Nailing down nitrogen (N) efficiency is part of fine-tuning the management of your corn crop. The key to N management is using all the available tools and being responsive if N demands change during the growing season.
There are multiple factors contributing to corn's N needs: crop rotation, soil type, residue management, environment and hybrid selection.
"It has long been thought that corn hybrids respond differently to nitrogen applications and timing,” says Farm Journal Field Agronomist Ken Ferrie. "With better management, corn yields will go higher. The key is for corn to never have a bad day. That means hybrids should be supplied with adequate nitrogen at the necessary times.”
For the past three years, the Farm Journal Test Plots have partnered with AgriGold Hybrids to take this theory to the field. This report wraps up what we've learned.
AgriGold classifies its hybrids into seven genetic family groups. Each group has a recommendation for when and how its hybrids will respond to different crop production variables. The genetic families are formed according to their response to population, row spacing, yield environment, N timing and fungicide efficacy.
"We've been using the genetic family approach since 1999. Our hybrids are grouped into families based on their genetic makeup,” explains Mike Kavanaugh, AgriGold agronomy manager. "We go deep into the characteristics we know about our hybrids and explain the difference in how the genetics perform.
We can match a farmer's production practices to how the genetics will respond in their corn-growing environment.”
In 2008, the concluding year of our effort, seven hybrids were planted in 16-row replicated strips. Each agronomic family was included. Using GPS and automated steering to find the mapped passes across the field, we were able to plant all of one hybrid before switching to the next. This field was in soybeans the previous year.
We varied the N program uniformly across all of the hybrids. The plot included three N treatments: 200-lb. preplant; 120-lb. preplant and 80-lb. sidedress at V6; and 120-lb. preplant, 40-lb. sidedress at V6 and 40-lb. sidedress at tassel.
For the late season sidedress application, we used a high-clearance Hagie machine outfitted with an N toolbar to tower over the rows.
In 2008, wet conditions early in the season resulted in N deficiency, which caused the corn that had the full allotment applied before planting to stay green. The other treatments, which had the partial N amount, turned pale green before sidedress application.
The N deficiency penalized yields in most of the hybrids except the two that preferred late season–applied N. This was especially apparent in the low-lying ground.
"In our three-year study, it's been observed that when hybrids are upfront users they need to be managed that way. In years with early season nitrogen deficiencies, those hybrids may need to be rescued quickly to avoid a yield penalty,” Ferrie says. "Hybrids that are later users of nitrogen can be brought back easier with sidedress application.”
The plot crew didn't have to wait until harvest to see the effect of the N deficiency on yield. We used normalized difference vegetation index (NDVI) aerial imaging services from GeoVantage and a plot partner with a noncommercial technology.
With the three timed NDVI maps of the field, the plot crew could easily pinpoint the treatments where corn was suffering from early season N deficiencies. After the V6 sidedress and late season sidedress applications, the maps showed that the hybrids preferring late season N recovered while others had passed the point of being able to recover yield potential.
NDVI maps are just one form of technology you can use to increase corn yields. In the quest for higher corn yields, you should maximize all of the tools in the agronomic toolbox to account for crop rotation, soil type, residue management, environmental factors and hybrid selection.
From beginning to end. "In an effort to never let corn have a bad day and keep it green, you have to manage the whole process,” Ferrie says. "You do this by respecting the impacts of nitrogen availability due to the level of carbon present. I call this the carbon penalty, and you have to understand how large volumes of crop residue lead to the immobilization of nitrogen in your fields.”
Ferrie says the next step is to factor in weather conditions, which can leach or denitrify applied N. Weather and environmental concerns can put unforeseen wrinkles into your N management plan. Be prepared to respond to a wet spring or heavy rains early in the growing season.
"In addition, have an indication of what the nitrogen supplying power from the soil will be,” Ferrie says. "Typically in light soils, you'll need to apply more nitrogen, whereas heavy soils need less nitrogen.”
Combine what you know about your fields and a hybrid's response to N when deciding hybrid placement and N management.
"In corn-on-corn or fields with a high carbon penalty, take extra caution in managing nitrogen with hybrids that prefer it early,” Ferrie says. "If you put hybrids that like nitrogen late on soils with high susceptibility to leaching and denitrification, a late season nitrogen application may be beneficial.”
Ferrie emphasizes that corn responds to good management; seek out information to be a better manager of your crops and fields.
After concluding this multi-year effort on the hybrid preference of N application, we launched a new test plot, working with AgriGold to continue to build upon our N management knowledge. We look forward to reporting our findings on how fixed and flex ear types respond to varying population and N treatments.
Thank You to Our Test Plot Partners
Each Farm Journal Test Plot is a cooperative effort made possible by those who contribute time, equipment and inputs. Our thanks go to: AgriGold Hybrids, Mike Kavanaugh and Amy Bousley; New Holland, Greg Kieswetter, Gene Hemphill and Holly Fritz; Case IH, Tom Dean, Julie Rudnick and Travis Meier; John Deere and Barry Nelson; Cross Brothers Implement and Brad Cross; Unverferth Manufacturing and Jerry Ecklund; Kinze Manufacturing, Susanne Veatch, Matt Miner and Mike Feldman; Hagie Manufacturing, Alan Hagie, Tom Frost and Gary Morris; GeoVantage and Nick Morrow; Pinnacle Ag and Nicholas Emmanuel;
Dewain Davis; Joey Massey; Don Schlessinger; Crop-Tech Consulting, Isaac Ferrie, Brad Beutke and Kevin Mohrman.
You can e-mail Margy Fischer at email@example.com.