LaMotte STH Series - Manual (Page 23)

Units of Measure
Test results are expressed in the following terms:
Parts per Million
(ppm)
Pounds Per Acre
Relative Amounts
from Very Low to
Very High
Nitrite Nitrogen Nitrate Nitrogen Ammonia Nitrogen
Calcium Phosphorus Magnesium
Sulfate Potassium Aluminum
Chloride Iron Manganese
Pounds per acre represent the number of pounds of soil in an acre
to the plough depth of 6-7 inches, or 2,000,000 lbs. Conversion
from pounds per acre to parts per million, or vice versa, may be
accomplished by means of the following formulas:
ppm x 2 = lb/acre
lb/acre x 0.5 = ppm
In the four nutrient tests which produce relative test results, the
following approximate quantitative values may be assigned to the
relative terms:
Approximate Value Expressed in ppm
Test Factor
Very Low
(Low)
Low
(Medium
Low) Medium High
Very
High
Ammonia Nitrogen 5 10 40 100 150
Magnesium 5 10 25 80 150
Aluminum 5 10 30 80 125
Manganese NA 5 12 25 40
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