This protocol if for use with the Hellige-Truog Soil pH Tester by Lovibond. The Hellige-Truog Soil pH Tester is a colorimetric field kit designed for rapid estimation of soil pH without the need for electronic equipment. Developed in the early to mid-20th century, it was widely used for soil testing in agricultural extension and educational contexts. While largely outdated today, it remains an illustrative tool for teaching soil chemistry fundamentals.
Procedures
Add sample to well
Add 2 drops of Reagent No. 697-27 Triplex Indicator to a cavity of the test plate.
With a spatula, add gradually just enough of dry pulverized soil sieved to <2 mm into the cavity of the test plate to absorb the indicator.
Mix the sample thoroughly with the spatula, make sure there is no excess reagent.
Open the No. 697-26 Soil reaction powder vial, and ensure the mesh plate is in place.
Gently tap of the bottom of the vial to cover the soil surface uniformly so the colour of the soil is entirely hidden.
Wait 2 minutes and compare the colour assumed by the powder to the standard colour chart. Estimate to the nearest pH.
Add reagent to sampleAdd reaction powder to sample and reagentCompare sample to calibrationIN THE FIELD - it may be easier to add the soil to the test plate prior to adding the Reagent No. 697-27 Triplex Indicator.
