Effect of herbicides on two species of clover underseeded into barley

Potato (Solanum tuberosum L.) producers on Prince Edward Island often under seed red clover (Trifolium pratense L.) into barley (Hordeum vulgare I,.) c rops so as to have a forage crop in the third year of the 3-yr rotation of potatoes-grain-forages. Some producers would like to plant an annual legume that could be underseeded in barley to improve soil organic matter levels in a 2-yr rotation of barley-potatoes. We examined, over 3 yr (1996-1998), the effect of herbicides commonly used in barley on perennial red clover an d annual berseem clover (Trifolium alexandrinum I,.) underseeded in barley. Based on clover plant stand after herbicide application, both red clover a nd berseem were killed by herbicide mixtures containing dicamba and were se verely injured by bromoxynil. Red clover was severely injured by thifensulf uron/tribenuron mixture whereas berseem clover was only slightly injured. M CPA-Na generally caused little injury to either clover species whereas MCPB /MCPA caused less injury to red clover than to berseem clover. Clover yield in the fall reflected level of injury noted during the season.