Evaluating Accuracy and Precision of ‘Hand-Held' Soil Testing Meters As Compared to Traditional Soil Test Methods for Potassium, Calcium, Sodium, Electrical Conductivity, and Soil pH.

The United States Northern Great Plains soils, particularly South Dakota and North Dakota, are populated with areas where salts predominate at the soil surface.  Over the past 20 years, climate change has caused increased precipitation.  Crop rotational management has migrated from grasslands-pasture/wheat/ fallow to corn/soybean/wheat rotations.   Geological deposits in this region contain calcium, magnesium, and sodium salts.  The combination of increased precipitation, reduced crop water usage, and shallow salty soil deposits have increased the development of ‘alkali’ or salt areas in agronomic fields.  Traditional soil testing methods to evaluate the presence of total salts is measuring soil electrical conductivity (EC).  Sodium concentrations are typically evaluated using either Sodium Absorption Ratio (SAR) or Estimated Percent Sodium (ESP).  Recently, hand held soil testing meters to measure sodium, calcium, EC, etc. have become available.  Use of the hand held meters to test soil salts has been questioned by crop consultants in this area.  Recommendations to apply soil amendments are determined using the results from the soil analysis for salts.  The study objective is to compare the soil salt results between hand-held units and traditional soil salt test methods.   Results presented in this study will compare the salt concentrations as measured with these meters to traditional methods of cation concentrations using (1) ammonium acetate extraction and (2) saturated paste extraction.   Recommendations provided to crop consultants regarding the accuracy and precision of these instruments as compared to traditional soil test methods will be presented.