Can pulse crops play a role in mitigating greenhouse gases from North American agriculture?
The atmospheric buildup of greenhouse gases (GHGs) is a serious environmental issue. Globally, agricultural activities are an important source of anthropogenic GHGs, contributing 20% of the annual atmospheric increase. Management choices largely determine if agricultural soils will be a source, a sink, or will be neutral with respect to GHG net flux. The proportion of agricultural land that is seeded to pulse crops in the Northern Great Plains (NGP) region of North America has been increasing rapidly over the past decade. Introducing pulses into cereal-based cropping systems could influence the net GHG balance of those systems because pulse crops are thought to stimulate soil-emitted N2O, have different pesticide and fertilizer requirements, and the quality and quantity of their residues vary substantially compared with cereal crops. In this paper we briefly review the available literature, and discuss the potential impact of pulse crops on the net flux of CO2, N2O, and CH4 from soils, and the CO2 emissions associated with energy inputs for cropping systems in the NGP. We also calculate net GHG balances for two example sites. Estimating the final GHG outcome of introducing pulses into cereal-based cropping systems is still uncertain, but current information suggests that replacing a cereal with a pulse crop will likely result in no change or a small but positive net GHG benefit (lower emissions to the atmosphere) for crop rotations in the NGP region.