Save time and money next spring by testing soil nitrogen levels this fall.

Charles Shapiro, University of Nebraska-Lincoln soils specialist, says fields that will be planted to corn or sorghum next year may show higher than normal nitrates. Soil sampling for nitrogen levels following harvest will determine exact nitrogen levels.

"Fall is a convenient time for farmers to test nitrogen levels because they have the winter to develop a fertilizer plan before spring planting. In some years they also can save money by taking advantage of lower fertilizer prices," says Shapiro, soils specialist at UNL's Haskell Agricultural Laboratory near Concord.

Nitrogen generally is available for plant growth. Therefore, the purpose of nitrogen testing isn't to determine whether or not nitrogen exists in the soil, but to determine how much nitrogen is available for plant use, Shapiro says.

"Nitrogen carryover should be relatively high this year due to the drought," Shapiro says. "In situations where yields were low, a lot of the nitrogen didn't get used."

One benefit of high carryover is the decreased need to apply nitrogen fertilizer in the spring. “However, farmers should remember that nitrogen levels can decrease over the winter months. Wet winters cause nitrogen to leach below the root zone, thus resulting in a lower nitrogen levels than indicated by fall measurements.”

"It is possible that where fields received rain this fall, which increased soil microbial activity, released a flush of nitrogen."

Nitrogen tests are taken using a soil probe to collect samples from different locations within the field. It is important to take soil samples correctly. Soil probes generally are inexpensive or can be borrowed from fertilizer consultants or local extension offices.

The samples are then sent to a lab for testing. Analysis cost depends on whether a complete soil analysis is done or one only for soil nitrates. The cost for soil organic matter and nitrates is around $10-$15. A complete analysis is about $25. Each laboratory has its own combinations.

For more information about fertilization for corn, consult UNL Extension NebGuide G174, Fertilizing Suggestions for Corn, available online at http://www.ianrpubs.unl.edu/epublic/pages/publicationD.jsp?publicationId=142 or ask for it at your Extension office.