ppm Charlie
Well-Known Member
Do you even test Pro Mix (PM) for media pH? According to the PM mfg website (doing the reading for you here Regrowth here):You seem to be confused about what "trust but verify" means Charlie. It means you verify, not me! I already told you it's best used within 1 year of that date. Trust me but go verify it.
I'm on the road at the moment so I'll answer these when I get back to the office!
PM is “packaged with relatively low moisture, so the limestone does not activate for some time; therefore, freshly packaged growing media may have a pH of 4.5-4.9 (saturated media extract test method or S.M.E.). Over time, the limited moisture within the package of an unused growing medium slowly dissolves the limestone, resulting in an older, unused growing medium having a higher pH than when it was first manufactured. This change in the pH will occur a little faster if the moisture content of the growing medium is higher. Typically the pH of an unused PRO-MIX product that is 4-9 months old is 5.2-5.8 (S.M.E. method), depending on the product and the moisture content. A growing medium should be used within nine to twelve months of its manufacturing date to ensure that the pH of the unused growing medium is not too high.”
(From: Low pH of Fresh Growing Media | PRO-MIX)
Therefore, if PM is 4-to-9-months old it may have low pH (less than pH-5.5). However, if PM is 12-months old it may have high pH (greater than pH=6.5). Just saying the pH of PM is ever changing and should be measured before using and adjusted if necessary based on age of the product.
The mfg website says that and shows you how. Just saying you shouldn't just use water or soil-media without knowing the pH of the media.
PM is like a fine wine - no more than 4-months old and less than a year-old is best use. But who knows, really? The pH of PM is always on the move (according to the mfg'r).