Effect of Herbicides on Production and Protein Levels in Pasture Grasses1

Abstract

AbstractField studies were conducted to evaluate the effects of spring application of picloram (4‐amino‐3,5,6‐trichloropicolinic acid), tebuthiuron (N‐[5‐(1,l‐dimethylethyl)‐1,3, 4‐thiadiazol‐2‐yl] ‐N,N′‐dimethylurea), 2,4‐D (isopropyl amine of (2,4‐dichlorophenoxy)acetic acid), and glypho‐ sate (N‐[phosphonomethyl]glycine) on five grasses. The grasses were Common and ‘Coastal’ bermudagrass (Cynodon dactylon (L.) Pers.), kleingrass (Panicum coloratum L.), buffelgrass (Cenchrus ciliaris L.) and an F1 apomictic buffel × birdwood (Cenchrus setigerus Vahl.) hybrid. Grasses were grown in soils classified as either a vertic albaqualf (bermudagrasses) or vertic haplustoll (klein‐ grass, buffelgrass, buffel × birdwood hybrid). All grasses tolerated (with regard to productivity) rates up to 2.2 kg/ha of 2,4‐D applied at all dates, and March applications of glyphosate. Common bermudagrass and klein‐ grass were tolerant to March and April applications of tebuthiuron, with later applications (June) causing reduced production. Coastal bermudagrass was tolerant to tebuthiuron applied in March but not April or June. The only adverse effects of picloram were noted for March applications to Common bermudagrass and all dates for Coastal bermudagrass. The herbicides used had little effect on protein concentration in Coastal bermudagrass. Picloram, tebuthiuron and 2,4‐D reduced protein concentrations in the buffel × birdwood hybrid. Glyphosate caused increases in protein levels in buffelgrass and kleingrass.