Evaluation of soybean selection and sowing date in a continuous cover relay-cropping system with pennycress

Authors: Gesch, Russell - Russ; Mohammed, Yesuf; MATTHEES, HEATHER - Winfield United

Submitted to: Frontiers in Sustainable Food Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2022
Publication Date: 1/10/2023
Citation: Gesch, R.W., Mohammed, Y.A., Matthees, H.L. 2023. Evaluation of soybean selection and sowing date in a continuous cover relay-cropping system with pennycress. Frontiers in Sustainable Food Systems. 6. Article 961099. https://doi.org/10.3389/fsufs.2022.961099.
DOI: https://doi.org/10.3389/fsufs.2022.961099

Interpretive Summary: Pennycress is as a newly domesticated winter annual oilseed crop that can be grown during the fallow period (fall until spring) between the rotation of wheat and soybean. When used in this rotation, the pennycress is planted soon after wheat harvest. The next spring the soybean is interseeded between pennycress rows so that their lifecycles overlap (aka "relay interseeding"). The pennycress is harvested over the top of the soybean in late June and the soybean harvested in the fall. What we don't know is when the best time to relay interseed soybean and the best cultivar to use to optimize soybean yield without reducing pennycress yield. We conducted a two-year field study to answer these questions. We discovered that the best time to relay plant soybean is when the pennycress is in its bolting stage, which generally corresponds to early May in central Minnesota. Also, we found that for relay-cropping soybean into pennycress, soybean yields are optimized by using a normal to slightly longer maturing soybean variety for the region (e.g., west central Minnesota). Using this type of relay-cropping system enables farmers to keep living plant cover on their fields almost year-round, which helps reduce soil erosion, scavenge excess soil nitrogen to reduce its negative impacts on water and air quality, and creates prime habitat and food for pollinators. Results will benefit farmers interested in relay-cropping, university extension specialists, agricultural consultants, and other scientists seeking ways to sustainably intensify crop production.

Technical Abstract: Pennycress (Thlaspi arvense L.) is as a new winter annual oilseed crop that can be integrated as a “cash cover crop” in Midwestern USA cropping systems. Relay-cropping pennycress with soybean [Glycine max (L.) Merr.] has been shown as an effective way to produce three crops over two years while providing living cover on the agricultural landscape year-round. However, management improvements are needed to optimize pennycress and soybean production in this new system. A field study conducted over two growing seasons (2015-2017) in west central Minnesota USA evaluated interseeding date and cultivar of soybean on overall productivity of this relay system. Three relay interseeding dates for soybean, based on pennycress growth stage (S1, rosette stage; S2, bolting stage; and S3, initial flowering), and three soybean cultivars varying in maturity group (MG0.2, MG1.1, and MG1.7), were evaluated in a split-plot design. In the second season, relaying soybean reduced pennycress seed yield compared with its monocrop counterpart, but the reduction was lowest (23%) at SD2. Cultivar maturity group impacted soybean growth and yield in the relay system. Although generally there was soybean yield drag associated with relay-cropping, seed yield of the MG1.7 soybean relay interseeded at SD2 was not significantly different than a monocropped MG1.1 soybean using conventional practice (CP; winter fallow, no pennycress). Results indicate that relay interseeding a standard (MG1.1) to longer maturity (MG1.7) soybean for the region at the bolting stage (SD2) of pennycress optimized overall system productivity while keeping continuous living cover on the agricultural landscape. More research will likely be needed to improve soybean selection and management regionally for this unique relay system.