Yield tradeoffs and nitrogen between pennycress, camelina, and soybean in relay- and double-crop systems

Authors: JOHNSON, GREGG - University Of Minnesota; WELLS, SCOTT - University Of Minnesota; ANDERSON, KEVIN - University Of Minnesota; Gesch, Russell - Russ; Forcella, Frank; WYSE, DONALD - University Of Minnesota

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2017
Publication Date: 7/27/2017
Publication URL: https://handle.nal.usda.gov/10113/5801876
Citation: Johnson, G.A., Wells, S.M., Anderson, K., Gesch, R.W., Forcella, F., Wyse, D.L. 2017. Yield tradeoffs and nitrogen between pennycress, camelina, and soybean in relay- and double-crop systems. Agronomy Journal. 109:2128-2135. https://doi.org/10.2134/agronj2017.02.0065.

Interpretive Summary: Farmers in the Upper Midwest are looking for ways to include cover crops that can add economic and environmental benefits to their corn-soybean rotations. Pennycress and winter camelina are winter annual oilseeds that can be grown as cover crops. But, they can also be harvested for their seeds before planting soybean in a double- or relay-crop situation the following summer. The objectives of the present study were to 1) compare differences in oilseed cover crop and soybean yields when both are grown in double- and relay-cropping systems where the oilseeds were either harvested early or late; and 2) determine how the presence or absence of oilseed cover crops affects the levels of inorganic soil nitrogen. The study was conducted at three different sites in MN during 2014 and 2015. Although soybean yields were reduced at one site during 2014 and at all sites in 2015, the addition of an oilseed cover crop in either double- or relay-crop systems resulted in greater total crop production compared with a single soybean crop. The best cropping system to maximize total crop yield depended on environment. The oilseed cover crops yielded the most in the double- and relay-crop systems when they were harvested later rather than earlier. Moreover, pennycress and winter camelina reduced soil nitrogen more than soybean alone, especially during the fall and spring, at which time nitrogen is prone to being lost by leaching into water ways. Pennycress and camelina, when double- and relay-cropped with soybean, increased total crop production, while providing critical ecosystem services like preventing unwanted soil nitrogen loss from the cropping system. Results of this study will benefit agricultural professionals including scientists, ag consultants, and extension specialists who are exploring new cover crops and strategies to maximize cropping system profits while benefiting the environment.

Technical Abstract: To gain additional value from land during winter fallow periods, growers in the Upper Midwest are considering winter annual oilseed crops such as field pennycress (Thlaspi arvense L.) and winter camelina (Camelina sativa L.) as value-added additions to the corn-soybean rotation. The objective of this study was to 1) explore trade-offs between soybean and oilseed cover crop yield as influenced by oilseed harvest timing and soybean planting strategy, and 2) evaluate how inorganic soil N was influenced by the presence or absence of pennycress or camelina. Field experiments were conducted in 2014 and 2015 across three sites in Minnesota to evaluate the yield of field pennycress and camelina oilseed cover crops planted in a double-crop system or planted early or late in a relay-cropping system. Soybean grain yield was reduced in one out of three sites in 2014 and at all sites in 2015. However, the addition of an oilseed cover crop in a relay- or double-crop system increased total crop production. The optimal cropping strategy for achieving maximum total crop yield was dependent on environment. Oilseed cover crop yield tended to be greatest when harvested late rather than early in either a relay- or double-crop system. Pennycress and camelina significantly reduced available N along the entire soil profile compared to soybean alone, especially in the spring and autumn when the potential for N loss is greatest. Pennycress and camelina, when integrated with soybean in a late-planted relay- or double-crop system, increased total crop yield while providing critical ecosystem services.