LaMotte AST Series Professional Soil Test Outfits - Manual (Page 8)

UNITS OF MEASURE
All tests in the AST kits measure the concentration of the nutrients that
are available to the plants. The tests are conducted on soil extract, the
liquid formed by removing the nutrients from the soil. Since extraction
procedures remove varying amounts of nutrients, the test is dependent
upon the time and extracting solution used.
Test results are expressed in the following terms:
Parts Per Million
(ppm) Pounds Per Acre =
(lb/acre) Low To High
Calcium Nitrate Nitrogen Manganese
Magnesium Phosphorus Aluminum
Copper Potassium Humus
Sulfur Ammonia Nitrogen
Chloride Nitrate Nitrogen
Iron
=
Pounds per acre represents the number of pounds of soil in an acre to a
depth of 6 inches, or 2,000,000 pounds. Conversion from pounds to acre
to parts per million, or vice versa, can be accomplished using the
following equations:
ppm x 2 = lb/acre
lb/acre x 0.5 = ppm
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