In the 1990s, Arkansas producer Marty White first tried variable rate fertility. At that time, some of his landowners were precision leveling several fields, and White wanted to make sure his fresh-cut fields would be brought up to production.

“We worked with Art Simpson, who managed the Marked Tree Co-Op in Marked Tree, Ark.,” says White, who farms near Weona. “He helped pioneer variable rate technology (VRT) in our area. Today’s VRT technology and equipment is much more sophisticated than what we first worked with.”

White’s interest in variable rate fertility increased a couple of years ago when fertilizer prices soared. “At that time, fertilizer prices spiked, and potash and phosphate cost $800 to $900 per ton,” he says. “Since fertilizer was so costly, I wanted to make sure we were applying it where we needed it. Today, Taylor and Stuckey, located in McCormick, Ark., applies the majority of our fertilizer, and Ritter Crop Services in Marked Tree does the rest of it.”

Fertilizes for higher yields

Consultant-Designed Program

Marty White now works with Field Concepts, a division of Strike Zone Ag, for his variable rate technology. Field Concepts is a consultant-designed program that provides site-specific grid sampling and variable rate prescriptions for dealers, consultants and growers. Field Concepts’ benefits include expertise on software and equipment purchases; customizable equation writing; support in equipment and software set-up; and fast, reliable in-field tech support. “My consultants, Eddy Cates and Lance Ramthun, pull our 2 1/2-acre grid samples,” White says. “We send the samples to the University of Arkansas, and they send us the results. Field Concepts handles it from there, providing variable rate prescriptions and other services. Their people are great to work with. They give us all the tech support that we need and basically take care of everything.” For more information about Field Concepts, call (877) 336-8262 or go to www.strikezoneag.com.

White has always fertilized heavily for higher yields. He says using variable rate fertilizer enables him to apply potassium and phosphorus more efficiently. “We’re probably putting out close to the same amount of fertilizer that we used to put out in a blanket application, but we’re now putting it precisely where it’s needed,” he says. “On some fields we’re putting out more fertilizer than we formerly did, and, on other fields, we’re putting out less and sometimes none in some parts of the field.

“Variable rate fertility really pays off in fresh-cut fields that have some spots where so much dirt had been moved that they’re underperforming. However, even on ground that is not fresh-cut, we still have weak spots that we notice every year and wonder what’s wrong. It’s usually due to inadequate fertilizer levels. Instead of needing 100 pounds of potash per acre, that particular spot might need 200 pounds; it just hasn’t been getting the right amount even though we’ve been fertilizing it. Variable rate fertility remedies this problem.”

Grid samples all fields
This Arkansas grower now has his entire acreage grid sampled on 2 1/2-acre increments. He started with his fresh-cut fields and then began sampling his other fields. The grid samples are good for three years. “The benefits of variable rate fertility are great for soybeans and my other crops,” says White, whose two sons, Jesse Flye and Logan White, have worked full-time with him since they were 18 years old. “We do it for all of our crops – soybeans, rice, cotton, corn and wheat.

“For example, we see more uniform growth across the field with variable rate; you can really see the difference in some fields. On our fresh-cut fields, we’ve maintained our prior yields, and every year we work this program our yields are increasing.”

White also variable rates his lime. “That is where the program really pays off because lime is so expensive and only parts of my fields really need it,” he says. “We irrigate so much – about 90 percent – that I don’t have a whole lot of lime issues; the deficiencies are only on my pivot corners and a few dryland fields. Our irrigation water keeps the pH more level than the dryland corners. A colored soil map of a pivot-irrigated field vividly shows that all four corners often will call for lime while the circle won’t.

“We mainly lime our non-irrigated fields and pivot corners. The savings alone on lime pays for the program. Lime costs $20 to $25 per ton, so if you’re putting out two tons per acre on an 80-acre field, that totals160 tons. With variable rate, you might only need 40 tons, and that’s a huge savings.”

Field Concepts contributed information for this article.