Contacts:
Catherine Dehdashti, U of M Extension, (612) 625-0237, ced@umn.edu
Andrea Johnson, Assistant Editor, Minnesota Farm Guide, (320) 289-2256

Source:
Dan Kaiser, U of M Extension soil scientist

Test soil for better economic and environmental results

ST. PAUL, Minn. (9/22/2008)—Prices for nitrogen, phosphorus and potassium are high, so corn and soybean growers need to make certain that fertilizer is placed correctly for the 2009 growing season.

Dan Kaiser, University of Minnesota Extension soil scientist, encourages growers to take soil samples as a best management practice. "If taken the right way, soil sampling can be a valuable tool in managing crops," said Kaiser.

Kaiser makes the following soil sampling recommendations:

• Short on time? It's possible to test for phosphorus and potassium levels in soybean fields ahead of harvest. There may be some fluctuations in soil tests throughout the season, but that should not matter as much if you sample at the same time every time within a field. After harvest is still the best time to take soil samples.
• Remember only 1 to 2 grams of soil will be tested out of a soil sample. Any contamination can severely affect the results potentially causing fertilizer to be under- or over-applied. Be sure to bring in a high quality sample for testing.
• Timing for sampling nitrogen is critical, and should be taken when temperatures move below 50 degrees for best results. When soil temperatures are warmer, nitrogen mineralization occurs. The soil test may not accurately report nitrogen levels, and you may actually wind up over-applying fertilizer, which can add up to quite a few dollars per acre with today's prices. With fertilizer needing to be booked early, it may be difficult to wait, but it is still best to get accurate results from a soil sample.
• Soil samples can be taken and used to gauge the need for micronutrients, with a few exceptions. For sulfur, a 0- to 6-inch soil sample is not a reliable test except in sandy coarse-textured soils.

More information on soil testing is found on Kaiser's blog located at http://AgBuzz.com. AgBuzz is a cooperative blogging effort of University of Minnesota Extension and Minnesota Farm Guide.

URL: http:// www.extension.umn.edu./extensionnews/2008/test-soil.html  This page was updated Sept. 22, 2008 .
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