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Fluid Journal : Fluid Journal 2005-2007
22 Fluid Journal FALL 2007 applications of biologicals evaluated on Roundup Ready crops, possibly because of toxicity of the glyphosate to them. We did, however, obtain a significant 9 bu/A yield response to one mixture of biologicals on late-planted RR corn under rain- fed but not irrigated conditions in northwestern Indiana to indicate a potential benefit to this approach. Biologicals should be selected that are not only effective Mn reducers, but also must be tolerant to glyphosate and its toxic metabolites in root exudates. Detoxifying glyphosate. As little as 2.5 percent of the recommended rate of glyphosate can greatly inhibit uptake and translocation of Fe and Mn by non-target plants (Figure 1). Calcium can help detoxify glyphosate in root exudates; however, Mn in soybean tissue was 6-8 ppm higher with in-furrow Table 2. Effect of zinc application on corn yields and herbicide efficacy. Irrigated* Rain-fed* Yield % weed kill Yield % weed kill Treatment (bu/A) (bu/A) None 132 0 172 0 Glyphosate only 178 100 205 100 Glyphosate + Zn (Tank mix) 143 30 189 30 Zn 15 days after glyphosate 195 100 210 100 * Very heavy weed pressure (grass and broad-leaved weeds), very light weed pressure on the rain-fed plot. Table 1. Effect of Mn and Zn sources on herbicidal efficacy of glyphosate on RR soybeans. Treatment/nutrient source Rate Yield Weed control bu/A % No herbicide* None 46 0 Glyphosate ** 24 oz/A 57 100 Glyphosate + MnCO3 0.5 #Mn/A 75 91 Glyphosate + MnSO4 0.5 #Mn/A 70 93 Glyphosate + Mn EDTA chelate 0.25 #Mn/A 72 100 Glyphosate + Mn AA chelate 0.15 #Mn/A 67 85 Glyphosate + Zn0 0.5 #Zn/A 49 33 Glyphosate + Zn chelate 0.25 #/A 40 40 Glyphosate + ZnO +P 0.5 #/A 41 20 * Heavy weed pressure ** Applied as WeatherMax® formulation at 24 oz/A + ammonium sulfate gypsum than with liming. Corn yields were 10 bu/A higher with in-furrow gypsum under irrigation and also under rain-fed conditions if additional Zn was applied as a seed treatment. Modifying cultural practices. The greatest impact of glyphosate is on low-nutrient-available soils or under conditions that limit nutrient availability. Selection of nutrient efficient varieties or hybrids is especially important since there is a large difference in efficiency within a plant species and this can compensate for some of the reduced efficiency imposed by the glyphosate tolerant gene. Crop sequence, tillage, mulches, soil pH, nitrogen form, and moisture management affect Mn availability. Dr. Huber is professor emeritus in the Botany & Plant Pathology Department, Purdue University. Fluid Journal is sponsored by the Fluid Fertilizer Foundation, a nonprofit organization committed to researching and providing information about fluid fertilizer technology. Since its formation, the FFF has funded over $3 million in fluid fertilizer research. The main goal of Fluid Journal is to transfer this technical information into an easy-to-read format for farmers and dealers, so that they may better understand important advances in the field. FLUID JOURNAL IS PUBLISHED QUARTERLY AND REACHES 12,686 READERS For advertising information and services... Contact Fluid Journal sales coordinator Jeff Tennant at (800)477-1737 E-mail at email@example.com Visit us on the web! www.fluidfertilizer.com • Fertilizer dealers • Crop consultants • Applicators • Distributors • Manufacturers • Academics Plus, large scale farmers in heavy fluid usage areas. Why Advertise in the Fluid Journal?
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