Location: Agricultural Systems ResearchTitle: Greenhouse gas emissions under winter wheat-based organic and conventional crop productions
|HATFIELD, PATRICK - Montana State University
|RAGEN, DEVON - Montana State University
Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2020
Publication Date: 4/6/2021
Citation: Sainju, U.M., Hatfield, P.G., Ragen, D.L. 2021. Greenhouse gas emissions under winter wheat-based organic and conventional crop productions. Soil Science Society of America Journal. 2021:1-13. https://doi.org/10.1002/saj2.20209.
Interpretive Summary: The impact of sheep grazing used to manage weeds in organic cropping systems on greenhouse gas (GHG) emissions is not clear. Researchers at ARS, Sidney, MT in collaboration with Montana State University found that carbon dioxide and nitrous oxide (major GHGs) emissions were lower with sheep grazing in the organic crop production with no chemical input under winter wheat-based cropping systems compared to the conventional crop production minimum with tillage and chemical inputs. Methane emissions was minimal with little impact of treatments. As a result, global warming potential (GWP) was also lower with sheep grazing in organic farming. Producers can reduce greenhouse gas emissions by using sheep grazing in organic winter wheat-based cropping systems in the northern Great Plains.
Technical Abstract: Sheep (Ovis aries L.) grazing is one of the common practices used to manage weeds in dryland cropping systems, but its impact on greenhouse gas (GHG) emissions is not clear. This study examined sheep grazing during fallow periods in the organic cropping system (SGO) compared to minimum tillage with chemical inputs (MTC) on GHG emissions in three cropping sequences of a 5-yr crop rotation from 2013-2014 to 2015-2016 in the northern Great Plains. Cropping sequences were lentil (Lens culinaris L.) after winter wheat (Triticum aestivum L.) (L-W), winter wheat after sweet clover (Melilotus officinalis L.) cover crop (W-C), and winter wheat after lentil (W-L); crop rotation was safflower (Carthamus tinctorius L.)/sweet clover cover crop–sweet clover cover crop–winter wheat–lentil–winter wheat. The CO2 and N2O fluxes peaked immediately following tillage, planting, fertilization, intense precipitation, and snowmelt, but CH4 uptake increased in the autumn. Cumulative CO2 flux was lower with SGO than MTC for W-C in 2014-2015 and for W-L in 2015-2016. Cumulative N2O flux was also lower with SGO than MTC for W-C in 2014-2015, but was greater with SGO than MTC for L-W in 2015-2016. Treatments did not affect cumulative CH4 flux. The global warming potential (GWP) was lower with SGO than MTC for W-C in 2014-2015 and for W-L in 2015-2016. Sheep grazing for weed control in the organic cropping system may reduce GHG emissions under winter wheat following clover cover crop and lentil compared to the conventional cropping system using minimum tillage and chemical inputs.