Tillage and cover crop mixtures interseeded in maize-soybean in the upper Midwest

Ecosystem benefits of winter-killed annual cover crops are less studied than winter hardy annuals. The objectives of this study were to determine (1) the effects of tillage practices and cover crop mixtures on biomass and soil cover of cover crops seeded into nearly mature maize (Zea mays L.) and soybean [Glycine max (L.) Merr.] and (2) if cover crop biomass can be estimated from soil surface coverage measurements. The study was conducted within two long-term tillage trials from 2016 to 2018. Tillage included conventional-(CT), strip-(ST), and no-till-(NT). Cover crops included annual ryegrass (AR; Lolium multiflorum L.); AR and crimson clover (CC; Trifolium incarnatum L.) mixture (ARCC); AR, CC, and forage radish (FR; Raphanus sativus L.) mixture (ARCCFR); and no-cover (NC). Seeding rates for AR, ARCC, and ARCCFR were 28, 36, and 40.5 kg ha(-1), respectively. The ARCCFR mix produced the most biomass (256 kg ha(-1)), followed by AR (174 kg ha(-1)) and ARCC (165 kg ha(-1)). Cover crop biomass was 260 and 136 kg ha(-1) in maize and soybean; and 218, 201, and 177 kg ha(-1) in CT, ST, and NT, respectively. Cover crop soil coverage between rows was 25% in maize and 14% in soybean. Cover crop biomass was associated with soil surface coverage (R-2 = 0.841). Given that cover crop biomass drives ecosystem services associated with cover crops, limited biomass and ground coverage of winter killed cover crops seeded into nearly mature maize and soybean may not add ecosystem services in the upper Midwest.