Assessment of direct nitrous oxide emissions and emission factors from sugarcane plantations using different rates of chemical fertilizer application in western Thailand

The default emission factor (EF) of 1.00% for direct nitrous oxide (N₂O) emissions, as recommended by the Intergovernmental Panel on Climate Change (IPCC), is often applied in countries that lack region-specific N₂O EFs, such as Thailand. However, this approach introduces significant uncertainty due to the spatial variability and complex dynamics governing N₂O emissions, potentially leading to inaccurate estimates. This study quantified direct N₂O emissions and derived EFs from chemical fertilizer applications at varying rates (0, 100, 150, 200, and 250 kg N ha⁻¹) in sugarcane plantations located in Kanchanaburi (KB) and Ratchaburi (RB) provinces, western Thailand. The results showed that using nitrogen (N) fertilizer significantly stimulated N₂O emissions at both study sites, with higher N input correlating to greater emissions. The cumulative N₂O emissions for N application rates ranging from 0 to 250 kg N ha⁻¹ varied from 1.16 to 3.85 kg N₂O ha⁻¹ in KB and from 1.33 to 3.90 kg N₂O ha⁻¹ in RB. The calculated N₂O EFs averaged 0.68% (0.66–0.71%) in KB and 0.70% (0.64–0.83%) in RB, with an overall mean EF of 0.69%, representing a 0.31% reduction from the IPCC’s default value. This reduction is relatively attributed to rainfall patterns, soil properties, N application rates, and N utilization by plant in the area. The findings suggest that Thailand’s current national N₂O inventory, based on the default EF, may be overestimated if country-specific EFs resemble the area-specific data observed in this study. While chemical fertilizer application increased N₂O emissions, its role in enhancing soil nutrient availability is essential for boosting crop productivity. Notably, the highest fertilizer input (250 − 75 − 149 kg N − P − K ha⁻¹) did not result in a proportional increase in yield, suggesting that applying fertilizer beyond crop demand may not maximize productivity. Thus, optimizing fertilizer application to match crop nutrient requirements presents a straightforward and practical strategy to reduce N₂O emissions while maintaining food security.