Frequently applied to fertilizer recommendations; such as for cattleyas -- 50ppm of Nitrogen, 20ppm. of Potassium, 50ppm. of Phosphorous, plus 50ppm. of Magnesium Sulphate; one part per million is the equivalent of one ounce in 7,380 gallons of water; lOOppm. is equivalent to 4.5 ounces in 100 gallons. RMH
PARTS PER MILLION: Equivalents
One part per million (ppm.) is one ounce in 7,830 gallons of water; lOO ppm. is equivalent to 4.5 oz. ammonium nitrate in 100 gals. C72-223; OR74-135