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Corn+Soybean Digest

Nitrogen's Kick On Corn

They don't claim to have the inside scoop when it comes to predicting fertilizer costs. But, with nitrogen (N) prices at all-time highs, some enterprising grain producers, along with the Iowa Soybean Association (ISA), had the foresight three years ago to begin evaluating application rates.

The group, the Iowa On-Farm Nitrogen Network (IOFNN), has conducted hundreds of strip trials on different farms with varying soil types, tillage systems and rainfall conditions throughout the state.

Its mission has been to examine and critique N application rates, then share that information to promote better land stewardship and control out-of-pocket fertilizer costs.

So far, the group's conclusions have challenged many to rethink what it means to develop and follow a plan that focuses on Nitrogen Best Management Practices.

Ray Gaesser, a no-till corn and soybean grower from Corning, IA, has been working with the Iowa On-Farm Nitrogen Network since its beginning. He's quick to say that one size doesn't fit all when it comes to determining N application rates.

"Perhaps one of the more striking things we've learned is that our best soils seem to need less nitrogen," says Gaesser. "We plan to continue to keep close tabs on nitrogen applications and yields because this conclusion contrasts with what the normal yield goal formulas suggest."

With his farm consisting mostly of loam soils, Gaesser has set up numerous test strips, each measuring about a half-mile long. He tries to use test strips that represent at least three different soil types and evaluates fall vs. spring application.

"We've looked at a standard rate of 160 lbs. N/acre, a medium rate of about 135 lbs./acre and a low rate at 90 lbs. N," he says.

Gaesser adds that soil samples are taken on each cropland acre at least every third year. He also uses corn nitrate stalk tests in early fall before harvesttime to track how well he's determining N application rates.

Based on results so far, Gaesser has confidently backed down on N rates. "Essentially, I've cut rates by 30 lbs., which has reduced my out-of-pocket costs by about $6/acre," he says.

Using a medium rate of 135 lbs. N/acre works well on his farm. On occasion, he also buys manure from a local poultry and hog farm.

"Producers need to examine their fertilizer application rates more closely, as well as when applications are made," says Gaesser. "We have a responsibility to make sure we're not overapplying nitrogen and to make sure we're applying it at the right time to reduce leaching."

Soybean checkoff dollars fund the network and encourage producers to participate, says Tracy Blackmer, director of research at ISA. "As an added incentive to join and help ease any reservations about risks of yield losses, the Iowa Department of Agriculture and Land Stewardship has set aside funds to underwrite any losses if they do occur," he says.

But the most meaningful aspects of the network center are being able to objectively examine and evaluate what works and what doesn't work in terms of fertilizer rates and timing of applications, adds Blackmer.

"We believe there's a strong profit potential in helping producers develop more site-specific fertilizer recommendations," he says. "That can be achieved by evaluating what's happening in their fields and making necessary adjustments."

Since its inception, the IOFNN has changed how producers determine N rates, adds Blackmer. Of the producers participating, slightly more than two-thirds have trusted their own trial results, shared and evaluated information with others, and ultimately scaled back on N rates at substantial savings.

"In just nitrogen alone, we've had a number of growers who saved more than $10,000 a year -- some have hit as high as $15,000-20,000 in savings, depending on the number of acres farmed," he says.

In the past three years, Blackmer says a few generalizations have surfaced based on observations and data collected by participants. Some of those include:

  • Overall, the majority of growers were already following the latest recommended N application rates and, in some cases, even applying less. By optimizing their management practices to more closely match their operations and conditions, many could safely reduce application rates even further.

  • Applying N in spring, especially close to planting time, requires lower rates and results in lower losses. This premise also applies to manure applications.

  • No-till systems require slightly more N initially if you're switching from conventional methods. N tends to be immobilized due to the higher carbon levels in the soil.

  • Significant losses of liquid N occurred if material was applied within 24 hours of rain.

  • It's important to calculate and account for manure credits, as well as factor in the carbon-to-nitrogen ratio. Those amounts should be fine-tuned by sample tests. Not all N in hog or other livestock manure is available the first year, according to the network's results. Incorporating the manure into the soil soon after application (or knifing in liquid slurry) greatly reduces N losses.

  • In side-by-side comparisons of using a 75-lb. N/acre rate vs. a 125-lb. N rate, no substantial differences in yield were identified. What little difference occurred in yield loss was easily compensated for by lower fertilizer costs.

"Showing someone how they can improve and backing that up with proven results can be a powerful way to make a positive impact," says Blackmer.

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