Selective Herbicidal Effects of 2,4-Dichlorophenoxy-Acetic Acid Applied to Turf in Dry Mixtures with Fertilizer

Abstract

Dry mixtures of 2,4-dichlorophenoxyacetic acid (2,4-D) and complete fertilizer (10-6-4) were applied to weedy turf plots on Nov. 6, 1945, and Mar. 22, 1946. The fertilizer was used at the uniform rates of 1, 1.5, 3, 6 and 9 lb. per acre to individual plots. Clippings of weed and grass foliage were collected, hand-sorted, and weighed separately. Fall applications (Nov. 6) of 2,4-D caused almost 100% killing of such weedy spp. as Plantago lanceolata, Medicagolupulina and Tri-folium repens, even at the lowest rate of 2,4-D (1.5 lb. per acre). No significant difference in amt. of grass clippings was found in any of the 2,4-D treatments with fertilizer. Spring applications (Mar. 22) of 6 and 9 lb. per acre of 2,4-D in the fertilizer mixture caused a visible injury to the grass and a reduction in wt. of clippings. At 1.5 and 3 lb. per acre the acid caused no apparent injury to the grass and was effective in killing most of the lawn weeds growing in it. Comparison among the ammonium, sodium, and morpholine salts of 2,4-D applied at the rate of 4 lb. per acre in dry mixture with sand to plots of 1/6 acre indicated that the morpholine salt is less effective than the ammonium or sodium salts of 2,4-D. The use of a small amt. of 2,4-D in the recommended fertilizing practices for turf appears to be an effective way of ridding such areas of weeds so that expensive spraying equipment is not required for applying the selective herbicide.