Effect of organic fertilizer application on oat–silage maize yield and N₂O emissions

In this study, we aimed at clarifying how organic fertilizer application affects yield and nitrous oxide (N₂O) emissions in an oat (Avena sativa)-silage maize (Zea mays) system. Therefore, we set up six organic fertilizer application gradients: 0, 30, 60, 90, 120, and 150 t·ha⁻¹ (marked as CK, T₁～T₅ respectively). We determined the field N₂O emission flux by static chamber and gas chromatography, combined with soil inorganic nitrogen, temperature and moisture, nitrification potential, denitrification capacity, and crop yield assessment for a comprehensive analysis, to establish the optimal organic fertilizer amount for achieving a high yield and emission reduction as well as to reveal the main factors affecting N₂O emission. The results showed that with the increase in organic fertilizer amount, the cumulative annual N₂O emissions were increasing and then declining, with the trend of T₄ > T₅ > T₃ > T₂ > T₁. The cumulative N₂O emission in silage maize season was higher in the T₁ to T₅ treatments than in the oat season. Soil nitrification potential was increasing, then declining and soil denitrification capacities increased with increasing organic fertilizer amounts. The denitrification capacity was higher in the silage maize season than in the oat season. The T₃ treatment had the highest annual yield of oat−silage maize compared with other treatments (P < 0.05). Soil temperature, moisture, and NH₄⁺-N content were the main factors affecting N₂O emissions. In conclusion, an organic fertilizer application rate of 90 t·ha⁻¹ would be optimal to improve crop yields and reduce N₂O emissions in an oat-silage maize system.