Determining Sprayed Width for L/ha Applications

Single-Spot-Sprayers

Determining sprayed width for L/ha applications. Measuring the actual sprayed width in the field, under operating conditions, is critical to determining the application rate when a spot-spraying rate is not included on the product label.

WSP cards are useful for assessing the sprayed width. Once this has been determined, the following formula can be used to determine the application rate (L/ha):

L/ha = litres per minute per nozzle x 600 ÷ speed (km/h) ÷ width (m)

While WSP is a useful tool for determining where the droplets are landing, it will not indicate how many droplets will actually stay on the target weeds. When using high-speed, coarse droplets, there will be a lot of droplet bounce and shatter from the leaf surface, which may not be picked up when using WSP.

To assess actual spray deposits, it may be useful to consider using a fluorescent dye and black light blue (UV) torch to assess how much product is actually depositing on the target weed, and where on the weed the droplets are landing.

We have developed our own App to help with the calculations. Single-Spot-Spray Calculator.