Insights on When Corn Uses Nitrogen

Photo: Jason DeBruin

By Jason DeBruin
Research Scientist, DuPont Pioneer, Macomb, Illinois

Jason DeBruin, a DuPont Pioneer research scientist based in Macomb, Ill., discusses what we're learning about nitrogen use in corn. As yields increase, modern hybrids are taking up more nitrogen later in the reproductive stages. This may impact when and how growers supply nitrogen to corn.

Q:  Are today’s hybrids any different from historical hybrids in their nitrogen usage?
 
A:  Growers are obtaining almost twice the yields in corn with little change in the total amount of nitrogen (N) applied. In the past, we assumed if we had enough N in the soil through flowering, the plant would take it up before tasseling and, from that point on, the plant would remobilize N from leaves and the stalk to fuel grain fill.
 
Chart: Historical grain yields and nitrogen application rates on corn acres in the U.S.
Historical grain yields and nitrogen application rates on corn acres in the U.S. (Source: USDA.)
 

The capacity of the plant to store N in the leaves and stalk by flowering hasn’t changed much, but we know today’s hybrids are taking up more total N than previous hybrids over the entire season. The demand for N postflowering is greater than it used to be. That N has to come from somewhere. It appears the roots are continuing to take up nitrogen from the soil well into the reproductive stages. This means the soil must have enough N available at this time to maximize yield potential.

We still have a lot to learn about the mechanisms for this later uptake of N, but it could be the ear is signaling the plant it needs more nitrogen than the plant stores can provide. The accompanying tables show N uptake from the plant and from the soil in normal and low N environments.

Seasonal N uptake (lbs N/acre) for hybrids grown under normal (left) and low (right) N supply near Sciota, IL, 2011.
Seasonal N uptake (lbs N/acre) for hybrids grown under normal (left) and low (right) N supply near Sciota, IL, 2011.
 
Q:  How may this shift in N needs change the ways growers manage this nutrient?
 
A:  We encourage growers to ensure yield potential and yield stability by timing N applications to meet the crop’s demand. If N is applied in fall or even in spring, it may run off or leach away, leaving the soil without enough N to fuel higher yields.

Growers who are aggressive in timing N applications to meet the plant’s needs may save money, use less N overall and lose less into the environment. The ramifications of the latter are growing.

It takes a lot of work, but there’s a lot to gain. The newly offered EncircaSM services from DuPont Pioneer can help growers use field data over multiple years to gain insights into better ways to time N applications.

Illustration: Percent of N taken up by the plant before and after flowering, and percent of N in the grain from postflowering (after VT-R1) uptake and remobilized sources.
Percent of N taken up by the plant before and after flowering, and percent of N in the grain from postflowering (after VT-R1) uptake and remobilized sources.
 
Q:  How are growers changing how and when they apply N?
 
A:  Much of what growers do today depends on their equipment. Can they get into the field to apply N near flowering?

It's important to realize each year is different. Some years, a grower can apply, say, 180 pounds of N per acre in spring and that will suffice into reproduction with little to gain from late season N. Other years, if for example it's been wet, growers may apply additional N at tasseling and receive a significant yield boost. We used drip tape last year to supplement N at tasseling and saw a yield bump of 10-15 bu/A.

DuPont Pioneer is working on improving nitrogen use efficiency in corn hybrids, but it will take new products along with changes in grower management practices to fully impact yields. DuPont Pioneer researchers, corn breeders and agronomists are working to help growers with the entire package. It’s an exciting time to be working on nitrogen use in corn.

Get more insights into the timing of N uptake and sources of N utilization by corn.


The foregoing is provided for informational use only. Please contact your Pioneer sales professional for information and suggestions specific to your operation. Product performance is variable and depends on many factors such as moisture and heat stress, soil type, management practices and environmental stress as well as disease and pest pressures. Individual results may vary.

 

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