Alfalfa interseeding depresses seedling emergence, shoot development, and silage yield components in diverse maize hybrids

Authors: Grabber, John; PATEL, SWETABH - University Of Minnesota; NORTHUP, CLAIRE - Natural Resources Conservation Service (NRCS, USDA)

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2026
Publication Date: 3/13/2026
Citation: Grabber, J.H., Patel, S., Northup, C. 2026. Alfalfa interseeding depresses seedling emergence, shoot development, and silage yield components in diverse maize hybrids. Agronomy Journal. http://dx.doi.org/10.1002/agj2.70327.
DOI: https://doi.org/10.1002/agj2.70327

Interpretive Summary: Corn grown as a companion crop for the establishment of interseeded alfalfa usually produces less grain and forage than corn grown alone and this limits the profitability of forage production for dairy farms. The purpose of this two-year study in Wisconsin USA was to gain a greater understanding of how interseeded alfalfa alters the growth and development of corn. Eleven corn hybrids were purchased from several seed companies and grown alone or with interseeded alfalfa. Corn hybrids responded similarly to alfalfa by delaying seedling emergence and flowering and by reducing the growth of stems, leaves, and kernels. Corn grown with alfalfa also had a lower tissue concentration of nitrogen (a key nutrient needed for plant growth), tended to wilt more readily during dry growing conditions, and had a lower yield of forage and grain at harvest. Our results indicate competition for nutrients, and possibly chemical cues or the quality of reflected light from alfalfa, may trigger reduced growth of corn. Reductions in corn growth and yield with alfalfa were, however, less pronounced than previously reported for corn grown in the presence of weeds. Additional studies are needed to identify crop management practices or other approaches that will improve the growth and production of corn grown in this cropping system.

Technical Abstract: Depressed biomass yield of maize (Zea mays L.) grown as a companion crop for alfalfa (Medicago sativa L.) establishment limits the profit potential and adoption of this intercropping system by farms. A two-year field trial in southcentral Wisconsin USA assessed changes in plant development from seedling emergence in May to silage harvest in September of eleven hybrids from five breeding companies that were either sown alone or sown concurrently with alfalfa. Precipitation was 25% below normal in both years, with rainfall concentrated prior to the R1 stage during 2020 but more uniformly distributed during 2021. Maize interseeded with alfalfa more frequently exhibited lower soil water content and greater leaf wilting than solo seeded maize. Although production year influenced trait expression, hybrids responded similarly to interseeding of alfalfa. Interseeding of maize delayed seedling emergence and flowering, reduced chlorophyll levels, N nutrition index, plant height, basal stem area, leaf area, stalk mass, ear diameter and length, and kernel rows per ear, and reduced either kernel number or mass per kernel. Total biomass, grain, and stover yield at harvest were 14% lower in 2020 and 22% lower in 2021 for interseeded maize than for solo-seeded maize. The results demonstrate that interseeded alfalfa delayed or reduced the development of nearly all measured stover and grain traits across a diverse set of maize hybrids. The data suggest the depressive effect of alfalfa on maize were driven in part by through competition for N and water and possibly through plant signaling mechanisms.