Nitrogen loss through denitrification, leaching or volatilization can add up under common Midwestern growing conditions. In field trials conducted at Iowa State University and the University of Nebraska, researchers recorded the following sobering effects:
- Up to 5 percent of nitrate was lost per day through nitrification in wet soils with V1 to V3 corn.
- Nitrogen losses were as great as 70 pounds per acre due to denitrification on heavy ground when saturated soils received a simulated three-day rain event.
- On light-textured soils, nearly all applied nitrogen was lost under extremely wet conditions.
- Around 25 percent nitrate loss occurred when soil temperatures were 55 to 60 degrees Fahrenheit and fields were saturated for up to 10 days. Losses increased as soil temperature increased.
The 2018 growing season presented many of these challenges with damp, cold conditions, says Usher. “The extremely wet spring weather in some areas delayed planting and increased nitrogen losses in many fields. Where fertilizer was surface-applied before planting without a stabilizer, nitrogen losses due to volatilization may have been up to 30 percent.”
Without adequate levels of available nitrogen, crops tend to emerge slowly and unevenly, he says, “and that could cost five to 10 bushels per acre. It means the plant has to work twice as hard from the V4 stage and beyond, which is harder when temperatures get really warm.”
Andrew Usher takes a closer look at nitrogen application patterns.
Increasing N Availability
Nitrogen efficiency products are an effective tool for protecting a grower’s nitrogen investment. “Denitrification inhibitors and urease inhibitors help reduce nutrient losses to the environment and increase nitrogen availability to the crop,” notes Usher.
This season CHS Agronomy has added N-Edge® 2 nitrogen stabilizer to its line of nitrogen efficiency products. With the same proven urease inhibitor (NBPT) as the original N-Edge, the new formulation contains more active ingredients, making it more cost-effective per ton while providing a wider window of protection.
“The new formulation also contains a superior solvent system to reduce blending and drying times,” says Usher. Both N-Edge products can be used to treat urea or UAN and provide up to 21 days of protection from volatilization.
“With today’s tight crop margins, growers are scrutinizing every input dollar. A $2- to $3-per-acre investment in a nitrogen stabilizer will protect against nitrogen losses of up to 30 percent, like we saw last season,” he says. “That makes it worthwhile to use on every nitrogen ton.”
LEARN MORE: Visit chsn-edge.com.
FORMS OF NITROGEN LOSS
- Applied nitrogen is lost as ammonia (NH3)
- Air temp is high
- Soil is moist
- Urease activity increases
Volatilization depends on time and method of application. Surface applications of urea and UAN are prone to volatilization.
- Loss of nitrate as it moves with water past the root zone
- Higher frequency of loss in soils with low holding capacity
Leaching is greatest in humid environments, in highly permeable soils and in soils with tile drainage.
- Loss of nitrogen sources due to runoff
- Often negated by application, incorporation and field work processes
- Tie-up due to slow decomposition processes, microbe nitrate use and ammonia forms
Immobilization is greater (about 20–40 percent) in high-residue environments, but less in conventional tillage and corn-soybean rotation systems (about 10 percent).
- Loss of nitrate when soils are saturated
- Soils are warm
- Nitrosomonas are actively oxidizing ammonia into nitrate
Denitrification is greatest in poorly drained soils, but only when soils are warm.
Farm Bill Supports Nutrient Stewardship
Some state organizations have proposed restrictions on crop nutrient use. Leadership efforts within the U.S. Department of Agriculture and state departments of agriculture, combined with advocacy activities by industry groups including The Fertilizer Institute (TFI), have encouraged farmers to implement voluntary changes to crop management strategies and nutrient use.
“We’re seeing the needle move from early adopters to more broad-scale use of conservation practices and TFI’s 4R program,” says Jake Hamlin, director of state government affairs, CHS Government Affairs. “Many growers are implementing farm-specific practices like conservation tillage, cover crops and water retention to preserve air and water quality. Nutrient stewardship has become an integral part of conservation programs.”
He says those shifts are evident in the 2018 Farm Bill, which supports them in several key ways:
Priority on research — The bill increases support for university research and extension education surrounding 4R nutrient management promoted by TFI: using the right fertilizer
source, applied at the right rate, at the right time and in the right place.
Technical assistance — The new bill outlines a framework for providing technical assistance to help farmers adopt 4R practices to fit their operations, as well as third-party certification that involves cooperatives, other ag retailers and nonprofit organizations.
Innovation grants — The new bill provides $25 million in funding for conservation innovation grants, plus support of the Regional Conservation Partnership Program, which
includes the Environmental Quality Incentives Program (EQIP).
Follow-up data — Collecting information on the results of these activities will help identify best practices and guide future programs and funding.
Check out the full C magazine with this article and more.