Potensi evapotranspirasi dan hasil serta kehilangan larutlesap tanaman sawit.
1991
Foong S.F.
Peninsular Malaysia has a humid tropical climate with rainfall of 1800 to 3000 mm per annum. However the distribution of the rainfall is not even, with distinct droughts in February-March and July-August and a wet monsoonal period from November-December. The evapotranspiration will be restricted during the drought while heavy losses of fertilizer during the monsson will result in lower crop production. A lysimeter was set up to provide information on the potential evapotranspiration and the extent of leaching losses for establishing guidelines for irrigation and fertilizer application. For immature palm, the potential evapotranspiration (PET) is about 4-5 - 5.0 mm/day and for mature palm, the PET is about 5.5 mm/day. However, during the drought, the PET may increase to 6.5-7.5 mm/day depending on the severity of the drought. If economically feasible, irrigation requirement should be based on the above PET values so as not to restrict the growth and production. At immature stage of oil palm, the potential yield could reach 40-45 t/ha and 50-54 t/ha at mature stage. However sustainable yield at mature stage should be 40-45 t/ha at peak production age and then gradually decline with advancing palm age. Such potential yield should be achievable with proper irrigation, fertilizer application and agronomic practice. Leaching losses from the lysimeter (clay loam soil) is about two to five percent of the applied fertilizer. However, there is disproportionate losses amongst the major nutrients. Magnesium loss could be as high as 10-20 percent and occasionally even exceeding 30 percent. Nitrogen and Potassium losses are about similar at two to six percent while Phosphorus loss is the least at one to three percent.
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