plants grown under 0% shade resulted higher values in plant height, number of leaves, total dry weight, total leaf area, specific leaf area (SLA), leaf area ratio (LAR), dry matter production (DMP), and leaf area duration (LAD) followed by 50% and 75% shades respectively. Shading decreased the biomass partitioning into roots. Higher net assimilation rate (NAR) was recorded in shaded plants. Root conditioning were done by planting with full polybag (T1), base cutting (T2), and polybag removal before planting (T3). T3 plants exhibit growth of longer vines, more leaves and branches, with higher biomass followed by T2 and T1 plants respectively. T2 plants resulted increased in growth rate on third month after transplanting by approximately same DMP produced by T1 which was higher than T3 plants. Differences in herbicides active ingredient and application rates significantly affected the control of M. bracteata via palm base circle spraying. The efficacy of four selected herbicides with recommended rates in descending order was: 2,4-D (0.4-0.6L ha-1) > metsulfuron methyl (120-160g ha-1) > glyphosate isopropylamine (2.5L ha-1) > MSMA+diuron (2.5-3.0L ha-1). The lowest effective control was shown by contact herbicide that did not completely desiccate the underneath vines which resulted lower control percentage, control duration, and higher regeneration rate. The findings on shading and root conditioning effect may suggest options for plantation management on the optimum time, condition, and planting technique for M. bracteata establishment, while suitable herbicide active ingredient with optimum application rate is crucial for cost effective control. Keywords: Mucuna bracteata DC. ex Kurz, shading, root conditioning, herbicide response, growth analysis, biomass partitioning

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