Integrating beef cattle on cropland affects net global warming potential.

Recent interest in integrated crop-livestock (ICL) systems has prompted numerous investigations to quantify ecosystem service tradeoffs associated with management. However, few investigations have quantified ICL management effects on net global warming potential (GWP), particularly in semiarid regions. Therefore, we determined net GWP for grazed and ungrazed cropland in a long-term ICL study near Mandan, ND USA. Factors evaluated for their contribution to net GWP included carbon dioxide (CO₂) emissions associated with production inputs and field operations, methane (CH₄) emissions from enteric fermentation by beef cattle, change in soil carbon stocks, and soil-atmosphere CH₄ and nitrous oxide (N₂O) fluxes. Net GWP was significantly greater for grazed cropland (946 kg CO_2equiv. ha^-1 yr^-1) compared to ungrazed cropland (200 kg CO_2equiv. ha^-1 yr^-1) (P=0.0331). The difference in net GWP between treatments was largely driven by emissions from enteric fermentation (602 kg CO_2equiv. ha^-1 yr^-1). Among other contributing factors, CO₂ emissions associated with seed production and field operations were lower under ungrazed cropland (P = 0.0015 and 0.0135, respectively), while soil CH₄ uptake was greater under grazed cropland (P = 0.0102). Soil-atmosphere N₂O flux from each system negated nearly all the CO_2equiv. sink capacity accrued from soil carbon stock change. As both production systems resulted in net greenhouse gas (GHG) emissions to the atmosphere, novel practices that constrain GHG sources and boost GHG sinks under semiarid conditions are recommended. [ABSTRACT FROM AUTHOR]