Effect of Enhanced Efficiency Fertilizers on Nitrous Oxide Emissions and Crop Yields: A Meta-analysis

Enhanced efficiency fertilizers (EEFs) have the potential to reduce N2O emissions and improve crop productivity, but the impact of soil and management conditions on their effectiveness is not clear. We conducted a meta-analysis to evaluate the effectiveness of different EEF types in reducing N2O emissions in three cereal production systems: rice (Oryza sativa L.), corn (Zea mays L.), and wheat (Triticum aestivum L.). We also compared EEF efficacy across soil and management conditions for corn and wheat systems. Results showed that the effect of EEFs on N2O emissions and crop yields varied greatly with their modes of action, soil types, and management conditions. Nitrification inhibitors (NIs), double inhibitors (DIs: urease plus nitrification inhibitors), and controlled-release N fertilizers (CRFs) consistently reduced N2O emissions compared with conventional N fertilizers across soil and management conditions (grand mean decreases of 38, 30, and 19%, respectively). The Dls more effectively reduced N2O emissions in alkaline soils than did Nls, but the trend was reversed in acidic soils. Urease inhibitors also reduced N2O emissions compared with conventional N fertilizers in coarse-textured soils and irrigated systems. Overall crop yields increased by 7% with the addition of Nls alone. Compared with conventional N fertilizers, Dls also increased crop yields in alkaline soils, coarse-textured soils, and irrigated systems. However, CRFs had no effect on crop yields. Overall, this study suggests that Nls or Dls can reduce N2O emissions while improving crop yields. Growers should select EEFs based on their soil and management conditions to maximize their effectiveness.