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."
- Late Spring 2012