Developments in precision agriculture technology equipment make it possible to apply production inputs in variable rates across farm fields. The idea behind using variable rate technology (VRT) is that most fields are not homogenous with respect to yield-limiting variables. Therefore, some efficiency can be gained and profits increased by managing resources within the field to optimize output.

But an ag retailer offering services related to field mapping and prescriptions should not plow ahead with running up costs to the few clients with a field or two that do not justify varying prescription or variable rate application of inputs.
 
There must be some basis for varying the rate of inputs across a field. This has to be based on some type of field map that identifies different areas or management zones. As noted by Louisiana State University Extension personnel, “Currently, evolving technology is improving the possibility of basing variable rate applications on sensor-based, ‘on-the-go’ data.”

“Regardless of how the (field) map is developed, the idea is to identify areas within a field that have similar levels of yield-limiting variables. Once identified, these areas can be treated differently using variable rate application technology. The varying levels of inputs for areas within the field are defined in the prescription for the field... In theory, production inputs are applied in each area in such a manner as to maximize profits for that area. In doing so, profit for the whole field is also maximized,” the Extension specialist explained.

“Should site specific management and variable rate applications be used? One key to answering this question is identifying the amount of variability in a yield-limiting variable within a field. If there is little variability, site specific management will yield the same results as whole field management. Since whole field management is less costly to implement, it would be most profitable. The key question then is how much variability is required to justify implementing variable rate application?” the LSU specialists went on to point out.

Money is the main consideration of any farmer, the Extension specialists suggest. “Profitability is determined by the potential to modify input use among management zones in such a way that yield is increased and/or the level of input use is reduced. The magnitude of these changes must be sufficient to cover the costs of implementing variable rate application technology. Therefore, not only is the change in yield and/or level of input use important, but the price of the crop also enters the equation.”

Most fields vary in many ways across them, but having a farmer pay for something that doesn’t return on the investment is quickly spread mouth to mouth and can hurt the reputation of an ag retailer or crop consultant. It is just one small consideration but still a needed consideration.