Long-term no-till and stover retention each decrease the global warming potential of irrigated continuous corn.

Area of Science:

• Agricultural Science
• Soil Science
• Environmental Science

Background:

• Irrigated agriculture has expanded significantly, doubling cultivated land area globally over 50 years.
• Long-term impacts of agronomic management on soil organic carbon (SOC) stocks and greenhouse gas (GHG) emissions in irrigated systems are not well understood.

Purpose of the Study:

• To quantify the effects of residue and tillage management on soil nitrous oxide (N2O) and methane (CH4) fluxes.
• To assess changes in soil organic carbon (SOC) stocks under different management practices in an irrigated continuous corn system.
• To determine the global warming potential (GWP) of irrigated corn systems under various agronomic management strategies.

Main Methods:

• A long-term (since 2002) irrigated continuous corn experiment in Nebraska, USA, was used.
• Treatments included no or high stover removal combined with no-till (NT) or conventional disk tillage (CT).
• Soil N2O and CH4 fluxes were measured over five crop-years (2011-2015), and SOC changes (ΔSOC) were determined to ~30 cm depth.

Main Results:

• Area- and yield-scaled soil N2O emissions were higher with stover retention and CT compared to removal and NT, respectively.
• Methane (CH4) emissions were minimal (<1%), with NT being CH4 neutral and CT a CH4 source.
• Surface SOC decreased with stover removal and CT after 14 years; all systems were net GHG sources when GWP was calculated.

Conclusions:

• Conservation practices (NT, stover retention) individually decreased system GWP compared to conventional practices (CT, stover removal).
• Pairing conservation practices (e.g., NT with stover retention) did not provide additional GWP mitigation benefits.
• Management decisions significantly impact soil GHG emissions and SOC stocks in irrigated systems, providing valuable empirical evidence for sustainable agriculture.