Yield responses of oil palm to NPK fertiliser application on an alluvial soil in Indonesia.

摘要

A 33 factorial fertilizer trial established on D x P oil palms planted on riverine alluvium in North Sumatera, Sumatra, Indonesia, during 1992-98, recorded significant yield responses to fertilizer application. Of the three major nutrients evaluated, the highest yield increase resulted in phosphate (P) fertilizer. Significant yield responses were recorded for P application in six out of the seven years of harvesting. On average, P application increased fresh fruit bunch (ffb) yields by 45% or 7.4 t/ha/year. Yield response to nitrogen (N) was intermediate between that of P and potassium (K). Significant yield responses were recorded for N fertilizer in five out of seven years of harvesting and N application increased yields by 10% or 2.0 t/ha/year.A positive N x P interaction was also observed. Maximum yield response to N only occurred in the presence of P fertilizer and vice-versa. Yield response to K was low, with significant responses recorded in only two out of seven years of harvesting. On average, K application increased ffb yield by only 4% or 0.8 t/ha/year. However, there were strong indications that K was required for the maximum expression of the yield response to both N and P, as the highest yields were only attained with the inclusion of K fertilizer. Economic analysis clearly indicated the profitability of applying fertilizers even at low crude palm oil and high fertilizer prices. Maximum profitability was achieved with the treatment receiving the first level of N and Mg and secondlevel of P and K (N1P2K2Mg1), which was also the highest yielding.