Integrated oil palm nutrient management and its implication on environment quality

The high productivity of oil palm despite being mainly grown on weathered, degraded soils in the tropics may be largely attributed to the implementation of integrated nutrient management (INM). INM for oil palm was initially developed in the late 1960s to 1970s for estimating the major components of nutrient demand and supply in the agro-ecosystem, and any shortfall between them is met by chemical fertilizers. While this INM system can ensure high oil palm productivity, the environmental quality of the agro-ecosystem cannot be adequately assured particularly in relation to the principles and criteria of the Roundtable on Sustainable Palm Oil (RSPO). This paper discusses the various non-traditional sources of plant nutrients and their impact on the palms and the environment; many of them have been gradually incorporated into the above INM since the 1980s. Results showed that the right combination of legumes could increase the fresh fruit bunch (FFB) yields by 3.7 t/ha over 3 years and reduce P requirement by half through nutrient return from leaf litters. Preliminary studies in the oil palm nursery also clearly illustrated the effects of endo- and ectomycorrhiza, beneficial microbes, organic fertilizers, soil amendments and controlled release fertilizers with or without fertilizer supplements in enhancing seedling growth and nutrient use efficiency in highly weathered soils. Field studies demonstrated that leaching losses of N and K and groundwater contamination can be reduced substantially by matching the external nutrient inputs with plant nutrient uptake rate and rainfall distribution. There was also negligible to low impact of chemical fertilizer inputs on greenhouse gas emissions even in deep tropical peat soils. A keystone of the current INM is the reduction of pollution from plant nutrients which will ultimately lead to better nutrient use efficiency and a more holistic or effective INM for the oil palm agro-ecosystem.