Measure Soil pH at Rest or Stirring the Soil:water Mixture?

Abstract

For soil pH measurement is necessary consider the reading time and read during stirring the mix soil:water or read in repose. We compared the measurement of pH in the supernatant from the soil mix: water (1:2.5) after 15 minutes rest or stirring sample and measure at less time. The procedures for pH measure were: i) stirred during 3 minutes + 15 minutes of rest and measuring in supernatant without stirring; ii) after stirring the mixture for 1, 2 and 3 minutes after 3 minutes of stirring + 15 minutes rest; iii) during the stirring of the mixture for 1, 2 and 3 minutes without rest. The higher soil pH values were obtained during initial stirring. These differences decreased from 5.38 % to 3.91 % after three minutes of stirring. There were no differences in pH values after three minutes of stirring with or without previous rest. There was no effect of 15 minutes rest. Measurement of soil pH at the end of the initial two minutes of stirring, with three repetitions, showed a CV = 1.41 %. The soil pH measurement at the end of three minutes of stirring the soil:water mixture would be acceptable.