Manure application magnifies methane emission from drainage ditch sediments

Area of Science:

• Environmental Science
• Agricultural Science
• Climate Science

Background:

• Agricultural drainage ditches are significant sources of greenhouse gases (GHGs) like methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O).
• Fertilizer inputs from adjacent fields increase nutrient and organic carbon availability in ditch sediments, enhancing GHG production.

Purpose of the Study:

• To quantify the impact of manure and artificial fertilizers on GHG dynamics in agricultural drainage ditch sediments.
• To assess GHG production and oxidation under both oxic and anoxic conditions with varying fertilizer types and doses.

Main Methods:

• Measured potential sediment N2O production, CH4 production, and aerobic CH4 oxidation rates.
• Applied different doses of manure and artificial fertilizer to sediment samples under controlled oxic and anoxic conditions.

Main Results:

• Manure additions strongly stimulated CH4 and N2O production, increasing rates by approximately threefold and 16-fold, respectively.
• Manure also stimulated aerobic CH4 oxidation, though high concentrations led to a decline.
• Artificial fertilizer inhibited CH4 and N2O production and CH4 oxidation even at low doses.
• Under anoxic conditions, high manure inputs increased total GHG emissions (CO2-equivalents) by 3.5 times compared to controls, with methane being the dominant gas.

Conclusions:

• Manure application is a key driver of increased GHG emissions from agricultural drainage ditches.
• Artificial fertilizers have an inhibitory effect on these emissions.
• Implementing climate-smart water and nutrient management strategies is crucial for mitigating climate impacts associated with agricultural practices in ditches and surrounding areas.