Mucuna bracteata: an assessment of its contributions to the fertility of acid sulfate soil / Mohd Fazri Mat Omar

Incorporation of leguminous cover crop (LCC) during early growth of oil palm plantation in Malaysia is a common practice. The main reason for this practice is to protect soil from erosion and to improve soil properties. This study focus on the assessment of the potential contribution of Mucuna bracteata to the fertility of acid sulfate soil. Furthermore, the effect of P fertilization and liming with CaCO3 on N accumulation through fixation by Mucuna bracteata was also assessed through pot experiment. The bacteria strain responsible for N fixation by Mucuna bracteata in acid sulfate soil was also screened and determined. For field study, soil samples for chemical analysis was drawn at the depth of 0 cm – 15 cm while for physical analysis at 0 cm – 5 cm and 15 cm – 20 cm. Soil samples were analysed for organic matter, total nitrogen, available P, cation exchange capacity, exchangeable Ca, Mg, K, and Na as well as soil bulk density and aggregate stability. Mucuna bracteata treatment showed significant increased in organic matter, total nitrogen, cation exchange capacity and available P averaged at 1.59%, 4.34%, 10.58 meq/100 g soil and 2.82 ppm respectively. Bulk density showed decrement of 0.25 g/cm3 while aggregate stability was increased by 9.94%. Determination of responsible bacteria strain which nodulate Mucuna bracteata was carried out by isolation using streak plate method while the identification by using polymerase chain reaction and genomic extraction method. Bacteria strain responsible for N fixation was Rhizobium tropici strain B28. Factorial Completely Randomized Design (CRD) was used in the study on P fertilization with CaCO3 on N accumulation through fixation by Mucuna bracteata. Parameters studied were soil pH, plant biomass, nodule number, soil available P, plant P and leaves N. Combination rate of CaCO3 and P fertilizer at 20g CaCO3 per pot and 7.5 g per pot recorded the best effect in term of soil pH, plant biomass, nodule number, soil available P, plant P and leaves N. Incorporation of Mucuna bracteata in oil palm plantation significantly improved soil properties which enhanced soil fertility. Effective rhizobium strain should be inoculated prior to Mucuna bracteata planting. P fertilization and liming with CaCO3 should be extensively applied on Mucuna bracteata in oil palm plantation