pH-dependent microbial responses drive nitrous oxide mitigation by the nitrification inhibitor DMPP

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Science

Background:

• Nitrous oxide (N₂O) emissions from agricultural soils are a significant environmental concern, primarily driven by microbial nitrogen transformations after fertilizer application.
• Nitrification inhibitors, such as 3,4-dimethylpyrazole phosphate (DMPP), are explored to mitigate these emissions, but their efficacy varies with environmental conditions.

Purpose of the Study:

• To evaluate the effectiveness of DMPP in reducing N₂O emissions across different soil pH levels in Cyprus.
• To investigate the impact of DMPP on inorganic nitrogen dynamics and soil microbial communities involved in nitrogen cycling.

Main Methods:

• A laboratory microcosm experiment was conducted using four Cypriot soils with varying pH (acidic to near-neutral).
• Soils were treated with control, N-P-K fertilizer, or N-P-K fertilizer with DMPP.
• N₂O emissions, inorganic nitrogen, and the abundance of N-cycling microbial genes (e.g., amoA) were measured.

Main Results:

• DMPP reduced cumulative N₂O emissions by 81%-96% in near-neutral soils by suppressing ammonia-oxidizing bacteria.
• In acidic soils, DMPP showed minimal impact on N₂O emissions and microbial gene abundances.
• Soil pH, ammonium availability, and amoA gene abundance were identified as key predictors of DMPP efficacy and N₂O fluxes.

Conclusions:

• Soil pH is a critical factor determining the effectiveness of nitrification inhibitors like DMPP.
• Site-specific nitrogen management strategies are essential for optimizing fertilizer use and mitigating greenhouse gas emissions from agricultural soils.