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Doing the Math to Meet the XtendiMax, FeXapan, and Engenia Label Application Requirements

The recently EPA approved soybean labels for XtendiMax w/VGT, FeXapan wVGT, and also for Engenia have specified restrictions on certain sprayer operation parameters.  For instance, each label specifies a minimum of 10 GPA, a maximum travel speed of 15 MPH, and also suggests or recommends a maximum operating pressure (63 psi for XtendiMax and though not listed, similar for Engenia).  Originally, the nozzle to use was specified as the TTI 11004.  As of now, there are additional nozzle types and orifice size options.  Additional tankmix items have also been added to the list.  Please check the specified web pages for each product regularly, as there is potential for daily updates.

In order to help applicators (those making decisions) and spray machine operators understand what limitations these specifications place on making applications to DT crops, I have completed two tables doing the math for the various options that would be possible.  Speed and pressure are typically used to determine the operating parameters for any give application scenario.  That will not change, but because of the restrictions on the label, the flexibility in making the applications will be severely limited for each of those parameters.

The tables will show the results of the calibration math for the GPA, MPH, and PSI options.  The calculations are for the TTI 11004 (or any 04 orifice) and are based on 15 and 20-inch nozzle spacings.  The results will be different for each nozzle spacing. The formulas used to determine GPM and PSi are footnoted in the table.  The acceptable combinations are based on a pressure range considered appropriate (by the author) or otherwise specified in the label.  For the TTI nozzle type or other venturi nozzle types, I am using a pressure range of 45 - 65 psi.  The table also has a lower speed limit of 10 MPH, but certainly a lower speed could be used, which would allow for using higher GPA's.  Just insert the speed desired below 10 MPH, do the math, and determine the proper fit for the pressure restrictions.

Since additional nozzles have been added as approved, you will need to do the math for each orifice size to determine the operating parameters.  The math does not change, except for the flow rates based on the desired orifice size.  I have a concern regarding the lower range of the pressures that are published with these new nozzle charts,  It is possible for venturi nozzle designs at lower pressures to have a poor pattern and also too large a droplet.  Either may end up with inadequate coverage on the target, reducing the effective of the application.  To me that will not be good for the success of these herbicide technologies.

Using the University of Illinois Smart Phone or Tablet App - SPRAYER CALIBRATION CALCULATOR, is a very efficient way to complete all the necessary calculations for this table or any other similar calibrations needs such as this.  This app is available through Google Play or the App Store on your phone or tablet.

Link to Doing the Math Chart for a 15 and 20-inch nozzle spacing with an 04 orifice.