The herbicide is delivered in 40 pound bags that look like they might contain fertilizer. Although we are only putting a very little bit of chemical in the water, we want it to be absorbed at or near the roots of the plants so far as possible. So the chemical comes blended in pellets of chunks of clay, which will sink to the bottom before dissolving and releasing their active ingredient.
It is poured into hoppers on the back of the boat. Under each of these there is a powered spinning disk that spreads the pellets several yards either side of the boat. (click on the thumbnail to enlarge) The driver follows a programmed course that zigs and zags back and forth to cover the designated treatment area. And the speed of the boat and the hoppers’ flow rates are regulated to ensure that the herbicide is delivered at the desired concentration.