Optimizing the timing of nitrogen applications on winter wheat is the most important factor to achieving a response in both yield and protein.

Adequate N levels promote tillering and large head size, and are the primary factor determining the protein level of the grain at harvest. If wheat protein has consistently been below 11.5% in the past, consider some changes in N management to boost that number.

Spring is the ideal time to apply N to winter wheat to ensure top yields. Scouting the field after winter for winterkill, crop condition and soil moisture helps to determine the crop’s yield potential. By judging the yield potential of the wheat and knowing what residual N is available in the soil, a nitrogen management plan can be developed.

Early spring also is an opportune time to take soil samples on each field if samples were not taken in the fall.

Different recommendation

The N recommendation for Nebraska is different than other states. The recommendation considers the price of wheat and fertilizer to achieve the greatest economical return — not necessarily the greatest yield or high protein levels. The formula is:

Nitrogen Rate (pounds/acre) = ((N Price / Wheat Price) + (NO₃-N/68.7) – 0.235)*-725

N price is the dollars per pound of nitrogen fertilizer, and wheat price is in dollars. NO₃-N is the average parts per million (ppm) nitrate-N in the top three of the soil profile.

In order to get the highest return on an N application, N should be topdressed no later than two weeks before jointing. This is during the period when wheat is actively tillering and growing.

Head size is determined when wheat reaches Feekes 5, and any N that has been applied needs to have been moved into the root zone with moisture before that critical period to be available to the plant. Because precipitation events can be unpredictable, it is recommended to apply N before Feekes 3 or 4 to ensure the N reaches the root zone.

If only a small amount of N is needed, applying N at the same time as your spring herbicide application can save time and money. Most herbicides can be tank-mixed with UAN without losing efficacy. Check herbicide labels for compatibility.

When applied with herbicides, the N will be more uniformly spread over the wheat plants. Although this type of coverage is ideal of herbicide and fungicide applications, it can cause severe leaf burn when applying high rates of UAN in this manner.

Rates that deliver up to 20 pounds of N using this method will cause only minor leaf burn. UAN rates can be greater (not to exceed 40 pounds) if no surfactant is used or if applied during cool, nonhumid weather.

If greater amounts of N are needed, topdressing with either UAN solution using streamer nozzles or spreading dry urea are the most common methods. Each can be equally effective if properly applied. The type of N used usually is determined by price and application equipment availability.

When UAN is applied in no-till situations with heavy residue from the previous crop, some N may be tied up in the residue. Using streamer nozzles to concentrate the UAN in a few bands helps the N to penetrate through the residue. Similarly, dry urea can fall through much of the residue and avoid being tied up, which is one benefit of using a dry form of N.

Price considerations

Keep in mind that any decision on N applications should consider the price of both wheat and N. Some N will remain in the soil and in the residue and will benefit the following crop.

It can be said that you get out what you put into something. Wheat is no different. Wheat removes about 1.2 pounds of N per bushel, and not all N applied will be removed at harvest.

Nitrogen management is only one piece of the puzzle. Adequate fertility provides the basis for potential grain yield and protein levels. Variety, precipitation and pest management account for the majority of the remainder.

Get your wheat off to the best start by giving it the N it needs to reach its potential.

Creech is a Nebraska Extension dryland cropping systems specialist.