Energy use and greenhouse gas emissions in organic and conventional grain crop production: accounting for nutrient inflows

Authors: HOFFMAN, ERIC - University Of Maryland; Cavigelli, Michel; GUSTAVO, CAMARGO - Pennsylvania State University; MATTHEW, RYAN - Cornell University; ACKROYD, VICTORIA - University Of Maryland; RICHARD, TOM - Pennsylvania State University; Mirsky, Steven

Submitted to: Agriculture Ecosystems and the Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2018
Publication Date: 2/8/2018
Citation: Hoffman, E., Cavigelli, M.A., Gustavo, C., Matthew, R., Ackroyd, V.J., Richard, T.L., Mirsky, S.B. 2018. Energy use and greenhouse gas emissions in organic and conventional grain crop production: accounting for nutrient inflows. Agriculture Ecosystems and the Environment. 162:89-96.

Interpretive Summary: Lowering the energy requirements of and greenhouse gas (GHG) emissions from agricultural systems are important climate change mitigation strategies for addressing climate change. Most approaches for estimating the impacts of agricultural management on energy use and GHG emissions simulate potential cropping systems. We used an existing long-term cropping system experiment to link actual measures of cropping system performance with estimates of total system energy use and GHG emissions using the Farm Energy Analysis Tool (FEAT). We quantified energy use and GHG emissions of five cropping systems that comprise the Farming Systems Project (FSP) at the USDA-Agricultural Research Service in Beltsville, Maryland, US. The FSP consists of five grain cropping systems that mimic those used in the mid-Atlantic region of the US: 1) a 3-yr conventional no-till corn (Zea mays L.) –soybean (Glycine max (L.) Merr) – wheat (Triticum aestivum L.)/soybean rotation (NT), 2) a 3-yr conventional chisel-till corn–soybean–wheat/soybean rotation (CT), 3) a 2-yr organic corn–soybean rotation (Org2), 4) a 3-yr organic corn–soybean–wheat rotation (Org3), and 5) a 6-yr organic corn–soybean–wheat–alfalfa (Medicago sativa L.) rotation (Org6). Energy use was greatest in the conventional systems. Greenhouse gas emissions were higher in the Org2 and Org3 systems than in the conventional systems and were lowest in Org6. Our results indicate that organic management has lower energy use than conventional management but that diversifying grain cropping systems to include perennials is a more important management strategy than organic management per se to reduce GHG emissions in agriculture. Our work has expanded the FEAT model to include poultry-based cropping systems and accounts for the nutrients used in organic systems (via manure application) that derive from conventional cropping systems. This analysis will be useful for educating researchers, policy makers, and agricultural professionals on the factors driving energy use and GHG emissions in diverse cropping systems. The expansion of the FEAT model will also be useful to future assessments of cropping systems that rely on poultry litter as a nutrient source.

Technical Abstract: Agriculture is a large source of greenhouse gas (GHG) emissions with large energy requirements. Previous research has shown that organic farming and conservation tillage practices can reduce environmental impacts from agriculture. We used the Farm Energy Analysis Tool (FEAT) to quantify the energy use and GHG emissions of five cropping systems that comprise the Farming Systems Project (FSP) at the USDA-Agricultural Research Service (ARS) in Beltsville, Maryland, US. The FSP consists of five grain cropping systems that mimic those used in the mid-Atlantic region of the US: 1) a 3-yr conventional no-till corn (Zea mays L.) –soybean (Glycine max (L.) Merr) – wheat (Triticum aestivum L.)/soybean rotation (NT), 2) a 3-yr conventional chisel-till corn–soybean–wheat/soybean rotation (CT), 3) a 2-yr organic corn–soybean rotation (Org2), 4) a 3-yr organic corn–soybean–wheat rotation (Org3), and 5) a 6-yr organic corn–soybean–wheat–alfalfa (Medicago sativa L.) rotation (Org6). We accounted for nutrient inflows into organic systems by using the mass-energy allocation method, which accounts for the total energy and GHG emissions from the original production of nutrients found in poultry litter through synthetic fertilizer production (N) and nutrient mining (P and K). We believe this is the first attempt to quantify the energy use and GHG emissions from nutrients used in organic systems that originated through industrial processes used in conventional agriculture. Energy use was greatest in the conventional systems. Greenhouse gas emissions were higher in the Org2 and Org3 systems than in the conventional systems and were lowest in Org6. Our results indicate that organic management has lower energy use than conventional management but that diversifying grain cropping systems to include perennials is a more important management strategy than organic management per se to reduce GHG emissions in agriculture.