Eric Wappel knows what prescription agriculture can do for their farm. He can list various components that make it up. He just can't put a definition on it. Neither could anyone in the audience at the Indiana Farm Management Tour when it stopped at their farm in Starke County recently. Eric farms with his dad, Larry, and his brother, Larry, Jr. and mother, Debbie.
Since precision farming arrived on the scene nearly two decades ago, ag economists have struggled to define it as well. They've also struggled to show payback. However, Wappel is convinced that it's earning its keep on their farm. One thing that makes it especially applicable for them is that they have a wide diversity of soils, from sands to mucks, and about everything in between, he notes.
"We use variable rate application to spread phosphorus, potassium and ag lime," he notes. "What we put where depends upon soil sample results. Soil sampling comes first. We use hybrids, but also factor in soil types and yield goals when deciding how much to apply where."
Rates for lime, for example, vary from a half-ton per acre to 2.5 tons per acre, largely due to variations in soils. "If we just applied two tons on the whole field, we would be overapplying lime on half of a field like that," Eric explains. By putting inputs where they're needed most, he believes they get their highest yields.
Variable-rate application also comes into play when applying nitrogen for corn, Wappel notes. He prepares many of his own prescriptions. Once prepared, they instruct the computer controller on board the tractor cab which rate to apply where. Here's an example of how they use variable-rate applications to vary N rates.
"We might average 150 pounds of N per acre," he explains. "But rates applied may vary from 100 to 200 pounds per acre."
For example, on sands, Wappel will likely build a prescription that applies about 125 pounds per acre. In muck ground, it may drop to 110 pounds per acre. On what they consider good, productive ground, he may instruct the computer to apply 165 pounds per acre. Under irrigation the rate may drop to 100 pounds per acre. "That's because we come back and apply N as we irrigate later as well," he notes.
Varying seeding rate for corn is one of the most important things they do, thanks to the variation in their soil types, Wappel says. He writes prescriptions that vary from 20,000 to 35,000 seeds per acre for the same hybrid
"If there's a sand hill in the field, we want to drop about 20,000 there," he notes. Average ground typically gets 31,000 seeds per acre. Since it's cool and wet and hard to get a stand in muck, the rate there might be 35,000 seeds per acre. On what we call good ground, we're typically going to about 34,000 seeds per acre."
Irrigated ground under center pivots typically commands 35,000 seeds per acre, he adds. "Before we started adjusting seed by variable rate application, we would likely have dropped about 31,000 seeds per acre, going for the average ground," he notes. "In that case the sand hills would likely dry up because corn was too thick. Meanwhile, we wouldn't get top yields in our irrigated acres because it can support higher populations. This way every acre gets what it needs."