Sprayed Weeds in the Yard


4/20/2021 – Last year’s spraying the lawn with Weed Free Zone worked well but we have a lot of Florida Betony, Spider Wort, and more back this year. We did not spray before the greening of the grass so will do so now that it is more mature. The plans below begin with calibrating the little sprayer with the replacement pump that is an 80 psi and not the 40 psi of the original one that froze this past winter.

Calibration Plan of the sprayer that now has an 80-psi pump

Followed the advice here and the advice at https://edis.ifas.ufl.edu/pdffiles/WG/WG01300.pdf where they calibrated a sprayer with the “1/128 method”. That method extrapolates the discharge based on 1/128 measurements and requires conversion from gallons per acre to ounces per 1000 SF. That extrapolation is unnecessary if the test area used is 1000 SF and the collection quantity is in ounces. Therefore, the following steps were taken.

  1. Tested the swath width for the 80 psi pump. The 40 psi pump provided a 40″ swath but the 80 psi pump provided an overall 72″ width with full coverage over a 60″ width. So, divide 1000 SF by the 5′ (60″) actual width. The travel distance to be timed will be 200 feet.
  2. As my sprayer only has one nozzle and the WFZ application is in oz/1000 SF, measured the time it takes to drive across 1000 SF then measured the discharge for that time. The discharge is the volume to add the 1 oz. of WFZ so 1 oz. is applied to 1000 SF.
  3. With the throttle set at a marked rate and the “pedal to the metal” measured travel time for a 5 ft. swath x 200 ft. travel. Repeated three times and each was 33 seconds. That will be the time to spray 1,000 SF.
  4. Then caught the discharge in a clean spray tank for 33 seconds the tank was filled to about 3/8 of a gallon. Caught the discharge for a second 33 seconds and the level was up to 1.5 gallons. Therefore, the sprayer sprays 3/8 of a gallon in 33 seconds; i.e. the travel time for 1,000 SF sprayed.

Areas to be sprayed and the plan

  1. The label’s application range of WFZ is 0.75-1.5 oz./1000 SF.
  2. For this treatment, we will apply 1.25 oz. per 1000 SF by adding that much to 3/8ths of a gallon of water in the tank.
  3. Areas to be sprayed:
    1. The front yard east of driveway + east side yard to fat-pine pile + back yard = 24,000 SF
    2. The portion of the barnyard with the purple broadleaf = 2000 SF
    3. Total = 26,000 SF
    4. See Results below for an additional area that was sprayed.
  4. 26,000 SF will take 26 x 0.375 [3/8] gallons = 9.75 gallons of mix. Therefore, fill the tank with 9.75 gallons of water and add 9.75 x 1.25 oz = 12.2 oz. of WFZ. [NOTE – This calculation was wrong and made a very weak solution as it should have required the amount of WFZ to be 26 KSF x 1.25 oz/1000sf rather than 9.75 x 1.25. But, it worked at essentially 1/3 of the upper level of dosage.]
  5. Those amounts allow for no excess overlap or error in computing the area to be treated. Those issues could amount to 10%. To allow for that increase the water quantity to 10.5 gallons and the WFZ to 13.4 oz.


It was a perfect morning with no wind and sunny. The grass was mowed the day before yesterday. The sprayer has a more defined edge on the driver’s right side so went past the beds always on the right side. Kept about 3-4 feet between wheel prints in the grass. The mix with the 10% contingency covered all the areas in the yard other than the area between the drive path along the south side of the grain bin to the fat-pine pile. That area did not get sprayed.

An additional area sprayed one round was from the driveway to the pond along the rail fence south of the fruit trees. There is a lot of purple prostrate weeds and other junk that will hopefully be eliminated.

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