Derek M. Scroggs1, A. M. Stewart1, D.K. Miller2, B. R. Leonard3, James L. Griffin2, and David C. Blouin4. (1) LSU AgCenter, Dean Lee Research Station, 8105 Tom Bowman Dr., Alexandria, LA 71302, (2) LSU AgCenter, P.O. Box 438, St. Joseph, LA 71366, (3) LSU AgCenter, Macon Ridge Station, 212 Macon Ridge, Winnsboro, LA 71295, (4) LSU AgCenter, Department of Experimental Statistics, Baton Rouge, Baton Rouge, LA 70803
A field study was conducted in 2006 and 2007, along with two outdoor pot studies in 2007 at the Dean Lee Research and Extension Center near Alexandria, LA, to determine if zinc antagonizes glyphosate efficacy. Treatments consisted of a factorial arrangement of glyphosate formulations (isolpropylamine salt, potassium salt, and diammonium salt) and foliar zinc products (No zinc, RSA 7% zinc, and Trafix 10% zinc). Treatments were applied using a tractor mounted compressed air sprayer delivering 140 L/ha using flat fan tips. Weed control was determined at 7, 14, and 28 days after treatment. For the pot study, weed control was determined at 7 and 14 dat and fresh weight was recorded at 14 dat. For the field studies, weeds evaluated in 2006 consisted of pitted morningglory, hophornbeam copperleaf, Palmer amaranth, barnyardgrass, browntop millet, and Johnsongrass, and in 2007 weeds consisted of Palmer amaranth, barnyardgrass, browntop millet, and Johnsongrass. At application, all weeds were small and actively growing. For the pot studies, barnyardgrass, browntop millet, hemp sesbania, johnsongrass, entireleaf morningglory, and redroot pigweed seed were planted at a depth of 2 cm in a 1:1 mixture of peat moss and Latanier silt loam soil and evaluated. Weed control data and fresh weight reduction data were analyzed as a RCB design with a factorial arrangement of treatments with repeated measures over the evaluation intervals. All data analysis was conducted using SAS PROC MIXED procedure with estimates of means and standard errors generated using LS means and experiments designated as random effects in the model.
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