Corn, soybean, and weed responses to spring-seeded smother plants

Field and greenhouse research was conducted to better define the characteri stics of a spring-seeded smother plant system for weed control in corn (Zea mays L.) and soybean (Glycine max [L.] Merr.). In the greenhouse, emergenc e and early growth of two medic (Medicago) species was greatest when plante d 1.5 cm deep. In the field, Berseem clover (Trifolium alexandrinum L.), fo ur medic species, and yellow mustard (Brassica hirta Moench) were planted i mmediately after corn or soybean planting in a 25-cm-wide band centered ove r the crop row. All species achieved 45% or more ground cover by 72 days af ter planting and yellow mustard often generated ground cover more quickly t han other species. Weed suppression varied, with yellow mustard and Sava me dic (Medicago scutellata L.) often providing greater weed suppression than other species. However, weed suppression was highly variable and crop yield s were usually reduced compared with weed-free plots. Killing Sava medic 30 days after planting reduced weed suppression and did not increase corn yie ld compared with allowing the medic to survive until maturity. Delaying see ding of Sava medic until rotary hoeing increased weed suppression compared with rotary hoeing alone.