Abstract. Nutrient leaching in intensively managed oil palm plantations can diminish
soil fertility and water quality. There is a need to reduce this
environmental footprint without sacrificing yield. In a large-scale oil palm
plantation in Acrisol soil, we quantified nutrient leaching using a full
factorial experiment with two fertilization rates (260 kg N, 50 kg P, and 220 kg K ha−1 yr−1 as conventional practice and 136 kg N, 17 kg P, and 187 kg K ha−1 yr−1, equal to harvest export, as reduced management) and two
weeding methods (conventional herbicide application and mechanical weeding
as reduced management) replicated in four blocks. Over the course of 1 year, we collected monthly soil pore water at 1.5 m depth in three distinct
management zones: palm circle, inter-row, and frond-stacked area. Nutrient
leaching in the palm circle was low due to low solute concentrations and
small drainage fluxes, probably resulting from large plant uptake. In
contrast, nitrate and aluminum leaching losses were high in the inter-row
due to the high concentrations and large drainage fluxes, possibly resulting
from low plant uptake and low pH. In the frond-stacked area, base cation
leaching was high, presumably from frond litter decomposition, but N
leaching was low. Mechanical weeding reduced leaching losses of base cations compared to the conventional herbicide weeding probably because
herbicides decreased ground vegetation and thus reduced soil nutrient
retention. Reduced fertilization rates diminished the nitrate leaching losses. Leaching of total nitrogen in the mechanical weeding with reduced
fertilization treatment (32±6 kg N ha−1 yr−1) was less
than half of the conventional management (74±20 kg N ha−1 yr−1), whereas yields were not affected by these treatments. Our
findings suggest that mechanical weeding and reduced fertilization should be
included in the program by the Indonesian Ministry of Agriculture for
precision farming (e.g., variable rates with plantation age), particularly
for large-scale oil palm plantations. We further suggest including
mechanical weeding and reduced fertilization in science-based policy
recommendations, such as those endorsed by the Roundtable for Sustainable
Palm Oil association.