ABSTRACT

Nitrogen fertilizer application is crucial in maintaining soil fertility and crop productivity in oil palm (Elaeis guineensis Jacq.) plantations. However, the effects of N addition on soil’s chemical and biological properties, particularly tropical peat are still unclear. This study investigated the impact of N fertilizer addition on peat properties, greenhouse gas (GHG) fluxes, soil bacterial and fungal diversity in an oil palm plantation on tropical peat. A long-term field experiment (from 2012 to 2013 and 2016 to 2017) was conducted to compare the application of 124.3 kg N ha ⁻¹ y ⁻¹ of ammonium sulfate (the treatment) to no N application (the control). Baseline data were collected from a primary peat swamp. Overall, N fertilizer input slightly decreased soil pH, total carbon (C), total N, pyrophosphate solubility index (PSI) but increased nitrate (NO₃⁻), ammonium (NH₄⁺) concentration, methane (CH₄), and nitrous oxide (N₂O) fluxes. The result suggested a reduction in soil bacterial diversity but an increase in soil fungal diversity. Forest soil showed naturally low NO₃⁻ concentration but a NH₄⁺ concentration comparable to that in the oil palm plantation. These findings provide evidence of changes in soil chemical and biological properties from long-term ammonium sulfate application on tropical peat.

摘要

氮肥施用对于维持油棕 ( Elaeis guineensis Jacq.) 种植园的土壤肥力和作物生产力至关重要。然而，氮添加对土壤化学和生物特性的影响，尤其是热带泥炭的影响仍不清楚。本研究调查了氮肥添加对热带泥炭油棕种植园泥炭特性、温室气体 (GHG) 通量、土壤细菌和真菌多样性的影响。进行了长期田间试验（2012 年至 2013 年和 2016 年至 2017 年）以比较 124.3 kg N ha ^-1 y ^-1硫酸铵（处理）到不施氮（对照）。基线数据是从原始泥炭沼泽中收集的。总体而言，施氮肥略微降低了土壤 pH 值、总碳 (C)、总 N、焦磷酸盐溶解度指数 (PSI)，但增加了硝酸盐 (NO 3 - )、_铵⁽ NH ₄ ⁺ ) 浓度、甲烷 (CH ₄ ) 和亚硝酸盐氧化物 (N ₂ O) 通量。结果表明土壤细菌多样性减少，但土壤真菌多样性增加。森林土壤显示天然低 NO ₃ ^-浓度，但 NH ₄ ⁺浓度可与油棕种植园相媲美。这些发现提供了长期在热带泥炭上施用硫酸铵会导致土壤化学和生物学特性发生变化的证据。