|MadSci Network: Earth Sciences|
Hi There are two generally accepted methods for measuring soil pH The official and rarely used method calls for usin a 0.011 Molar soution of Calcium chloride. This creastes an ionic strength similar to what might be found in soil water and therefore diplacing a few more protons thatn would be found in distilled water. The other involves using distilled water. The latter approach almost always gives a higher pH valu (about 0.5 units in a typical forest soil) The bigger question might be what proportion of water and soil you should have in your mix. In general the answer is that one should use only as much liquid as is necessary to allow you to submerse your probe. The actual proportion varies depending on how much organic matter is in your soil. Finally, after mixing the soil and liquid, it is very important to allow the suspension to settle as clay particles can migrate pst the electrod and cause instability (drift) in the readings. The important thing is to report HOW you made the measurements. Good Luck!
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