Cover crop (CC) biomass is generally proportional to its ability to provide weed control. In addition, some CC release allelopathic compounds that contribute to weed suppression by inhibiting germination and early growth. In corn-soybean systems, CC are usually established in the fall after corn harvest and terminated prior to soybean planting. However, labor and equipment constraints challenge CC establishment after corn harvest in the western Corn Belt. The objective was to evaluate four spring planted CC with respect to biomass production and weed suppression, concurrent with CC growth and post-termination.