Impacts of cover crop planting dates on soils after four years

Abstract

AbstractImpacts of cover crop (CC) mixes and early CC planting on soil properties, CC biomass production, and CC biomass C input are not well understood. We assessed CC planting date (pre‐ or post‐harvest) and CC type (rye [Secale cereale L.], mix of winter pea [Pisum sativum L.], hairy vetch [Vicia villosa L.], rye, and radish [Raphanus sativus L.], or no CC) effects on soil physical properties, organic matter, and CC biomass C input under three no‐till continuous corn (Zea mays L.) and corn‐soybean (Glycine max L.) sites in the eastern Great Plains after 4 yr. Across sites and years, pre‐harvest‐planted CCs produced 0.81 ± 0.52 (mean ± SD), post‐harvest‐planted 0.59 ± 0.44, rye 0.83 ± 0.52, and mix 0.57 ± 0.42 Mg biomass ha−1. Compared to no CC, pre‐ and post‐harvest–planted CC effects varied by site. Pre‐harvest–planted CCs increased wet‐aggregate stability by 17% and particulate organic matter by 31% under continuous corn at one of three sites compared with post‐harvest‐planted CCs. Similarly, the CC mix had variable effects on cone index but reduced bulk density by 7% at one site under continuous corn and increased wet‐aggregate stability by 21% at another site under corn−soybean. Planting date, but not CC type, effects were slightly more evident under continuous corn than corn−soybean. Across sites and years, pre‐harvest‐plant CC had 0.29 ± 0.38 Mg biomass C ha−1, post‐harvest‐planted 0.22 ± 0.30, rye 0.33 ± 0.37, and the mix 0.16 ± 0.27. Low CC biomass (<1 Mg ha−1) production may explain the limited CC effects. Overall, pre‐harvest‐planted CCs and CC mixes had minimal effects on soil properties in this region after 4 yr.