The environmental impact of ecological intensification in soybean cropping systems in the U.S. Upper Midwest

Authors: CECCHIN, ANDREA - North Dakota State University; POURHASHEM, GHASIDEH - North Dakota State University; Gesch, Russell - Russ; Mohammed, Yesuf; PATEL, SWETABH - Iowa State University; LENSSEN, ANDREW - Iowa State University; BERTI, MARISOL - North Dakota State University

Submitted to: Sustainability
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2021
Publication Date: 2/4/2021
Citation: Cecchin, A., Pourhashem, G., Gesch, R.W., Mohammed, Y.A., Patel, S., Lenssen, A.W., Berti, M.T. 2021. The environmental impact of ecological intensification in soybean cropping systems in the U.S. Upper Midwest. Sustainability. 13(4). Article 1696. https://doi.org/10.3390/su13041696.
DOI: https://doi.org/10.3390/su13041696

Interpretive Summary: Cover crops can reduce the environmental impact of conventional soybean cropping systems. Winter camelina and pennycress are winter-hardy oilseeds. We evaluated these crops as cash producing cover crops to compare them with the most common cover crop, winter rye, on water pollution (eutrophication) potential and soil erosion. In the first year, these cover crops were interseeded into standing soybean. In the second year, soybean was interseeded into winter camelina and pennycress, but winter rye was terminated just before soybean seeding. When the environmental impacts were expressed per ha year-1, cover crops showed lower water pollution potential and soil erosion than the control. In addition, cover crop shows a lower global warming potential when the cover crop did not receive additional N-fertilization. However, when the economic component was included in the assessment, and the results expressed per $ net margin, cover crops significantly reduced their performance in all categories of impact considered. A further optimization of field management for camelina and pennycress is recommended to make the cropping system more sustainable. This information is valuable to researchers and agricultural extension specialists who are focused on developing better management practices for establishing cover crops in the traditional corn-soybean rotation used in the US Corn Belt.

Technical Abstract: Introducing cover crops is a form of ecological intensification that can potentially reduce local, regional and global environmental impacts of soybean cropping systems. An assessment of multiple environmental impacts (global warming potential, eutrophication, soil erosion and soil organic carbon variation) was performed on a continuous soybean system in the U.S. upper Midwest. Four sequences were assessed and compared: a soybean cropping system with winter camelina, field pennycress, or winter rye as cover crop, plus a control (sole soybean). Cover crops were interseeded into standing soybean in Year 1, while in Year 2 soybean was relay-cropped into standing camelina or pennycress. Rye was terminated before sowing soybean. When compared with the control, sequences with cover crops showed lower eutrophication potential (4–9% reduction) and soil erosion (5–32% reduction) per ha year-1, in addition to a lower global warming potential (3–8% reduction) when the cover crop was not fertilized. However, when the economic component was included in the assessment, and the results expressed per USD net margin, the sequences with cover crops significantly reduced their performance in all categories of impact considered. A further optimization of field management for camelina and pennycress is recommended to make the cropping system more sustainable.