Increasing soil pH reduces fertiliser derived N2O emissions in intensively managed temperate grassland

Summary

This 8-year field trial in intensively managed temperate grassland demonstrates that soil pH is a significant driver of fertiliser-derived nitrous oxide emissions, with liming reducing cumulative N2O emissions by up to 39% compared to unlimed controls. Extractable soil phosphorus enhanced yields but had no direct effect on N2O emissions or their yield-scaled equivalents. The authors estimate that recent soil pH increases across Irish grasslands have already reduced national N2O emissions by approximately 95 Gg CO2-eq annually, with potential for further substantial reductions if remaining acidic soils are brought to optimal pH.

UK applicability

The findings are directly applicable to UK grassland management, as soil acidification is a widespread issue in temperate pastoral regions with similar management intensities. The research provides quantified evidence supporting liming as a cost-effective mitigation strategy for reducing agricultural greenhouse gas emissions, with potential implications for UK climate targets and agro-environmental schemes.

Key measures

Cumulative N2O emissions (kg ha−1); N2O emission factors (g N2O-N per kg fertiliser N applied); yield-scaled N2O emissions (g N2O-N per kg grass dry matter); soil pH (range 5.1–6.9); extractable soil phosphorus (2.3–8.3 mg kg−1); grass yields; soil mineral nitrogen

Outcomes reported

The study measured cumulative N2O emissions, soil mineral nitrogen, and grass yields across plots with varying soil pH (5.1–6.9) and extractable phosphorus over a 12-month period following 8 years of liming and phosphorus fertilisation treatments. Results demonstrated a negative linear relationship between soil pH and N2O emissions, with quantified reductions in direct and yield-scaled emissions.

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