The chemical characteristics of peat soil can be improved with soil amendments such as biochar derived from separate effects of OPEFB biochar and N fertiliser, along with their interaction, on the dynamics (loss, content, uptake) of nutrients in peat soil as well as on the growth of oil palm seedlings. A glasshouse experiment was carried out in North Sumatra (Indonesia) from December 2020 to February 2021 using a Complete Randomised Factorial design. The first factor was the OPEFB biochar dosages (0, 5, 10, 15 t ha(-1)) and the second factor was the dosage of N fertiliser (30, 45, 60 kg ha(-1)), with three replicates. The data were analysed using ANOVA and continued with Duncan at P < 0.05. The results showed that biochar doses of 10 and 15 t ha(-1) effectively reduced the losses of N and magnesium (Mg) by 15.7 and 7.56 %, respectively. These reductions were accompanied by increases in soil pH (by 5.12 %) and exchangeable potassium (by 48.3 %). The levels of the plant nutrients phosphorus (P), copper (Cu), potassium (K), calcium (Ca) and boron (B) in the oil palm seedlings were 17.8, 27.0, 5.88, 7.89 and 0.18 %, respectively. Furthermore, N fertiliser doses of 30-45 kg ha(-1) increased pH, total N and nutrient (N, B) content as well as the uptake of N, P, K, Mg, Ca, B and Cu. The interaction of 10-15 t ha(-1) biochar with 30-45 kg ha(-1) nitrogen fertiliser inhibited leaching of N but increased exchangeable-K and nutrient (N, P, K, Mg, Ca, B, Cu) contents. Based on our results, only N doses of 30-45 kg ha(-1) were effective in increasing the number of leaves, stem diameter and biomass of oil palm seedlings, while the effects of biochar and the interaction were insignificant. The findings of this study are relevant for oil palm plantations in peatland areas.
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