Chemical Forms and Distribution of Soil Micronutrients at An 18-year-old Oil Palm Field in Central Pahang, Malaysia

抄録

Chemical forms and distribution of manganese (Mn), iron (Fe), copper (Cu), and zinc (Zn) in soils under oil palm cultivation were investigated at an 18-year-old oil palm field in central Pahang, Malaysia. Soils were sampled at three micro sites under different agronomic management (weeded circle, frond heap and harvest path). In the surface soils, total Mn at the frond heap was significantly higher than at the weeded circle and the harvest path, and total Zn was highest at the weeded circle. Amounts of diethylene triamine pentaacetic acid (DTPA) extractable Mn, Fe, Cu and Zn at the frond heap were higher than at the harvest path. Results of sequential fractionation indicated that Mn in the acid soluble, Mn oxide-occluded, and organically bound fractions were higher at the frond heap than at the harvest path. On the other hand, the amount of Mn in the heaped fronds was highest among the examined micronutrients. These results suggest that release of Mn during decomposition of heaped fronds increased the amounts of Mn in the above mentioned fractions, which in turn contributed to the increment of total and available Mn in the surface soil at the frond heap. It is also supposed that frond heaping practice affects the distribution of Fe, Cu, and Zn. This study shows that, as well as soil macronutrients, the dynamics of soil micronutrients in oil palm fields are influenced through the practice of frond heaping.