When farmer Brad Tinsley ventured into precision agriculture 16 years ago, he wasn’t sure where the new technology would take him. Today a goal has come into focus – to get the most from every acre with a variable-rate approach for fertilizer, lime, nitrogen and seed.

Tinsley farms corn, soybeans and wheat near Mercer, Tenn., often sharing equipment and labor with neighbors Ken and Joe Couch.

Tinsley dropped cotton from the mix this year based on economics, but labor, time and stress were also factors. “Last fall, I was trying to run a grain crew and a cotton crew and was pulled in so many different directions to get planted. I’ve always liked cotton, but it was just one of those things where I wanted to take a break from it, to see what would happen. I don’t think I’m going to be completely out of it. If it hits a dollar a pound, everybody will be thinking about it again.”

Tinsley has been steadily trimming his cotton acres over the past few years anyway and was down to 200 acres. The decision to sell his cotton picker made the shift out of cotton all the more reasonable.

Tinsley’s venture into variable-rate applications for cotton and corn began in 1997 with the help of Mid-South Farmers Cooperative – Precision Ag Services, which was moving aggressively toward precision farming techniques at the time. “We started sampling on 2.5-acre grids. In the beginning, it was all about lime. In my opinion, that’s where you’re going to see the biggest benefit. From there, we went to variable-rate phosphate and potash."

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Today, Tinsley has been experimenting with variable-rate seeding for corn for two years and likes what he sees so far. It’s been a work in progress, however.

“We are still learning. When we first tried it, it didn’t work like we wanted it to. We were doing prescriptions off soil samples, and I just didn’t feel comfortable with it. I would be in the cab, and the seeding rate just wouldn’t feel right, so I would dial it back manually.”

Last year, Tinsley teamed up with Alamo, Tenn., precision ag consultant Jonathon Poston to write variable-rate prescriptions based on yield history, and things started to fall in place for Tinsley. “It may be different for other farmers, but in my opinion, yield history was the way to do it.”

“We variable-rate planted our corn anywhere from 34,000 plants in the high zones down to about 26,000 in the low zones,” Tinsley said. “This year, we should’ve bumped it up a little bit. First of all, we didn’t get a good stand planting in the mud. That hurt us. We should have had 1,000 to 2,000 more seed per acre in each zone.”

Tinsley stresses that yield history can be ambiguous. “You have to be picky about the data. I can use soybean and cotton history for corn variable-rate seeding prescriptions, but I can’t use wheat history. And I have to pick good years out of the data.”

Knowledge of the field is essential to this process, Tinsley noted. For example, “you may recognize that a low-yielding part of a field had flooded out. So you have to go in there and tweak things.”

Tinsley and Poston usually write variable-rate prescriptions for three management zones. “If you use too many zones, it starts getting too complicated,” Tinsley said.

Although Tinsley prefers to base prescriptions for corn seeding off yield data, he continues to write fertilizer and lime prescriptions from soil data. Four years ago, Mid-South Farmers Cooperative ran an electrical conductivity mapping cart, or Veris rig, which maps soil type, over Tinsley’s farm.

“I was trying to get away from grid-sampling because it was so labor-intensive.” Tinsley said. After the soil type is mapped by the Veris rig, soil samples are pulled from various zones to guide a variable-rate prescription. “We may pull three samples from each zone. It’s a whole lot easier than pulling samples on 2.5 acre grids. That’s I hired-out job. We spent all winter doing that one year.”

Tinsley is considering going to variable-rate seeding in soybeans in 2014, “But we still need to do some research on it. With corn, it’s obvious you want to put the higher population on the stronger ground, but on soybeans, we don’t know yet. They can get rank and lodge on you.”

Tinsley plants with a Case IH 1240 and a John Deere 1720, both of which are equipped with variable-rate seeding capability.

Tinsley relies on automatic guidance for most of his field operations. Tennessee Tractor and the Tennessee Department of Transportation have base stations available with RTK accuracy with a subscription.

Tinsley has found RTK to be essential. “Number one you can take your hands off the steering wheel and eat lunch. But seriously, if you can hold that header within 6 inches every round, look how much you’re saving at the end of the day. With the way fuel costs are these days, you have to make you have to make every gallon count.”

Tinsley also variably applies his nitrogen on corn with a Schaben liquid application rig. Nitrogen rates range from 165 units to 230 units.

This spring, Tinsley applied variable-rate nitrogen on wheat using In-Time infrared imagery. The precision farming service provider based in Cleveland, Miss., flew the field before the second application of nitrogen. “It looks like that is going to work pretty well. I was impressed with it.”

Tinsley doesn’t believe that variable-rate applications have necessarily saved him money on fertilizer or nitrogen. But crop yields are higher and more consistent.

“When this variable-rate technology started, everybody was thinking they were going to save so much money on fertilizer. I don’t think that’s the case, but you are putting it where you need it.”                                                                                                                                                         Ag news delivered daily to your inbox: Subscribe to Delta Farm Press Daily.

The same holds true for seed, said Tinsley, who is 100 percent dryland. “In all honesty, with all the acres of corn I have, I would have used the same amount of seed whether I was variable-rate or a straight rate. But I did get my seed where I wanted it.”

Variable-rate application is about trusting the technology for Tinsley. “When we started doing variable-rate, we were scared to death. What if the truck didn’t put it out right or what if it wasn’t applied in the right spot? But over all these years, if anything, our soil fertility has gotten better, so I know that it’s working.”

But most importantly, variable-rate applications are about getting the most from each acre, Tinsley said. “I’m trying to squeeze it for what it’s worth. I’m always trying to improve and make sure that every input has a return.”