Allelopathic potential of winter cereals and their cover crop mulch effect on grass weed suppression and corn development

Field experiments were conducted to study the effect of three rye (Secale cereale L.) populations, six triticale (XTriticosecale Wittm.) cultivars, and two barley (Hordeum vulgare L.) cultivars, used as cover crops, on the emergence and growth of barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.], bristly foxtail [Setaria verticillata (L.) P. Beauv.], and corn (Zea mays L.). Moreover, bioassay studies were conducted to assess allelopathic potential of the winter cereal extracts on both weed species and corn. All winter cereal extracts reduced barnyardgrass and bristly foxtail seed germination and growth, but none of them had any effect on corn. Bristly foxtail was affected more by all extracts than barnyardgrass, and growth of both weed species was reduced more by the extract of barley cultivar Athinaida. In field, 4 wk after corn planting, barnyardgrass and bristly foxtail emergence was reduced by 27 to 80% and 0 to 67%, respectively, in winter cereal mulched plots compared with that in winter cereal mulch-free plots. On the contrary, corn emergence was not affected by any cover crop mulch. At harvest, corn grain yield increased by 45% in no herbicide treated barley cultivar Athinaida mulched subplots as compared with that in respective mulch-free subplots. This corn yield in no herbicide treated Athinaida mulched subplots was similar with that obtained in respective herbicide-treated subplots. The results of this study suggest that some winter cereals such as barley cultivar Athinaida could be used as cover crop for annual grass weed suppression in corn and consequently to minimize herbicide applications.