Just-In-Time Nitrogen

June 24, 2017 02:43 AM

Build your nitrogen inventory using the 4Rs

Nitrogen (N) application isn’t a once-a-year job. It’s about maximizing total input and output efficiencies, like an automobile assembly plant, describes Farm Journal Field Agronomist Ken Ferrie. 


“Each morning the facility gets in the exact number of parts needed to assemble the vehicles on the line that day,” Ferrie says. “After assembly, the vehicles are shipped out within a mere number of hours.”

The assembly process requires high-touch management and planning to ensure every step is in sync. The same can be said for your N program. 

“Don’t try to apply all of your N in the fall with the goal of making it until R5 in August,” Ferrie says. “Instead, think of your N program as ‘just-in-time inventory’ where your supply and demand are in sync.” 

The Farm Journal Test Plots program in central Illinois and southern Michigan has been focusing on making N available just in time and the 4Rs—right product, rate, timing and placement—of nutrient management.

Timing. The goal is to calculate daily N uptake need and match it to the growth stage. There are several computer modeling programs that provide this information, many of which are fairly accurate but still need to be ground-truthed before making management decisions, Ferrie says. 

What Ken Ferrie and Missy Bauer Think You Need to Know
  • Determine fields’ ability to supply N by testing for mineralizing N or planting N plots. 
  • Evaluate risk of N loss. If soil is well-drained, you risk leaching, if it’s poorly-drained you risk denitrification.
  • Pay attention to the environment, and be equipped to apply N via any method. 

To evaluate daily and cumulative N usage, the Illinois crew pulled soil tests to track nitrate movement, collected tissue samples, documented plant uptake and grew corn hydroponically. 

From emergence to V8, the plant consumes less than 2 lb. of N per acre per day. While N uptake is not much because plants are small, don’t underestimate this stage because it impacts overall yield potential, Ferrie notes. 

From V10 to V18, the plant consumes 5 lb. to 10 lb. of N per acre per day, known as the rapid vegetative growth stage. Once the plant has reached R1 and is pollinated, the daily usage backs off to about 2 lb. per day.

“When corn hits R1 and drops its daily usage to 2 lb. per day, you still have 60 days of this stage remaining,” Ferrie says. “It’s critical you meet the 2 lb. per day demand, whether you or the soil supplies N, to reach maximum yield potential.”

Knowing uptake needs dictates how aggressively you apply N based on growth stage, Ferrie says.  

For example, if you pull a nitrate sample on May 10 (growth stage matters more than date) and the results are in the medium to low range, you need to react immediately because N usage is about to increase during the rapid vegetative stage. However, if you pull the same sample on July 25, a medium to low reading is manageable because the plant only needs 2 lb. per day. 


Ultimately, the more N your soil supplies, the less you have to apply. Fields with low-supplying power are more likely to respond to multiple N applications, even later in the season. 

Before applying N late in the season, make sure the plant needs it. In 2015, central Illinois received 16" of rain in June. As a result, the later N applications (at tasseling) created large yield responses because the corn didn’t have enough N to finish the growing season. 

“This was not the case in 2016, an N-friendly year with moderate rainfall in central Illinois, as evident by consistent nitrate samples at 1' and 2' during the growing season,” Ferrie says. “You have to understand the risk of loss—just because the late-season application resulted in high yield responses in 2015 doesn’t mean you’ll get the same results the next year.” 

For example, in central Illinois, Ferrie and crew pulled regular nitrate samples starting Feb. 29. An N application was made prior to the fifth pull and the sample at 1' responded more than the 2' sample. For six weeks, a similar response was observed, which Ferrie says is positive because the applied N stayed in the upper 1' of the soil where it is most accessible. 

The week of June 13, heavy N uptake began. During this stretch, the N at 1' continued to be higher than at 2'. In contrast, in 2015, for most of the summer, the 2' samples had higher nitrates than at 1' because the 16" of rain pushed N farther into the soil. 

In southern Michigan, Farm Journal Associate Field Agronomist Missy Bauer found similar results. Over a three-year span, on the same irrigated corn-on-corn field, she studied four scenarios to evaluate N timing on the front end versus the back end: 95 lb. N upfront, 90 lb. sidedress; 110 lb. upfront, 75 lb. sidedress; 155 lb. upfront, 30 lb. sidedress; and 185 lb. upfront, 0 lb. sidedress. In addition, all treatments received 30 lb. N via fertigation at V10 and again at tassel.  

In 2015, a N-deficient year, the corn showed a big yield increase, up to 36 bu. per acre, to the 90 lb. and 75 lb. applied on the back end. In 2014, a similar year, the response was 21 bu. However, in 2016, an N-friendly year, yield responses to the N applied on the back end were minimal. 

“In 2016, there was little denitrification or leaching and mineralization was better, meaning it created it’s own back-end N, Bauer says. “Therefore, you have to tweak and tailor your N program on an annual basis based on the present environmental factors.” 

Placement. Back in central Illinois, Ferrie and crew studied another field with four management zones, three soil types and a base N rate of 110 lb. (fall dry fertilizer, spring broadcast and planter applications). The field included three variable-rate N trials: All N sidedressed at V5 with a coulter (trial #1); all N sidedressed at V12 with 360 Y-drop (trial #2); and split N application at V5 and V12 (trial #3). (See chart above.) 

Before each application, soil nitrates were pulled to determine the N rate. At V5 (May 3), nitrate tests indicated the corn needed a variable rate from 90 lb. to 120 lb. In trial #1, a 90 lb. to 120 lb. variable N rate was sidedressed with a coulter. In trial #2, zero N was applied. In trial #3, a variable N rate of 45 lb. to 60 lb., a half rate, was applied.

When the corn reached V12 (June 14), nitrate tests were pulled on trials #2 and #3. In trial #2, the tests showed the corn needed a variable N rate from 120 lb. to 150 lb. Tests in trial #3 indicated the corn needed an additional 60 lb. to 75 lb. variable rate bringing trial #3’s total application to 105 lb. to 135 lb. N.  

This plot showed little yield advantage across management zones from a double split N application, which means N was not the limiting factor. 

However, in the sandier soils of Michigan, Bauer ran a similar study on three farms and found split N applications paid off (see bottom chart above). There was an average 7.4-bu. increase from splitting the applications (half V3-V5 with a coulter and half V9-V10 with a Y-Drop) versus sidedressing at V3-V5 with a coulter. Delaying the in-season application to V9-V10 with the Y-Drop bumped yield 4 bu. compared with the V3-V5 coulter. When the total N rate was cut by 20 lb. with the split applications, yield dropped by almost 7 bu. per acre, showing N was a yield-limiting factor. 

Product. In Illinois, Ferrie compared a 120 lb. preplant broadcast N application with and without an inhibitor (see table on the right). In this area, the natural soil N level ranges from 30 lb. to 60 lb., without any N applied, which is important to know when evaluating the inhibitors’ N rate. Any N above the application rate is from soil mineralization. 

“The inhibitor made a difference in total N on May 18,” Ferrie says. “In this case, you can cut the sidedress rate because the field lost less N.” 


Rate. To evaluate rate, Ferrie and crew used a field with a base application of 160 lb. that needed an additional 90 lb. N sidedress (based off soil nitrates). To run rate checks, the crew went 30 lb. above and below. As the chart to the right shows, the original 90 lb. program yielded the best across the field. At 120 lb., yields decreased in all but one management zone. 

“At harvest, the corn in every 120 lb. strip was starting to fall down,” Ferrie says. “That’s common—we can make corn fall when we overapply N.” 

It’s essential to hit the right rate at the right time. Be careful to not overapply, especially on fields with a high N-supplying power. 

In the same field, the crew added 26 lb. of sulfur (acts as N inhibitor) to the three rates. (Note: 31 lb. of additional sulfur was applied via broadcast in the fall.) The purpose was to evaluate sulfur as an inhibitor, not to trigger a yield response from sulfur. Tissue samples were pulled in and out of the check that verified adequate sulfur.  

At harvest, Ferrie noticed the standability issues observed at the 120 lb. rate began to show up in the 90 lb. rate. The 60 lb. N application with sulfur performed the same or slightly better than the 90 lb. N without sulfur. 

“By adding sulfur we protected the N and made 60 lb. act more like 90 lb.,” Ferrie says.

Thank You to Our Test Plot Partners
Case IH, Jay Barth, CJ Parker and Tony McClelland; New Holland, Daniel Valen, Ken Paul, Mike Kizis and Sheldon Gerspacher; Burnips Equipment and Carl VanderKolk; Versatile and Adam Reid; Central Illinois Ag and Kip Hoke; Kinze Manufacturing, Susanne Veatch and Phil Jennings; Unverferth Manufacturing and Jerry Ecklund; Wells Equipment; Apache Sprayers; Trimble, Frank Fidanza and John Pointon; AirScout, Brian Sutton and Maykol Hernandez; Ag Leader and Luke James; Blu-Jet and Nick Jensen; Fast and Dan Liening; 360 Yield Center; Koch Agronomic Services and Steve Parrish; Yamaha; Lawrence “Shorty” Olson; John Thomas; Just a Mere Farm, Rod Wilson and Brad Beutke; Trainor Grain, Mike Trainor and Dustin Followell; Crop-Tech Consulting, Isaac Ferrie and Matt Duesterhaus; LDK Farms and Leon Knirk; Simington Farms; Jerry Reed; Terry Finegan; Jim Caldwell; B&M Crop Consulting, Bill Bauer, Amanda Anderson and Chad Roach

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