Establishing winter annual cover crops by interseeding into maize and soybean

Authors: Mohammed, Yesuf; MATTHEES, HEATHER - Winfield Solutions; Gesch, Russell - Russ; PATEL, SWETABH - Iowa State University; FORCELLA, FRANK - Retired ARS Employee; AASAND, KYLE - North Dakota State University; STEFFL, NICHOLAS - North Dakota State University; JOHNSON, BURTON - North Dakota State University; WELLS, M - University Of Minnesota; LENSSEN, ANDREW - Iowa State University

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2019
Publication Date: 2/6/2020
Citation: Mohammed, Y.A., Matthees, H.L., Gesch, R.W., Patel, S., Forcella, F., Aasand, K., Steffl, N., Johnson, B., Wells, M.S., Lenssen, A. 2020. Establishing winter annual cover crops by interseeding into maize and soybean. Agronomy Journal. 112:719-732. https://doi.org/10.1002/agj2.20062.
DOI: https://doi.org/10.1002/agj2.20062

Interpretive Summary: Cover crop adoption in the upper Midwest, USA, is low mainly due to limited time for their establishment after main crop harvest and additional input costs. Interseeding cover crops early in the vegetative development stages of the main crops (corn and soybean) could result in competition between main crops and cover crops. Late interseeding particularly towards the end of the reproductive stages of corn and soybean could help to avoid this competition. Information on interseeding of new winter annual cover crops such as winter camelina and pennycress into standing corn and soybean during their reproductive development stage is limited. Winter camelina and pennycress are winter annual oilseeds that can be used as cover crops. These oilseeds can be harvested for seeds allowing farmers to double- or relay-crop with soybean. The seeds harvested from camelina and pennycress could help to incentivize producers to compensate the additional input costs. Also, these new crops could help diversify cropping systems. A field experiment at four locations (Ames, IA; Morris and Rosemount, MN; and Prosper, ND) was conducted to determine the best time to interseed cover crops (i.e., pennycress, winter camelina, and winter rye) for successful establishment. We also measured the effects of interseeding cover crops on corn and soybean grain yields and soil water content. Generally, interseeding late in the reproductive stage of soybean and corn produced more cover crop biomass with better green cover that can help protect soil from erosion. Cover crop performance when interseeded into standing corn was challenging due to leaf canopy shading compared with soybean. There was no corn or soybean grain yield loss due to these cover crops or interseeding dates. Producers could seed these cover crops into standing soybean to enhance cover crop adoption and crop diversification. This information will benefit producers interested in growing cover crops, and extension specialists and consultants in advising producers. The information will also benefit other scientists interested in developing best management practices for interseeding cover crops.

Technical Abstract: Cover crops adoption in the upper Midwest USA is low mainly due to limited time for their establishment after main crop harvest and increased input costs. Therefore, alternative seeding options are needed. We evaluated winter annual crops interseeded at different dates into standing maize (Zea mays L.) and soybean [(Glycine max (L.) Merrill)] to determine cover crop establishment success, effects on main crop grain yield and soil water content at four locations: Ames, Iowa; Morris and Rosemount, Minnesota; and Prosper, North Dakota. Treatments included three interseeding dates (R4, R5, and R6 development stages for maize, and R6, R7, and R8 development stages for soybean) and three cover crops [winter camelina (Camelina sativa L.), field pennycress (Thlaspi arvense L.), winter rye (Secale cereale L.)], and a control (no cover crop). The effects of interseeding date on cover crop stand and growth varied across locations and seasons for both maize and soybean systems. By spring, rye tended to produce the greatest green cover and growth across most locations. However, pennycress produced more green cover (40%) than other covers at Prosper in the soybean system. Interseeding date and cover crops did not negatively affect maize or soybean grain yields or soil water content. Generally, cover crop stand and growth were better in soybean than maize due to less leaf canopy shading. This was more evident for the oilseeds (pennycress and camelina) than winter rye. Further research is needed to develop better suited cultivars and/or agronomic management practices for interseeding. The absence of soybean yield loss together with better cover crop establishment indicates that producers could integrate these covers to diversify and add ecosystem services to soybean production practices.