Split Nitrogen Application: Where The 4Rs Get Real
When Illinois Grower Jeremy Wilson hit the farm conference circuit these past two years, one of his talks was always packed out — the story of his intense nitrogen management approach. His opening statement declared, “If you’re not applying nitrogen three times a year, you need to re-think your nitrogen plan.”
While many may view such a program as extreme, the current value of and methods for split application deserve a look.
Estimates on just how much split application is being done in the U.S. — and where — vary. John Larkin, Marketing Manager with 360 Yield Center, would put the number of growers doing split application at 30%, plus or minus 10%.
Use of in-season applications has been a common practice in the humid regions of the U.S. — and is becoming even more prevalent — especially along the East Coast, notes Dr. Harold van Es, Professor at Cornell University and lead inventor of the Adapt-N nitrogen modeling program. Environmentally sensitive areas like the Delmarva Peninsula have long committed to spring and in-season application.
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In Illinois, Jean Payne and Dan Schaefer of the Illinois Fertilizer and Chemical Association (IFCA) say splitting nitrogen applications started in the late 2000’s with improvements in application equipment. Then too, farmers who experimented with it saw benefits in being able to apply nitrogen in ways that improved utilization.
Payne and Schaefer say that in the last five years, the movement has accelerated with nearly all fertilizer retailers being able to service a split application program for all forms if nitrogen: ammonia, UAN and urea.
Wilson, who is also a Technology Specialist at Crop IMS, is somewhat skeptical. He believes adoption is limited and estimates that 75% to 80% of nitrogen is still being placed using just one pass, whether it’s a fall application, early preplant or a sidedress.
Towards Big Sky country and the Dakotas, Brent Wiesenburger, Precision Ag Manager at South Dakota Wheat Growers, Aberdeen, SD, reports that about 20% of his company’s corn acres are getting split applications of nitrogen.
“We are very dependent on rainfall in the Dakotas and tend to dry out very quickly. A split application allows a grower and agronomist to analyze the crop yield potential and make incremental investments in nitrogen if it looks like it is going to be a good year,” he says. In dry years, growers don’t spend the extra money on that second or third pass of nitrogen. In many cases, Wheat Growers will blend ammonium sulfate in on the second or third pass as well, as they are both mobile nutrients.
In Kansas, Nathan Woydziak, Precision Ag Manager at Crop Quest Inc., says uniform split applications have been used for decades there. In wheat, for example, part of the nitrogen needed is applied in the fall, then another is considered in spring, depending on environmental and crop conditions.
In irrigated crops, the concept is “pretty simple” to implement, Woydziak says, with the first dose of N applied in fall or early spring (often done variable rate), then the rest is “spoon fed” through the pivot as the crop progresses through the season. Split application has been embraced as a good management practice. And it’s especially important in sandy areas where N leaches more easily through the soil profile.
Benefits In Brief
The main benefit of split application is that it provides much higher nitrogen use efficiency, plus the ability to prevent nitrogen losses in wet springs. Farmers save money and greatly reduce environmental losses, especially when they add the use of a good weather-based nitrogen advisor or nitrogen model, says Cornell’s van Es.
Sometimes it takes a shake-up to prove a practice and increase adoption. Yield 360’s Larkin describes how in the summer of 2015, much of the Corn Belt had heavy rain events that flushed nitrates out of the root zone. Late season rescue applications of nitrogen had a dramatic impact on yield.
“Then in 2016, which was an ideal growing season in many areas, and we saw heavy mineralization — so nitrogen was rarely a limiting factor in yield. But those growers who had adapted a split N program the previous year had the flexibility to reduce their last N application rate and pocket input cost savings while maintaining the yield potential,” Larkin explains.
This ability to stay nimble and flexible and react to the seasonal variation in N availability has helped growers understand the profit potential in mid-season application, he emphasizes.
Challenges To Widespread Use
Experts listed a number of roadblocks that stand in the way of wider adoption of split programs:
Resources. Additional applications, especially late season work, take additional equipment, manpower and time.
Convenience. Quite simply, fall is when there’s time to get the chore of fertilizer application completed and crossed off the to-do list.
“It is also risky to have a deficient crop standing out there knowing a grower’s application window is quickly disappearing in late June to early July as the crop is growing very rapidly,” says Wheat Grower’s Wiesenburger.
Then too, the actual speed of different equipment used for additional applications varies. Wilson points out that applicator operators just can’t get over the same number of acres with a rig sporting a coulter bar injecting fertilizer as they can with a high-clearance spreader applying urea.
Weather. Will weather conditions permit getting back into fields later? If a grower holds back nitrogen until post planting and then it rains, there is a risk they miss the application window and run out of nitrogen — or they need to bring a plane in to fly expensive urea on the field, says Yield 360’s Larkin.
He would add: “That’s one of the advantages of the Y-Drop system: by extending the window to V11 or even VT, there is a very wide window and little risk of missing out,” he adds.
Yield 360’s Y-Drop tool, attached to spray booms, drizzles nitrogen at the base of the stalk. “In fact, we hear people talking about ‘Y-Drop season’ now, meaning a mid or late season application using the Y-Drop system. That certainly didn’t exist three years ago,” Larkin notes. Yield 360 also offers Y-Drops that mount on an applicator bar for sidedressing.
Cost. Growers perceive — and it’s sometimes true — that anhydrous is the cheapest form of nitrogen and is relatively stable.
Supply and Demand. Fertilizer is a commodity, and price fluctuations can influence nutrient decision-making, say IFCA’s Payne and Schaefer. It can either delay application or tempt a grower to want to apply a product (either N, P or K) to take advantage of a price shift in the nutrient cost. The price difference between ammonia versus UAN or urea can also influence an application decision.
Clients. Retailers have to determine which customers might be open to multiple applications. “If you have growers who are pushing that nitrogen application to the max in an early application, they are probably not the guys to talk to,” Wilson says.
Instead, pick growers who are doing some of their applications themselves. They’re set up to do their first two passes, they have all their own equipment to do an early preplant or even a fall application. “I think an area where they can do fall anhydrous — like central and northern Illinois — is even better.” Wilson would recommend these growers pull back on fall work, with the thought of potentially putting on two applications in season.
“Also look at producers that are running on the lighter side of what you believe is enough to grow the kind of corn they want to grow. I think the likelihood of success is probably much higher there,” he adds.
This practice is not for everyone, Wilson stresses. “The return has to be positive to the grower or it’s ridiculous to even talk about it.”
Mapping Soil Variability
Experts say another roadblock to wider use is identifying where and when split applications — uniform or variable rate in-season — bring benefit. That’s where soil mapping that pinpoints field variability plays such a crucial role. And while there is some debate on zone versus grid approaches, the goal is to organize as much georeferenced data as possible.
A wide array of tools are available for the job, but some of the most cutting edge have been Veris Technologies’ on-the-go sensors. The probes measure pH, organic matter and electrical conductivity (the last two being indicators of soil texture and water and nutrient holding capacity).
Just in February, Veris introduced the iScan, an implement-mounted soil sensor. In the past, the company’s sensors made independent passes across the field. With the iScan, users can mount them on tillage tools on planters for real-time data collection. “It’s easier, less expensive, and there’s less input required to collect the data,” says Tyler Lund, director of sales and marketing.
“Growers know they have a little bit of variability in their fields, they don’t understand just how different the soils can be,” he says. “When they’re actually involved in the data collection process because the sensor is mounted to the tool, tillage or planter, they’re going to be confronted with a real-time display of that map. So they’ll see those patterns emerge. Once you’re eyes are opened to the level of differences in your field, you don’t want to go back to managing it as if it was one type of soil.”
Enter split applications. “The reason we don’t want to apply nitrogen all at once is we know we can lose it, and our level of loss throughout the field is different,” says Lund.
To help more growers understand the variability of their soils better, Agronomic Technology Corp. recently introduced N-Insight, an instant nitrogen diagnostic that is simple enough for producers to deploy on their own in every field or subfield. It’s based on the same platform that produces Adapt-N, which is known for its industry-leading nitrogen modeling validation, says Steve Sibulkin, company CEO.
“It’s a ‘conversation starter’ that quantifies a grower’s nitrogen loss in each of the past five years and allows him to get a real sense of likely outcomes due to changes in timing, rate and nitrogen source,” says Sibulkin. He explains that retail and coop agronomists use N-Insight to help growers understand the value of split application, the need for nitrogen stabilizers, and more.
What about doing variable rate applications in-season? Wheat Growers’ Wiesenburger say his team is not doing them yet as part of its zone management program (MZB). “We simply give growers credit for X pounds of in-season nitrogen and remove that amount from our variable rate application. This makes the approach more operationally friendly in crunch time in season — and it’s also well received.
Wheat Growers has been looking at in-season nitrogen management tools to help staff variable-apply and make decisions on the fly, but the firm has struggled operationally to get tissue sampling done, manage in-season satellite images, etc.
Dr. John Fulton, Associate Professor at The Ohio State University, does note that imagery is becoming cheaper and more accessible to growers and their agronomists. It can reveal crop vigor and health variability — leading to opportunities to vary N rates in-season, especially later in the season. He could easily see growers making three or even four N applications to a corn crop, though not every year.
“Variable-rate applying nitrogen based on imagery can work well, but in our area it requires some investigative work, says Crop Quest’s Woydziak. “We have to be confident that what the image is showing us aligns with what the boots on the ground tell us.”
Crop Quest agronomists perform regular field checks to ensure what they are seeing in the images matches what they see on farms. When the two agree, then imagery can be used in-season to address problems.
“Again, all of this will get better and easier with time and technology, it is just a matter of getting our feet wet and understanding the challenges and adapting as we go. Five to eight years from now I believe VR in-season application will be standard practice and become something we just plan to do,” says Wheat Growers’ Wiesenburger.