ALLELOPATHIC POTENTIAL OF SOME WARM-SEASON GRASSES

Aqueous extracts of tissue from the test species (giant foxtail, green foxtail, yellow foxtail, bahiagrass, barnyardgrass, Johnsongrass and large crabgrass) harvested at the vegetative and mature stages were te sted for allelopathy on seed germination and seedling growth of the bi oassay species (alfalfa and Italian ryegrass). Tissues harvested from large crabgrass and barnyardgrass were found not to be allelopathic; o nly tissue harvested from the five other test species during the matur e stage of plant growth exhibited allelopathic characteristics. Extrac ts of stem material reduced seed germination and seedling growth for b oth bioassay species. It was estimated that 0.30/0.33, 0.23/0.18, 0.20 /0.21, 0.31/0.32 and 0.38/0.19% aqueous extracts of mature Johnsongras s, bahiagrass, giant foxtail, green foxtail and yellow foxtail stem ti ssue resulted in a 50% reduction in seed germination/seedling growth o f Italian ryegrass, respectively. Concentrations in a similar range re sulted in 50% reduction in seed germination and seedling growth in the alfalfa bioassay. The potential concentration for foliage tissue in s oil solution of the pasture ecosystem for Johnsongrass, bahiagrass, gi ant foxtail, green foxtail, and yellow foxtail foliage tissue would be 3.2, 1.0, 2.0, 1.4 and 1.4%, respectively. The allelopathic character istics of these species could therefore be of economic importance in t he pasture ecosystem when overseeding the pasture with grass and legum e species.