Effects of Postemergence Herbicides on Seedling Development of Selected Legumes

Abstract

Three herbicides were evaluated in a series of growth chamber experiments for possible phytotoxic or growth retarding effects on alfalfa (Medicago sativa L.), crimson clover (Trifolium incarnatum L.), and subterranean clover (Trifolium subterraneum L.) seedlings emerging through a straw mulch treated with the herbicides. After legumes were planted in a coarse, sterile sand and covered with a .25 in. layer of chopped bermndagrass, treatments of Fusilade (0, .125, .25, and .50 lb. a.i.lacre), Roundup (0, .45, .90, and 1.8 lb. a.i.lacre), and Paraquat (0, .25, .50, and 1.0 lb. a.i./acre) were applied. One-half of each herbicide treat-ment received a daily misting while the other received water only as needed to maintain plant health.
A daily misting apparently gave significantly higher emergence percentages compared to the 4-day interval when Paraquat was applied to either crimson or subterranean clover plantings. Herbicide treatment apparently had little or no effect on hypocotyl or radicle elongation of subterranean clover. However, a significant reduction in a radicle length was seen with the Roundup treatment on crimson clover while a similar trend was observed with subterranean clover.