Progressive Farmer — Mid-February 2016
New Days For Nitrogen
Darcy Maulsby, Contributor

Growers use in-season applications to maintain high yields and manage costs.

When Denny Friest started farming full-time in 1970, the rule of thumb for nitrogen (N) management was straightforward: Apply 1 to 1.5 pounds of N to produce a bushel of corn.

“N was relatively cheap then,” recalls Friest, who farms near Radcliffe, Iowa. “While soil testing was available, there really was no way to manage N very accurately.”

THAT WAS THEN. The days of treating N like an insurance policy are gone. Beyond the current commodity cost crunch, growers are under an environmental microscope. Providing just enough N and applying it just in time are the new realities they face, and N management has become a year-round concern.

Friest, who raises 1,400 acres of corn and soybeans with son, Brent, found help in negotiating the new realities from Iowa’s On-Farm Network. Formed in 2000 by the Iowa Soybean Association, it includes a team of specialists who partner with farmers across the state. Participants use precision agriculture tools and technology to discover, accurately validate and increase the use of the right combinations of inputs and practices that improve efficiency, profitability and environmental stewardship.

Friest’s first trials were a no-lose proposition. “I was asked to cut back by 50 pounds of N on three replicated strip trials in corn. If I lost yield, I’d be compensated for the financial hit,” he says. “In one year with a dry spring, I got down to 60 pounds of N and still harvested over 200 bushels per acre.”

Return on investment outranks yields though. “I’m willing to sacrifice some bushels if the cost of producing those extra few bushels is too high,” he adds.

Friest also knows it’s unrealistic to think all N can be managed perfectly. “We’ll never get down to zero nutrient loss. Still, we need to be involved with finding new ways to manage nutrients more efficiently,” he says.

“Growers are definitely paying more attention to N as they look for ways to maximize every input,” says Peter Bixel, team leader with MaxYield Cooperative’s SciMax Solutions, in northern Iowa.

SciMax Solutions uses advanced technology and local field trials to help growers with variable-rate nitrogen and other precision solutions. “While the old mindset was ‘more is better’ with N, we take a scientific approach to N management,” Bixel says, stressing the importance of starting with grid samples and determining where N is needed. “We’re finding that most of the time, we don’t need extra N,” he adds. “We just need to variable-rate the N.”

In 2015, one of Bixel’s own corn fields averaged 256 bushels per acre with 136 total pounds of N applied. This included 86 pounds of variable-rate, fall-applied anhydrous, 50 pounds of flat-rate, sidedress urea ammonium nitrate (UAN) and 15 pounds of N from a variable-rate MAP (11-52-0) fertilizer application.

“We’ve been able to reduce more than 30 pounds of N per acre, on average, for our SciMax clients,” Bixel says.

Mike Riggert, who farms with his brother, Brian, near Whittemore, Iowa, uses the SciMax program. They pull soil samples in the spring so the SciMax team can review the results and help them develop a nutrient plan for that crop year and those that follow.

TIMELY INVESTMENTS. Throughout the summer, the Riggerts scout their crops and work closely with the team to collect tissue samples, assess fertilizer options and pinpoint where nutrients should be placed for maximum returns. By early fall, the Riggerts work with SciMax on their variable-rate fertilizer, including variable-rate nitrogen plans, for the following year.

During spring 2015, rotated acres got a preemerge base rate of 65 pounds of UAN. Variable-rate sidedress applications averaged 60 pounds of UAN­—although there were some areas that got none. Corn-on-corn acres received a flat rate of 100 pounds of N applied preemerge with UAN, followed by a sidedress application of N that averaged 58 pounds per acre.

“We’re constantly thinking about ways we can do a better job of farming,” Riggert stresses. “A little effort can yield some big payoffs with long-term benefits. Our goal is to continually improve.”

Bixel has been impressed by corn growers’ increased willingness in the last few years to try split applications of nitrogen. “Whether this involves sidedressing, spreading urea with an airplane or having the co-op apply urea, growers are viewing this as a way to spread out their risk,” he says.

In 2015, Bixel worked with a north-central Iowa grower who spread variable-rate urea with Instinct N stabilizer before he planted his corn-on-corn acres. That application included 76 actual pounds of N, followed by 70 pounds of UAN 32% flat rate when the grower sidedressed his acres. Another 30 pounds of N came from MAP (11-52-0) that was variable-rate applied in the fall. “This grower had a field average of 229 bushels per acre for corn on corn,” Bixel says.

FREE FERTILITY. Hog manure is more than something to dispose of in the Friests’ fertility program. It is injected with a flow-control system, so a precise amount of gallons and nutrients are applied to 75% of their corn acres. A base rate of 3,000 to 3,500 gallons of hog manure is applied—the majority (90%) in the fall and the rest in the spring.

Nutrient analysis determines actual applications. Manure from finishing swine barns typically averages 50 pounds of N, 25 pounds of phosphorus and 30 pounds of potash per 1,000 gallons, Denny Friest says.

Anhydrous ammonia is applied in the spring to the remaining 25% of the acres. He uses a base rate of 80 to 100 pounds of N for corn following beans and approximately 130 pounds of N for corn following corn. “I look at split-N applications as a way to manage N loss,” says Friest, who reassesses his crop’s N needs in early June.

Friest farms in the Des Moines lobe, a region comprised of Clarion-Webster soils that tend to be poorly drained. Spring rainfall patterns and field ponding are indications of excessive rain and potential N losses. “If it has been dry, however, we probably won’t put on any extra N,” he says.

Friest used to sidedress after the corn was at the five-leaf stage. New technology in the form of 360 Y-Drop applicators now extends the application window. “With the Y Drop, I can apply 32% N from knee-high to tassel,” says Friest, who uses an OptRx crop sensor system from Ag Leader Technology. He adds, “How much N is applied depends on what my crop is telling me.”

Ward Van Dyke, Pella, Iowa, is also evaluating new N management tools. He farms 1,500 acres in the Skunk River Bottoms, where many of his fields contain heavy, black gumbo. For the past several years, he has applied 32% liquid N “weed and feed” with his herbicide before planting. On bottom ground, he follows with a sidedress application of 100 to 175 pounds of N at the V3 to V5 growth stage, depending on the crop’s needs. On hill ground, he uses N-Serve stabilizer when he fall-applies 150 to 160 pounds of anhydrous.

“I began splitting my N application because I want to feed the crop just in time when it needs N,” Van Dyke says. “While the higher rate of N has paid off for me most of the time, especially in wet years, you can’t generalize N management. As commodity prices drop, higher rates of N don’t always pay, and it may not make sense to get those last few bushels,” he continues.

SENSE AND SUPPLY. In recent years, new technologies have come to market to help growers better manage their N applications through weather extremes. Friest decided to invest in the OptRx crop-sensor system, which includes three different sensors mounted on his Hagie sprayer’s 90-foot boom. The sensors measure and record crop data in real time using the reflectance of light shined on the growing plants. The equipment also provides N-application rate recommendations.

“The technology assesses how green the crop is, which helps determine how much N to put on,” Friest explains. “While justifying the cost of this equipment is a challenge, the technology shows promising results and is another tool in our N-management toolbox.”

Farmers are becoming more sophisticated with N management, notes Peter Scharf, a professor in the division of plant sciences at the University of Missouri. “While they want N management to be fast, simple and affordable, they also want to deliver N to the crop when the crop needs it,” says Scharf, who is also a university Extension nutrient-management specialist. “The big change I’ve seen lately is farmers’ willingness to apply N in-season.”

This prompted Scharf to take years of university research and develop NVision Ag (, which helps farmers decide whether they need more N for their corn crop and determine where to apply N and how much. Launched in June 2015, NVision Ag uses aerial images and patented University of Missouri research to create yield-loss maps, total yield-loss estimates and N-rate control files. The system costs $2 per acre to acquire the aerial images, $4 per acre for the yield-loss map and $4 per acre for the nitrogen-rate control file.

APPEARANCE MATTERS. “The system determines how much variable-rate fertilizer to apply by the color of the corn,” explains Scharf, who works with farmers, ag cooperatives and crop consultants. “It’s the same principle as a crop sensor. Dark areas get a lower rate, while lighter areas get a higher rate.”

Missouri growers know exactly how wet spring conditions can be after the 2015 season. Scharf says one of the real strengths of the NVision program is helping determine how much N has been lost during excessive rainfall events. “For planned in-season N, we’re about as good as sensors,” Scharf says. “What we can do that they can’t is tell a farmer which fields need more N application when N loss conditions (lots of rain) occur.”

While NVision Ag teamed up with farmers in Missouri and Illinois in 2015, the company can work with growers throughout the Midwest and beyond, as long as there are enough acres in their area (typically 1,500) to justify sending a plane there. “From the air, an N deficiency sticks out like a sore thumb,” Scharf says. “It also sticks out on the yield monitor at harvest.”

FERTILITY PARTNERS. While N captures most of the spotlight when it comes to fertility, don’t forget other agronomic basics, like proper pH, soil testing and nutrient interactions. Those factors play a valuable role in crop development, as well.

“Potassium is closely connected to N,” Bixel says. He notes that potassium helps move N through plant roots.

“If potassium levels aren’t right, the plant can’t take up N efficiently.”

Hands-on nutrient-management practices also serve farmers well. Friest is considering using N-Serve stabilizer with his spring-applied anhydrous ammonia. He’s also experimenting with cover crops as he works with the On-Farm Network. “It can be challenging to get cover crops to grow after harvest in my area, but I’m interested in seeing if there’s a practical way to gain both environmental and economic benefits from them.”

Van Dyke is in his third year with cover crops, including cereal rye. Along with studying cover crops in 2016, he wants to compare anhydrous ammonia at sidedress to 32% N on his acres. In 2015, he compared sidedress anhydrous ammonia without N-Serve Stabilizer to anhydrous with N-Serve. The N-Serve delivered a 3.5-bushel yield bump.

“The more trials you do, the more you want keep testing and see what works best,” Van Dyke says. “I encourage every grower to get involved with something like the On-Farm Network and to learn what works for their farm.”

There is no one-size-fits-all when it comes to N management, adds Friest, who is excited about the new tools available for improved N management. “We’re always learning and considering both economics and environmental issues as we determine what makes sense for our acres.”

This focus on continuous improvement is smart management, especially when it comes to N management, Van Dyke says. “The drive to be more efficient keeps me motivated. I want to become a better steward of the land every year.”