So you have row clutches on your planter, and you are equipped with GPS and a computer system. You could vary the seeding rate of corn across the field. All you have to do is program in different rates for different locations in the field. There are plenty of people who can write prescriptions to do that, right?
"The question is: Should you vary rates just because you have the capability and can do it?" John McGuire says. He operates Simplified Technology Services based in Montpelier, Ohio.
He doesn't believe "just because you can" is good justification for using the hardware in that way. Instead he believes you need to apply what you learn from analyzing data to decide if varying rates is what you ought to do or not.
If you're out to vary rates of inputs, start with the ones that are simple and make sense, he says. Start with ones where the payoff can be measured and depending upon pH and soil test levels in your field, could be rather immediate. He says it makes sense to vary the rate of lime applications if you have good soil test data. Likewise, it also makes sense to vary the rate of phosphate and potash fertilizer if there are differences in recommendations across a field based on soil test results.
To know whether you should vary seeding rates, however, you need two pieces of information. You need to understand your soils and their yield potential, and you need to understand the hybrid that you have chosen for that field, McGuire says.
"The reason that you should use variable rate technology on any one input is because the data tells you it is the right thing to do," he concludes. "It has nothing to do with whether you have the capability to do it or not."