Interaction of Soil Carbon Sequestration and N₂O Flux with Different Land Use Practices

Abstract

The DAYCENT ecosystem model was used to address the feasibility of managing land to sequester carbon in soil after accounting for the greenhouse warming potential of soil N₂O emissions and the CO₂ emissions associated with N fertilizer production. The model simulated the long term changes in soil C levels, N₂O emissions and above ground productivity in agricultural and rangeland systems. The model was run for 100 years of conventional winter wheat/fallow rotations and another 100 years of alternative land use. Simulations showed that corn, corn/alfalfa rotations and silage treatments provide substantial (1.4–1.8 kg C m⁻²) net C storage for the first 25 year period but net C sequestration fell to less than 0.25 kg C m⁻² for the 4^th 25 year period. Conventional tillage and no tillage winter wheat/fallow systems both showed a net input of CO₂ to the atmosphere during each 25 year period after N₂O emissions were considered. Native grassland under ligght to moderate grazing stored small amounts of C but addition of 1 gN m⁻² yr⁻¹ greatly increased net C sequestration in rangeland simulations. All of the practices except unfertilized grassland showed significant inverse correlations between soil C storage and N₂O emissions. We conclude that the large expanses of land in the U.S. Great Plains that have been historically used for winter wheat/fallow rotations could sequester large amounts of C if water were made available for intensive corn, corn/alfalfa or silage agriculture and that rangeland could store significant amounts of C with light N fertilization.