Variable Rate Herbicide Application

It is well established that preemergence herbicide activity is influenced by soil type, and recommended rates for most soil-applied herbicides are adjusted to soil type. Current technology allows application rates to be adjusted on the go (VRA), adjusting the rate as soil type changes in a field. Most applicators offering this service base herbicide rates on soil organic matter content. However, several other factors influence herbicide activity, most importantly weed density and environment. This research is to determine which of these factors is most important in determining the optimum herbicide rate, and the economic benefit of VRA to the grower. The objective of this study is to determine the relative contribution of soil type, weed density and environmental factors on herbicide effectiveness.