Multispecies cover crops in organic agricultural systems in the upper U.S. Midwest

Abstract

Abstract Establishing cover crops (CCs) in organic systems for the upper Midwest can be a challenge due to shorter growing seasons. The aim of this systems study was to compare CC management implemented in a tilled organic system. The main crops were oat (Avena sativa L.), corn (Zea mays L.), and soybean [Glycine max (L.) Merr.]. Winter hardy (WH) or winter kill (WK) CC mixes were planted after oat, and red clover (Trifolium pratense L.) was planted into oat for the control treatment. The CCs were planted into corn (WH, WK) or after corn harvest (rye [Secale cereale L.], control). Turnip (Brassica rapa L. ssp rapa) were planted after or into soybean (6–17 kg ha–1). Main crop yields were not affected, but CCs performed poorly in corn and soybean for both fall and spring due to dense main crop canopy, dry surface soil, late harvest, and cold fall temperatures. The CC biomass production was greatest following oat because of the longer growing season but still did not establish well as the red clover control needed to be replanted both in 2018 and 2019. Photographic analyses to calculate leaf area index, ground cover, and evapotranspiration revealed few treatment differences throughout the study, which were more likely caused by weather conditions rather than differences in the WH, WK, and control management practices. These findings further demonstrate the difficulties of consistently establishing CC in corn–soybean rotations for the upper Midwest and highlight the need for developing new strategies.