Comparison of integrated nutrient management in oil palm and rice in Southeast Asia
2001
Fairhurst, T. ((Potash & Phosphate Institute of Canada, 126 Watten Estate Road, Singapore 287599 (Singapore). East & Southeast Asia Programs))
Oil palm and rice account for a large proportion of the fertilizer nutrients consumed in Southeast Asia, yet they contrast markedly in the potential for integrated nutrient management. Both crops require inputs of potassium (K) and phosphorus (P) fertilizer nutrients all of which are presently imported into the region. Recycling and efficient fertilizer use to maximize the return on foreign exchange used, are therefore important strategic goals for Southeast Asian countries. This paper compares and contrasts present nutrient management practices and the potential for integrating organic and inorganic sources in rice and oil palm. The vegetable oil products of oil palm contain very small amounts of minaeral nutrients yet the crop requires large amounts of fertilizer inputs. This paradox is explained by the difficulties involved in recycling the nutrients contained in crop residues (bunch residues and effluents). Larger amounts of nitrogen (N), P and K are exported in rice but the removal of K is greatly increased when rice straw is removed after harvest and sold for off-farm use. In rice, integrated nutrient management, involving the recycling of animal manures and crop residues is practiced assiduously in countries where the opportunity cost of labor is low (e.g. Vietnam). Where the opportunity cost of labor is higher as in more industrialized countries (e.g. Malaysia), nutrient recycling is less economic for farmers and mineral fertilizers become the major nutrient source. In both crops there is potentialto capture atmospheric N2 by integrating legume plants in the cropping system. In oil palm, legume cover plants (e.g. Pueraria phaseloides) can provide 150 kg N per ha per year but only during the three years from field planting to crop maturity. In rice cropping systems, Azolla and Sesbania rostrata are used to provide N to the following rice crop but their use is feasible only where the opportunity cost of labor is low and the efficient capture of fixed N is impaired by the mobility of N in soil. Farmers are also reluctant to incorporate legumes in rice cropping systems where their use results in a decrease in the number of crops grown each year. The potential for integrated nutrient management in rice and oil palm is thus related to each crop's agronomic characteristics and the level of economic development in each country.
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