Application of ammonium sulfate affects greenhouse gases and microbial diversity of an oil palm plantation on tropical peat

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.