The Spurway Method employs a weak acetic acid extraction of soilless potting media. A representative sample of the media is sieved through a 2.38-mm screen to remove large pieces of bark, stones and other relatively inert materials. A 5-cc subsample is placed in a 50-mL Erlenmeyer flask and 25 mL of 1% acetic acid solution is added. The mixture is shaken for 1 minute and then filtered.

The filtrate is analyzed for important plant nutrients: Nitrate and ammonia are determined by colorimetry, and phosphorus, potassium, calcium, magnesium, sodium, iron, manganese, zinc, copper, molydenum, and boron are analyzed by ICP-OES. Results are reported as ppm (mg/L) in the media extract.

A separate 15-g subsample is wetted with 75 mL of deionized water, stirred every 10 minutes for 40 minutes and then analyzed for electrical conductivity.  Media pH is determined on a separate 10-cc subsample that is wetted with 10 mL of deionized water, allowed to stand for 15 minutes, and then measured on a Mettler Toledo Seven-Multi pH meter with an InLab Routine Pro combination electrode.