Strategies for mitigating nitrous oxide emissions from weathered soils fertilized with urea

Various strategies, particularly those that affect nitrogen (N)-related processes at the soil plant interface, have been investigated to enhance N-agronomic efficiency (AE) and reduce nitrous oxide (N₂O) emissions from soils fertilized with urea, the main N source employed in Brazilian agriculture. This study aimed to evaluate the AE and the N₂O emissions from soils cultivated with maize in soybean-maize succession following treatment with different mitigation approaches in Southern Amazon. An experiment of randomized block design was performed involving seven treatments in which maize was cultivated in soil: (T1) under control conditions; (T2) inoculated with nitrogen-fixing bacteria (NFB); (T3) fertilized with urea; (T4) inoculated with NFB and fertilized with urea; (T5) fertilized with urea containing the nitrification inhibitor dicyandiamide (DCD); (T6) fertilized with urea containing the urease inhibitor N-(n-butyl)thiophosphoric triamide (NBPT); (T7) fertilized with urea containing a combination of DCD and NBPT. The highest N₂O fluxes (300 µg N₂O-N m⁻² h⁻¹) were recorded for T3 and T4 around 12–14 days after top dressing fertilization with urea. Application of DCD-containing urea (T5 and, to a lesser extent, T7) was effective in reducing N₂O emissions. Emission factors were below of 1% for all treatments, with the highest values (≤ 0.42%) recorded for T3, T4 and T6. Fertilization with urea containing DCD alone or in combination with NBPT (T5 and T7) improved the grain yield, the AE, the yield-scaled N₂O and reduced emission factors values by around 75% to the level registered for T3. Use of nitrification inhibitors represents an alternative for the mitigation of greenhouse gas emissions during the off-season maize cropping cycle in Southern Amazon.