Interseeded cover crop mixtures influence soil water storage during the corn phase of corn-soybean-wheat no-till cropping systems

Cover crops (CC) have the potential to increase water storage by reducing runoff, increasing infiltration, and decreasing evaporation. Interseeding CC into a summer cash crop can increase CC biomass production essential for maximizing beneficial services. Effects of interseeded CC on soil water content during the following cash crop has not been fully evaluated in the Mid-Atlantic USA. Soil water content was measured during the corn (Zea mays L.) phase of four no-till rotations at the USDA Beltsville Agricultural Research Center, Beltsville, MD from 2017 through 2020. All systems included corn-soybean (Glycine max L.)-wheat (Triticum aestivum L.) rotations, and Systems 3, 4 and 5 added double crop soybean (DCS) after wheat. In System 5, a mix of rye (Secale cereale L.)hairy vetch (Vicia villosa Roth)-crimson clover (Trifolium incarnatum L.) was interseeded into DCS. In System 6, red clover (rc, Trifolium pratense L.) was interseeded into wheat and rye was planted into rc after wheat harvest. In 2017 and 2018, season average soil water storage was 20 mm greater in systems with CC before corn compared to no CC before corn (NC). A similar, but non-significant, trend was present in 2019 and 2020 (11 mm). Estimated evapotranspiration was lower for CC compared to NC systems in 2018, while greater estimated infiltration was observed for CC compared to NC systems in 2019. Four-year average corn yields were greater for CC compared to NC systems (12.1 vs 10.6 Mg ha-1). Similarly, average corn water use efficiency (WUE) was greater in CC compared to NC systems (5.55 vs 4.70 kg m-3). The returns from increased yield more than offset the cost of CC establishment. The combination of greater yields and WUE demonstrate the benefits of interseeded CC in humid regions of the US.