Yield Responses of Young Mature Oil Palms to NPK Fertiliser Application on Deep Peat in North Sumatera Province, Indonesia

摘要

In Indonesia, where there has been extensive expansion of oil palms onto peat soils, published research on its nutritional requirements is still very limited. In view of this, a series of fertiliser trials were established to determine both its macroand micro nutrient requirements and early findings from two trials are reported here. Although the nitrogen (N) content of peat is high, due to a slow mineralisation rate, its initial availability to newly planted oil palms maybe very limited. This was reflected by a significant and linear response to N fertiliser in trial no.l, optimum application rates being 1.00-1.50 kg urea per palm per year. Positive responses to N manuring were recorded throughout the five-year period and there was no decline in Nrequirement with time. Unlike nitrogen, no significant responses to phosphorus (P) fertiliser were recorded. Low inputs of 0.50 kg RP per palm per year being sufficient to maintain optimum leafP status. Potassium (K) requirements varied with the stage of mineralisation of the peat and oil palm fresh fruit bunch (ffb) yield. On younger, fibric peat with ffb yields averaging below 23 tonnes per hectare (trial no.l), inputs of 3.00 kg MOP per palm per year were just as effective as 4.50-6.00 kg MOP per palm per year. However, on older peat where ffb yields exceeded 30 tonnes per hectare (trial no.2), K demand by the palms was much higher with optimum MOP rates being 6.00 kg per palm per year. A cost benefit analysis carried out for both trials clearly indicated the profitability of applying fertilisers even at low ffb and high fertiliser prices.