Granule Distribution Uniformity

ABSTRACT AN index based on the average A squared shortest distance between random points and herbicide granules was used to quantify uniformity of herbicide granule distri-butions. The theoretical granule rate needed for control increased linearly with the distribution index. Control for a given granule rate increased, both theoretically and in greenhouse tests, with increase in distribution uniformity. Response of control to uniformity of granule distribution was greatest for the rate of herbicide that gave acceptable control evenly when granules were uniformly distributed. When herbicide rate was excessive, control was high and independent of uniformity. When herbicide rate was low, uniformity of application had very little effect on weed control. Theoretically, about two to four times as much herbicide must be applied with commercial granule applicators to obtain acceptable control as would be needed if granules were uniformly distributed.