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The accuracy of fertiliser recommendations can be improved by knowledge of use efficiency of applied nutrients. The aim of this work was to determine the efficiency with which mature oil palm (Elaeis guineensis Jacq.) recovers and uses fertiliser K and Mg under different environmental conditions in Sumatra, Indonesia. The work was carried out in seven factorial fertiliser trials (NPKMg) at sites with contrasting soils, slope and rainfall (1500–3500 mm annual average). We recorded the palms' fresh fruit bunch yield (weekly), vegetative growth and nutrient content (annually), and soil properties (once during the study) over three years. Nutrient content of the above-ground palm components was calculated by multiplying concentration by biomass. Palm responses to K and Mg application were analysed at non-limiting values of the other nutrients. Fresh fruit bunch yield was significantly increased by application of K in five of the seven sites (by 4.8–11.9 t ha−1) and by Mg in two of the seven sites (by 7.2–12.3 t ha−1). Application of these fertilisers also significantly increased growth and nutrient content in most situations. Nutrient use efficiency declined with increasing yield and nutrient uptake. In the five sites with most positive yield responses to K, agronomic efficiency of K and Mg differed between sites due to differences in recovery efficiency. Recovery efficiency was correlated positively to soil K, Mg and silt content and rainfall, and negatively to slope and soil moisture deficit. In contrast, physiological efficiency of K and Mg use was similar across sites, despite differences in palm age and planting density. It thus appeared that physiological efficiency was determined by genotype and that variation in agronomic efficiency was mostly a result of differences in recovery efficiency. [ABSTRACT FROM AUTHOR]

Identifying optimal fertilizer management to ensure high nutrient use efficiency is important to reduce negative environmental impacts in oil palm (Elaeis guineensis) cultivation. A 4-year fertilizer trial was established in an oil palm plantation, located at a sandy area with occasional monthly water deficit in Central Kalimantan. We examined the responses of oil palm yield and nutrient use efficiency to fertilizer application frequency (standard frequency of 1-2 times yr−1 versus 4 times yr−1) and rate (standard rate of 136, 12, and 200 kg ha−1 yr−1 of N, P and K, respectively versus 80% of standard rate). There were no treatment effects on annual yield in fresh fruit bunch, bunch number, or individual bunch weight. Increasing fertilizer frequency did not increase nutrient use efficiency at the last 2 years of the trial. In contrast, reducing fertilizer rate resulted in higher nutrient use efficiency in K, compared to the standard treatment and increasing fertilizer frequency. Average concentrations of N, P, K, Mg, Ca, and Cl in leaflet under all treatments were above critical levels both in the beginning and at the end of the trial. Monthly yield in fresh fruit bunch correlated positively with soil water balance with correlation coefficients of 0.24-0.29, during the developmental period of inflorescence sex differentiation at 28-30 months before fruit maturity. Our study provides useful information for fertilizer management optimization in sandy areas with occasional water deficit, corresponding to most of the new expansion areas of oil palm in Southeast Asia. [ABSTRACT FROM AUTHOR]

In Indonesia more than 40% of the area under oil palm is owned by smallholders. The productivity in smallholder plantations is usually less than in large plantations, and limited fertiliser applications may be one of the key reasons. We investigated the use of fertilisers by > 300 smallholder farmers in Sumatra and Kalimantan, some of whom were involved in training programmes aimed at yield improvement. In our sample, the total applications of N were largest (166 kg ha−1 year−1), followed by K (122 kg) and P (56 kg). The applications of K were insufficient to compensate for the off-take with a production of 20 tonne fruit bunches ha−1 year−1, while N applications were excessive. On average, farmers applied 1130 kg fertiliser ha−1 year−1, and relied strongly on subsidised fertilisers, especially NPK Ponska (66%) and urea (39%). The average costs for fertiliser application were USD 225 ha−1 year−1. Trained farmers applied significantly more P in one research area, but for the other nutrients and research areas, there was no significant difference between trained and untrained farmers. Plantation size and nutrient application were weakly correlated in some areas, but not in the sample as a whole. Previously reported nutrient application rates were mostly less than our findings indicated, suggesting that actual nutrient limitations may be more severe. To overcome nutrient limitations and enhance nutrient use efficiency, we recommend that fertilisers are used in the correct balance; a ground cover vegetation is maintained to protect against erosion; and the application of empty fruit bunches is encouraged. [ABSTRACT FROM AUTHOR]

Potassium is the main nutrient in oil palm nutrition. On oil palm estates, potassium fertilization is usually adjusted based on leaflet K content. However, in the Magdalena river valley in Colombia where the soils are deficient in Cl, KCl has always caused a drop in leaflet K content, sometimes to deficiency levels, yet yields remain high. To elucidate this paradox, we conducted a multi-annual trial on 11-year-old oil palms by comparing unfertilized plots and plots receiving KCl or NaCl. We analysed the physico-chemical characteristics of the soils and the K, Ca, Mg, Na, and Cl contents of different organs: leaflets, rachises, petioles, stems, roots, and fresh fruit bunches. Our results showed that Cl stimulated the uptake of K, Ca, and Mg cations in aerial parts and that K was primarily stored in the stem (72% of the K in aerial vegetative organs). Our results also showed that the soils were rich in K easily accessible to the crop, a fact that conventional extraction of exchangeable cations did not reveal, and that the richness was probably of volcanic origin. Lastly, analysis of rachis K content was seen to be a good potential indicator of K taken up by the plant, and could thus replace leaflets for monitoring potassium fertilization in oil palm plantations. [ABSTRACT FROM AUTHOR]