Monday, November 5, 2007 - 2:00 PM
77-4
Herbicide Effects on Yield and Quality of Roundup Ready Alfalfa in Idaho.
Glenn Shewmaker and Don Morishita. University of Idaho, Univ. of Idaho PO Box 1827, Evergreen Bldg. 315 Falls Ave Box 1827, Twin Falls, ID 83303-1827
Herbicide trials in alfalfa were conducted at Kimberly , Idaho to evaluate weed control, alfalfa yield, and forage quality. Roundup Ready© Alfalfa was sown in 3 m by 9 m plots 5 May 2006 with 4 reps in a randomized complete block. Herbicide treatments were a control; glyphosate 1 at 0.84 kg AI/ha; glyphosate 2 at 1.68 kg AI/ha; imazamox at 0.0526 kg AI/ha with crop oil conc. 1% v/v and ammonium sulfate solution 2.5% v/v; and 2,4-DB at 1.68 kg AI/ha with sethoxydin at 0.526 kg AI/ha and crop oil conc. at 0.38 L/ha. Herbicides were applied 7 June 2006 and 1st cut harvested 17 July. A sub sample of forage was grab-sampled, separated into alfalfa and weeds, oven-dried, and analyzed for forage quality by NIRS. First season (2 cuts) clean alfalfa yields for the glyphosate 1, glyphosate 2, and imazamox treatments were 7.44, 7.95, and 7.17 Mg ha-1, respectively, and were not different. The 2,4-DB treatment produced a significantly lower yield, 5.87 Mg ha-1. The control yielded 5.57 Mg ha-1. Alfalfa composition of first cut total forage, alfalfa + weeds, was 99-100% for glyphosate, lower for imazamox (81%) and 2,4-DB (86%) treatments, which were higher than the control (29%). The forage quality of clean alfalfa was not affected by treatment.