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Inadequate availability of nutrients and leaching losses due to water table fluctuations is a serious concern in oil palm cultivation on tropical peat land. The objectives of the study were to determine peat subsidence and leaching losses of N, P, K, Mg, Ca, Cu, and Zn from tropical peat soil under cultivation of oil palm seedlings at different water table depths. The study was conducted using cylindrical lysimeters with five water table depths namely, 25, 40, 55, 70, and 85 cm from the soil surface. The experimental layout was a Randomised Completely Block design. Leachate from each lysimeter was collected after a rainfall event to determine the leaching loss of nutrients. The highest water table depth (25 cm) from the soil surface showed the highest nutrient leaching losses, and the lowest water table depth (85 cm), showed the highest subsidence and lowest nutrients leaching losses. Plant growth was highest under the 55 cm water table depth, and the lowest under the highest and lowest water table depths of 25 and 85 cm. The 55 cm water table depth was the best for oil palm growth because the active root zone of oil palm is within the 60 cm soil depth.

Inadequate availability of nutrients and leaching losses due to water table fluctuations is a serious concern in oil palm cultivation on tropical peat land. The objectives of the study were to determine peat subsidence and leaching losses of N, P, K, Mg, Ca, Cu, and Zn from tropical peat soil under cultivation of oil palm seedlings at different water table depths. The study was conducted using cylindrical lysimeters with five water table depths namely, 25, 40, 55, 70, and 85 cm from the soil surface. The experimental layout was a Randomised Completely Block design. Leachate from each lysimeter was collected after a rainfall event to determine the leaching loss of nutrients. The highest water table depth (25 cm) from the soil surface showed the highest nutrient leaching losses, and the lowest water table depth (85 cm), showed the highest subsidence and lowest nutrients leaching losses. Plant growth was highest under the 55 cm water table depth, and the lowest under the highest and lowest water table depths of 25 and 85 cm. The 55 cm water table depth was the best for oil palm growth because the active root zone of oil palm is within the 60 cm soil depth.

This study was conducted to understand the effects of fertiliser type (straights, compounds and controlled-release fertilisers) on N, P, K and Mg losses by surface runoff. The study was conducted in a mature oil palm field using three 20 m by 6 m erosion plots containing two palms per plot with the soil type being Typic Kandiudults and slopes ranging from 5.5° to 7.5°. Nutrient losses were measured in the eroded sediment and runoff water for every rainfall event over a period of 24 months. Nutrient losses were higher in the runoff water than in the eroded sediments. Broadcast application of controlled-release fertilisers and its slow dissolving nature made it prone to washing down the slope. Hence, higher nutrient losses were observed in the controlled-release fertilisers compared to other treatments. Compound fertilisers showed lower total losses for N (4.96%), K (3.95%) and Mg (0.65%) compared to straight fertilisers. Lower P losses were observed in the straights compared to the compound fertilisers due to higher percentage of soluble P in the compound fertilisers. Controlled- release fertilisers recorded high nutrient losses in the sediments caused by the washout Except for nitrogen, controlled-release fertilisers recorded higher losses for P (56.56%), K (19.83%) and Mg (10.36%) compared to straight fertilisers. Nitrogen losses were 18.15% lower in the controlled-release fertilisers compared to straights. Compound fertilisers showed lowest losses for N and K compared to straight fertilisers. Based on the data, it is postulated that compound fertilisers can lead to better nutrient uptake compared to straight fertilisers. However, this hypothesis needs to be tested through field experiments measuring nutrient uptake and its effect on oil palm productivity.

This study was conducted to understand the effects of fertiliser type (straights, compounds and controlled-release fertilisers) on N, P, K and Mg losses by surface runoff. The study was conducted in a mature oil palm field using three 20 m by 6 m erosion plots containing two palms per plot with the soil type being Typic Kandiudults and slopes ranging from 5.5° to 7.5°. Nutrient losses were measured in the eroded sediment and runoff water for every rainfall event over a period of 24 months. Nutrient losses were higher in the runoff water than in the eroded sediments. Broadcast application of controlled-release fertilisers and its slow dissolving nature made it prone to washing down the slope. Hence, higher nutrient losses were observed in the controlled-release fertilisers compared to other treatments. Compound fertilisers showed lower total losses for N (4.96%), K (3.95%) and Mg (0.65%) compared to straight fertilisers. Lower P losses were observed in the straights compared to the compound fertilisers due to higher percentage of soluble P in the compound fertilisers. Controlled- release fertilisers recorded high nutrient losses in the sediments caused by the washout Except for nitrogen, controlled-release fertilisers recorded higher losses for P (56.56%), K (19.83%) and Mg (10.36%) compared to straight fertilisers. Nitrogen losses were 18.15% lower in the controlled-release fertilisers compared to straights. Compound fertilisers showed lowest losses for N and K compared to straight fertilisers. Based on the data, it is postulated that compound fertilisers can lead to better nutrient uptake compared to straight fertilisers. However, this hypothesis needs to be tested through field experiments measuring nutrient uptake and its effect on oil palm productivity.