March 16, 2007

Nebraska farmers planted significantly more winter wheat across Nebraska this past fall due to improved prices and in some cases, reduced water availability. Much of the wheat planted received limited nitrogen. Now is an excellent time to evaluate stands and check soil moisture and fertilizer prices to determine if additional nitrogen is needed. Wheat prices have remained high and if you didn't buy fertilizer last fall or early winter and haven't checked fertilizer prices in the past four to six weeks, you're in for a surprise. With the additional acreage expected to shift to corn this spring, demand for nitrogen has significantly increased nitrogen prices. If only a portion of the required nitrogen was applied last fall, nitrogen needs to be applied soon.

Spring Nitrogen Management

How much nitrogen do you need to apply this spring for wheat? First, assess current soil nitrogen by testing a soil sample taken to a three-foot depth for residual nitrogen. (Take this test as soon as possible unless you took it last fall.) Table 1 shows recommended nitrogen rates that reflect current price ranges for wheat and nitrogen rates calculated from the wheat nitrogen algorithm. (For further detail see UNL NebGuide Fertilizing Winter Wheat I: Nitrogen, Potassium, and Micronutrients (G1460).

For irrigated wheat, current guidelines suggest adding an additional 20 pounds of nitrogen to the recommended levels.In most areas this may be sufficient, however, a better approximation may be to add 1.5 pounds of nitrogen per bushel above the 75 bu/ac yield level if you have consistently produced above that level. Simply adding more nitrogen will not "enhance" yield potential. Many other production factors (seeding rate, variety, planting date, row spacing, irrigation timing, weed, disease and insect management) are controlling factors for consistently high yields. A web-based Excel calculator for nitrogen recommendation for wheat is available online at http://soilfertility.unl.edu. NebGuide 1460 can also be used to calculate nitrogen recommendations.

Nitrogen Sources Nitrogen Solutions

Determining viable stand is equally important for weed control decisions as it is for nitrogen fertilization decisions. If nitrogen solution-herbicide combinations are used, they should be applied early for many broadleaf weed problems. Early nitrogen allows more time for distribution into the root zone but may be too early to control some weeds. Later applications may be optimum for some weeds but may cause problems with plant injury because of the herbicide-fertilizer combination.

Urea

Urea (46-0-0) is a good choice for spring topdressing if applied early. The cooler temperatures and the higher probability of precipitation helps assure a lower potential for nitrogen volatilization loss. See the March 9 article ( Managing Urea-Based Fertilizers for Maximum Benefit) and previous CropWatch articles on managing urea-based fertilizers.

Gary W. Hergert
Extension Soils Specialist
Panhandle REC, Scottsbluff