The discussion we've heard this winter is split on whether variable-rate seeding for corn pays. Some farmers say it does. Others say they just spend more on seed and don't see a yield increase. Some have stopped doing it. Others who have the precision equipment in place continue to try it.
Bob Nielsen, Purdue University Extension specialist, believes it pays primarily only if you have two soil types in the same field, and one soil type has a true cap on yield. Maybe it's sand or maybe it has an extremely low cation exchange capacity. If the best it can do is 130 bushels per acre in a good year, he suggests capping it at 25,000 seeds per acre as a goal and seeding the rest at 32,000. Otherwise, his data so far indicates that 32,000 is about as high as anyone needs to go on seeding rate.
Some seed companies are showing different results. Several have tested their individual hybrids at different population levels, and will make that information available to customers.
For example, DuPont Pioneer recommends a four-step approach to determining if you want to vary rates when planting corn. The first step involves breaking the field into management zones. One of the other main steps involves studying the reasons of individual hybrids to different populations. Pioneer has a special tool on its Website that can help farmers gain information on how each of their corn products reacts to varying seeding rates.
It's called the planting rate estimator. You enter information about corn price and a few other variables, select the hybrid you're considering, and a graph pops up showing profitability at various seeding rates. For some hybrids the suggested seeding rate will be higher than for other hybrids. What you end up viewing is a yield curve for each product at different seeding rates. It could be extremely helpful in determining rate, and if you should use different rates based upon production potential.
You can find the tool by clicking here. It's worth the time it takes to get to the site.