Soil Test This Fall to Determine Fertilizer Need

Soil Test This Fall to Determine Fertilizer Need

September 28, 2007

U.S. High Plains map showing precipitation over the last year.
Percent of normal precipitation for the last 365 days (in inches) for the High Plains Region

Fall harvest has begun and it's not too early to think about next year's fertilizer needs. Fertilizer prices are at historic highs with nitrogen and phosphorus costing nearly 50 cents a pound in most liquid and dry sources. The spring outlook is for prices to stay at current levels or increase slightly due to world demand. (Planting has started in South America and there is strong demand in India and China.) These reasons highlight the importance of soil sampling to determine nutrient availability as a planning tool for buying next year's fertilizer.

Corn is Nebraska's largest user of nitrogen so sampling fields that will be corn in 2008 should be a priority. Knowing your soil phosphorus level is also important due to high phosphate prices.

Nebraska experienced rainfall extremes this year which likely affected soil nitrogen levels. West central to eastern Nebraska had above normal rainfall this spring and early summer while much of the Panhandle is still in drought conditions. Varying corn yields due to nitrogen leaching, disease or weather damage also cause variability in soil residual nitrate-N. Because soil nitrate is mobile, soil sampling is the only reliable way to determine how much is in your soil. Soil samples for nitrate should be taken to at least a three-foot depth for next year's corn crop.

Information Resources 

  • The UNL NebGuide, Guidelines for Soil Sampling (G1740), was recently updated and provides recommendations for field division, sample numbers and sample depths.
  • To see the impact of current fertilizer and corn prices on nitrogen recommendations, use the Excel spreadsheet available on the UNL Soil Fertility Web site at http://soilfertility.unl.edu/.

A good job of soil sampling this fall will be an investment that can pay big dividends next year. Remember that old saying, "Don't guess, soil test!"

Gary W. Hergert
Extension Soils Specialist
Panhandle REC, Scottsbluff