The Farm Journal Test Plot crews evaluate different sidedress systems for feeding corn nitrogen
Sidedress nitrogen applications can bridge the gap between a corn crop’s strong start and a strong finish. However, there are many questions about timing, rate and which product to apply.
To answer these questions, the Farm Journal Test Plot crews headed to the field to look at anhydrous ammonia and 28% liquid nitrogen applications. Machinery is available to apply liquid and gas products, but price and availability are often the main drivers of a farmer’s decision.
Farm Journal Field Agronomists Ken Ferrie and Missy Bauer set up test plots in the central Corn Belt and eastern Corn Belt, respectively, to find the differences in applications.
"The key to managing your nitrogen is to sidedress green corn," Ferrie explains. "You don’t want the corn to turn yellow before you apply more nitrogen, so your upfront program has to be managed as well. But many farmers ask if there is a difference in the way corn responds to anhydrous or 28% at sidedress."
|In a replicated, multiyear test plot using one Great Plains Nutri-Pro toolbar, the test plot crew was able to apply anhydrous ammonia and 28%. Using quick couplers, the 28% could be applied using a knife or coulter inject.
Two years of data. Ferrie led the effort in central Illinois. His crew used one toolbar, a Great Plains Nutri-Pro with a Raven controller, a Raven anhydrous cooler and a hydraulic Hypro pump for the 28%. The plumbing was set up with quick couplers so that the anhydrous could be run through an anhydrous knife and the 28% could be run through either an anhydrous knife or a Great Plains Vantage 1 coulter inject. For application with the knife, the crew set the depth to ensure a good seal for the anhydrous application, and the 28% applied with the knife was run at the same depth. A Yetter All-Steer cart was used to carry the 28% product.
"We set up the toolbar so that we could compare anhydrous ammonia to 28% both knifed in with the same knife and at the same depth. Or we can compare 28% applied with the coulter inject to knifed-in anhydrous or knifed-in 28%," Ferrie says. "Many farmers ask the value of the knife as far as opening up the soil and letting some air in. So to make that comparison, we put 28% on with the coulter inject followed by the knife to do tillage, and we also put on 28% and took the knife off."
Before sidedress, the test plot crew pulled nitrate samples to determine the best sidedress rates. Test strips were run above and below that calculated rate to ensure it was optimum. Whether for anhydrous or 28%, the rates were set to apply equal pounds per acre of nitrogen.
A laptop computer in the cab interfaced with a Raven controller setup for each, the anhydrous and the 28%. The tractor was outfitted with auto-steer so the crew could map out the individual passes with each treatment, do those passes and then return to fill in the other treatment strips.
Ferrie’s test plot is a multiyear study that began in 2010. In the first year, two fields were included in the study, and in 2011, one field was included. The test fields ranged from 160 acres to 200 acres to provide well-replicated plots.
In the first field from 2010, the corn was 7" tall and the nitrates suggested a 60 lb. per acre nitrogen rate.
|Every Farm Journal Test Plot is harvested using a calibrated yield monitor and yields are cross-checked with a grain cart equipped with a scale package.
"At 60 lb. of nitrogen per acre, there was no difference between all treatments. There was no difference between 60 lb. and 90 lb., but there was a significant drop in yield when we applied less than 60 lb. It didn’t matter how we put the nitrogen on as long as 60 lb. was there for ear fill," Ferrie says.
Rainfall delayed sidedressing the second field, and the corn was at V8 and between knee-high to thigh-high by the time the field dried enough. Again, the nitrates suggested a 60 lb. nitrogen rate as optimum.
"Whether we put on anhydrous or 28%, if the knife was on the toolbar, we saw a yield reduction," Ferrie says. "We saw the stress caused by the knife in the NDVI [Normalized Difference Vegetation Index] map midseason. And at harvest, the combine operator could tell us we were in a pass with the knife just by looking at the yield monitor, even before we weighed the pass in the scale cart."
The yield loss from knife application ranged up to 18 bu. per acre. "It was confusing because we sidedressed later in the day, and there was no visual sign of the plant being under stress due to root pruning, that we could see," Ferrie says.
"We had been rained out of the plot until the day we sidedressed, and then it rained the following day. The conclusion is that we must have pruned the roots in the corn since it was further in its growth," he says.
The second year, 2011, had an extremely wet spring, causing large losses of nitrates, and the nitrate samples suggested a 150-lb. nitrogen rate was needed. The corn was V4 and about 6" tall.
"The knifed-in anhydrous, the knifed-in 28% and the coultered 28% yielded the same. But where we applied 28% with the coulter followed by the knife, we had a consistent yield reduction in every replication," Ferrie says.
Contrasting with 2010 conditions, in 2011 the field was dry.
"I believe, due to the dry conditions, that by applying nitrogen close to the surface with the coulter and also running the knife below that, we dried the soil out down to the depth of the knife and the nitrogen that we placed with the coulter ended up in a dry area. We pruned some roots and didn’t get rain to stimulate root growth, which negatively impacted yield," Ferrie says. He points out that when applying nitrogen in dry soil, rain is required to move this mobile nutrient deeper into the soil or to stimulate root growth.
"But when we look at the first two years of data, as far as the corn plant is concerned, it doesn’t matter if we are using anhydrous or liquid," Ferrie says. "And it doesn’t matter if we are applying with a coulter or a knife. However, the value of the knife as an aeration tool may be in question."
He cautions that there may be more risk and downside to pruning roots in taller corn. Additionally, by doing tillage with the knife and bringing seed to the surface increases the risk of weeds.
"The results from year two suggest that nitrogen needs to be in moisture. So if sidedressing green, healthy corn and placing the nitrogen at the surface with the coulter, farmers need rain to move the nitrogen down to the roots. But if sidedressing nitrogen-deficient corn in dry soil, I may choose to put it deeper to get the nitrogen closer to the roots, because there isn’t time for rain to move it down the soil profile," Ferrie says.
He says he likes to position sidedress applications for ear tip fill in the plant’s development, and both products tested performed similarly from an agronomic perspective.
|In the eastern Corn Belt, Missy Bauer tested sidedress products using a toolbar from Fast Distributing for 28% application.
Eastern Corn Belt results. In southern Michigan, Bauer ran tests using two toolbars: a knife toolbar to apply anhydrous, and a coulter toolbar from Fast Distributing to apply 28%.
"For us, the sidedress application product is decided mostly by availability, because not many dealers in the eastern Corn Belt carry anhydrous anymore," she explains.
One advantage to 28% is that the coulter doesn’t cause as much soil disturbance, Bauer says. If running off center, an anhydrous knife can be aggressive enough to bury V4 corn.
"Also, in a wet year, it can be more difficult to get a good seal when applying anhydrous with a knife—so those farmers may have to wait an extra day or two to get into the field," she says.
The data gathered from Bauer’s study suggests the same agronomic performance as the data from the central Corn Belt. There was no yield difference between the sidedress applications of anhydrous ammonia and the 28% nitrogen product.
More to come. The Farm Journal agronomists will continue their studies in nitrogen management.
"We will be adding an entry to the plot. Along with the anhydrous knife, we will use a streamlined knife without wings or a beaver tail used just for 28% application. This will do less tillage and be less aggressive. We were looking at the aeration factor of the anydrous knife, which is more likely a detriment, so we want to tame that down," Ferrie says.
In their effort to learn how to increase yields, the agronomists stress the fundamental purpose of sidedressing: "Farmers should meet a plant’s nitrogen demands on a daily basis so that it never has a bad day," Ferrie says. "The key to strong corn yields is to start strong and finish strong."
Thank You to Our Test Plot Partners
Each Farm Journal Test Plot is a cooperative effort. Thanks go to: Yetter Corporation and Scott Cale; Great Plains Manufacturing, Tom Evans and Doug Jennings; Fast Distribution and Brian Johnson; Case IH, Tom Dean and Tony McClelland; Kinze Manufacturing, Suzanne Veatch and Luc Van Herle; Unverferth Manufacturing and Jerry Ecklund; John Deere and Barry Nelson; Cross Brothers and Brad Cross; McCormick USA and Doug Rehor; Trimble and Brian Carlson; Novariant; Challenger and Mike Alvin; Farm Depot; Orthman Manufacturing, Adam Souder and John Bell; LeRoy Fertilizer and Bob Spratt; McLaughlin-Dooley Farms; LDK Farms and Leon Knirk; Crop-Tech Consulting, Isaac Ferrie and Brad Beutke; B&M Crop Consulting, Vicki Williams and Bill Bauer.