Assessing potential climate smartness of agronomic practices in oil palm plantations

Oil palm (OP) plantations show potential for climate mitigation and adaptation, particularly in non-deforested and non-peatland areas, where carbon sinks are plausible. Agronomic practices like reduced nitrogen fertiliser combined with mechanical weeding or empty fruit bunch (EFB) application maintain yields while reduce N₂O emissions. Optimal EFB application rate and irrigation enhance soil organic carbon (SOC) and sustained photosynthesis respectively, lead to improved yields. However, most studies focus on the impact of these practices on yield, neglecting mitigation and adaptation performance under climate change.

Accordingly, this study applies the climate-smart agriculture (CSA) framework to evaluate agronomic practices in OP plantations  in North Sumatra, Indonesia. The Agricultural Production Systems sIMulator (APSIM) was used to assess seven scenarios of agronomic practices under changing climate conditions (UKESM1 and MP1 models with SSP 370 and SSP 585 pathways). Scenarios comprised: (1) business-as-usual (BAU), (2) reduced N fertiliser + 30 t ha⁻¹ yr-1 EFB, (3) reduced N fertiliser + 60 t ha⁻¹ yr-1 EFB, (4) irrigation at 10 mm deficit, (5) irrigation at 30 mm deficit, (6) irrigation at 30 mm deficit + 30 t ha⁻¹ yr-1 EFB, and (7) reduced N fertiliser + irrigation at 30 mm deficit + 30 t ha⁻¹ yr-1 EFB. Climate smartness was measured using carbon balance and two indices from the literature, based on yield, water use, greenhouse gas (GHG) emissions, and SOC stock changes.   

Results showed that irrigation is more effective than EFB application in increasing climate smartness. Irrigation scenarios resulted in increased yield, greater carbon sinks, higher water productivity, and lower GHG intensity by preventing stomatal closure during water deficits without causing an increase in emissions, and thus higher climate smartness scores. EFB application caused the smallest decline in SOC stock but led to the highest emissions, resulting in the lowest climate-smartness score. These findings highlight the effectiveness of irrigation in sustaining climate smartness, encompassing productivity and climate mitigation-adaptation in OP plantations, which has been underexplored in previous studies.