Soil greenhouse gas emissions from agroforestry and other land uses under different moisture regimes in lower Missouri River Floodplain soils: a laboratory approach

Abstract

Changes in land use management practices may have multiple effects on microclimate and soil properties that affect soil greenhouse gas (GHG) emissions. Soil surface GHG emissions need to be better quantified in order to assess the total environmental costs of current and possible alternative land uses in the Missouri River Floodplain (MRF). The objective of this study was to evaluate soil GHG emissions (CO2, CH4, N2O) in MRF soils under long-term agroforestry (AF), row-crop agriculture (AG) and riparian forest (FOR) systems in response to differences in soil water content, land use, and N fertilizer inputs. Intact soil cores were obtained from all three land use systems and incubated under constant temperature conditions for a period of 94 days using randomized complete block design with three replications. Cores were subjected to three different water regimes: flooded (FLD), optimal for CO2 efflux (OPT), and fluctuating. Additional N fertilizer treatments for the AG and AF land uses were included during the incubation and designated as AG-N and AF-N, respectively. Soil CO2 and N2O emissions were affected by the land use systems and soil moisture regimes. The AF land use resulted in significantly lower cumulative soil CO2 and N2O emissions than FOR soils under the OPT water regime. Nitrogen application to AG and AF did not increase cumulative soil CO2 emissions. FLD resulted in the highest soil N2O and CH4 emissions, but did not cause any increases in soil cumulative CO2 emissions compared to OPT water regime conditions. Cumulative soil CO2 and N2O emissions were positively correlated with soil pH. Soil cumulative soil CH4 emissions were only affected by water regimes and strongly correlated with soil redox potential.