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  • Rickinreallife's picture
    Rickinreallife
    03.17.2014
    There have been repeated assertions that glyphosate resistant crops are "drenched", "doused", "sprayed with massive amounts" etc of glysophate. You can put the amount actually applied in some perspective. Using a Perdue University extension publication "Understanding Glysophate to Increase Performance" [http://www.extension.purdue.edu/extmedia/GWC/GWC-2.pdf], the highest rate of application recommended for three examples on page 5 of the document was for late season control of Ivyleaf Morningglory, at 60 oz./acre of the Roundup Weathermax formulation. The actual active ingredient in Roundup (i.e. glysophate) is for ease of calculation purposes about 1/2 the product by weight (it is usually a smaller percentage). There are 4840 square yards in an acre. At application rate of 60 oz / acre, that is 12/1000th of an ounce per square yard. Since glysophate is only 1/2 of the product, the amount of glysophate applied per sq. yd. would be 6/1000th of an ounce. You would be applying about an ounce of glysophate on an area of about 167 square.

    Another way to look at it, this link is to an article that discusses typical corn seeding and harvest population rates for both dryland and irrigated corn in Nebraska [Row Spacing and Seeding Rate Recommendations for Corn in Nebraska --http://ianrpubs.unl.edu/epublic/pages/publicationD.jsp?publicationId=1591]. Note the average plant population at harvest is 29,000 plants / acre for irrigated, and 21,850 plants / acre for dryland corn. Take the sixty ounces of Roundup in the highest application rate from the Perdue study discussed above, divide that in half to reach 30 ounzes / acre active ingredient. Now, divide 30 oz by 29,000 plants to arrive at .001 oz / plant (or 1 oz per thousand plants) in irrigated corn assuming 100% of the application falls only on corn or in some manner makes its way into the corn crop even if not applied directly to the corn. Now suppose as much as 1/2 of the sprayed product falls on the growing corn or migrates to the corn (a high assumption), that is .0005 oz glysophate per plant. The numbers for dryland are .0013 ozs per plant (assuming 100% applied product is absorbed by corn) or .000565 ozs per plant (assuming 50 %).
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