Abstract Depressed silage 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. Our objective was to assess whether the interseeding of alfalfa triggered a universal reduction in the development of shoot traits in a diverse set of 11 maize hybrids from five seed companies sown for 2 years in southcentral Wisconsin, USA. 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 the interseeding of alfalfa. The interseeding of maize delayed seedling emergence and flowering; reduced chlorophyll levels, 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 silage 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 seedling emergence and reduced the development of essentially all measured stover and grain traits across a diverse set of maize hybrids. The data suggest the depressive effect of alfalfa on maize was driven in part by competition for N and water and possibly through plant signaling mechanisms.
Grabber et al. (Sun,) studied this question.