Environmental factors may influence interseeded annual ryegrass and red clover establishment and growth more than soil residual herbicide applications

Integrating multiple weed management (cultural, physical, chemical) strategies is often recommended to combat herbicide resistance. With the increased use of interseeded cover crops, the effects of PRE herbicides on their establishment and growth require study. An investigation was conducted in Lexington, KY, in 2016 through 2018 to assess the extent to which commonly used PRE corn herbicide combinations influenced interseeded red clover and annual ryegrass establishment and growth. Annual ryegrass density was reduced 29% at 3 wk after interseeding by the combination of residual dimethenamid-P and atrazine; however, biomass the following spring was not affected by herbicide combinations. Neither density of interseeded red clover at 2 to 3 wk after interseeding nor biomass prior to termination the following spring were influenced by herbicide combinations. However, red clover density was affected by herbicide treatment 5 wk after interseeding in 2016. These results could have been influenced by low summer survival, particularly in 2016. The environmental factors may have influenced the survival of the interseeded cover crops more than the PRE herbicides. This study suggests that multiple PRE herbicides can be used with minimal risk to interseeded red clover or annual ryegrass. However, the influence of the environment on establishment and survival of interseeded cover crops following the use of PRE herbicides requires further study.