Fall soil testing

By Lyndon Hicks
Regional Crops Specialist
Yorkton Saskatchewan Ministry of Agriculture


Fall is an excellent time for soil testing. It gives the producer more time to assess his or her 2016 fertilizer management plan without compromising soil test accuracy.

Fall soil sampling generally gives enough time to sample the fields, order nitrogen fertilizer, and fallband before the soil freezes. Producers, who apply all their fertilizer in the spring, can continue soil testing late into the fall.

After midSeptember, soil nutrients can be accurately measured. The availability of soil nutrients fluctuates with many factors, including soil temperature. It’s preferable to wait until the soil temperature has cooled to below 10 degrees Celsius. When the soil cools down, the mineralization of nitrogen (N)  also slows down considerably. Mineralization is the process whereby N in organic form is converted to plant-available form by soil microbial activity. The time of sampling is less critical for soil phosphate (P2O5), potassium (K2O) and other nutrients. Soil testing involves three steps: collecting, analyzing, and recommending. At its most basic, soil testing involves collecting soil samples that best represent that field; choosing a lab to analyze; and developing nutrient recommendations from the analysis. Getting the most from a soil test requires collecting a representative soil sample, identifying a laboratory whose analysis and recommendation philosophy conforms with the producers’ nutrient management objectives, and providing that laboratory with all the pertinent information it requires.

Tips to successful fall soil testing:

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  • Know your field history – make sure your sample is representative.
  • Take enough samples a minimum of 1520 per quarter; May need more if field is highly variable.
  • Keep the sample cool – send to lab as soon as possible while maintaining a stable cool temperature.
  • Avoid hot spots – a hot spot refers to a small pocket of soil with high nutrient densities.
  • Contact your lab of choice prior to sampling – different labs have different protocols and sampling techniques.


The analysis techniques and recommendation philosophies differ with each individual laboratory. However, they all use the best technology and information required to analyze and make recommendations. The quality of the laboratory analysis and the accuracy of the recommendations will depend on the quality of the soil sample and the information the producer provides about that field, including the previous crop grown and crop selection options for the next growing season.