Integrating beef cattle on cropland affects net global warming potential

Authors: Liebig, Mark; FAUST, DEREK - Clover Park Technical College; Archer, David; Christensen, Rachael; Kronberg, Scott; Hendrickson, John; Lee, Joon-Hee; TANAKA, DONALD - North Dakota State University

Submitted to: Nutrient Cycling in Agroecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2021
Publication Date: 5/30/2021
Citation: Liebig, M.A., Faust, D.R., Archer, D.W., Christensen, R., Kronberg, S.L., Hendrickson, J.R., Lee, J., Tanaka, D.L. 2021. Integrating beef cattle on cropland affects net global warming potential. Nutrient Cycling in Agroecosystems. https://doi.org/10.1007/s10705-021-10150-9.
DOI: https://doi.org/10.1007/s10705-021-10150-9

Interpretive Summary: Integrated crop-livestock (ICL) systems could potentially reduce greenhouse gas emissions by sequestering soil organic carbon. However, there is a need to account for all greenhouse gas sources and sinks in ICL systems, particularly in semiarid regions. A study was conducted to determine the net global warming potential (GWP) of grazed and ungrazed cropland at a long-term research site near Mandan, ND USA. Effects on net GWP included carbon dioxide emissions associated with production inputs and field operations, methane emissions from enteric fermentation by beef cattle, changes in soil carbon stocks, and methane and nitrous oxide fluxes from soil. Net GWP was positive for grazed and ungrazed cropland, meaning both production systems were a source of greenhouse gas emissions to the atmosphere. Carbon dioxide emissions associated with seed production and field operations were lower under ungrazed cropland, while soil methane uptake was greater under grazed cropland. Methane emissions from beef cattle were also a large greenhouse gas source from grazed cropland absent in ungrazed cropland. When factors were summed, net GWP was greater under grazed cropland compared to ungrazed cropland. Reducing greenhouse gas emissions from ICL systems may be possible by improving production efficiencies and adopting practice that increase soil carbon storage.

Technical Abstract: Integrated crop-livestock (ICL) systems have the potential to improve agricultural and environmental outcomes. Recent interest in ICL systems have prompted numerous investigations to quantify ecosystem service tradeoffs associated with their 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 study near Mandan, ND USA. Factors evaluated for their contribution to net GWP included CO2 emissions associated with production inputs and field operations, CH4 emissions from enteric fermentation by beef cattle, change in soil carbon stocks, and soil-atmosphere CH4 and N2O fluxes. Net GWP was significantly greater for grazed cropland (946 kg CO2equiv. ha-1 yr-1) compared to ungrazed cropland (200 kg CO2equiv. ha-1 yr-1) (P=0.0331). Among 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). However, the difference in net GWP between treatments was largely driven by emissions from enteric fermentation (602 kg CO2equiv. ha-1 yr-1). As both production systems resulted in net GHG emissions to the atmosphere, adoption of practices that constrain GHG sources and boost GHG sinks under semiarid conditions are needed. Practices that improve system efficiencies and favor high rates of soil carbon accrual are recommended.