Questions. Who is Using Molasses? and does it work?

Nullis said:

You check again, please. And don't just half-ass Google it and trust the first pot forum post that comes up (no offense). Material safety data sheet for dolomite. Second source. ... Third source. Fourth source. (These ones are for regular CaCO3 lime.)
Could also check this out: http://www.engineeringtoolbox.com/bases-ph-d_402.html

Lime will raise pH, never lower it. A lot of people seem to think it does both, or that it is 'neutral' and this just isn't the case. I don't have time to thoroughly explain pH and how it works or anything like that right now, but it's good to have a general idea of the concept. It stands for potential Hydrogen and has to do with the concentration of hydrogen to hydronium ions in a solution. In general, the more H+ ions a solution has the more acidic it is. The thing to note right now is that the actual resulting pH of X material in solution is dependent on a couple things, including temperature and concentration of the solute.

If you mix some lime in water, the resulting pH of the water is going to depend on how much lime you put in the water (and initial pH of the water). Of course, dolomite and calcitic lime are only slightly soluble in water. Notice how the data sheets variously state pH or alkalinity, for example, as a 1% solution or a saturated solution, or a slurry. A saturated solution of lime has as much dissolved in it as possible under the circumstances, no more will dissolve and would instead appear as precipitate. A slurry will have precipitate or undissolved lime in it.

Therefore, the pH of a 1% solution is between 8-9; the pH of a saturated solution is 9.4 and the pH of a 20% slurry is 10. If you have liquid pH drops or litmus paper you could easily verify this with your own eyes.



Once you water, a small amount of the Ca (and potentially Mg) contained in the lime becomes dissolved in the water (dissociates) and is thus available for uptake by plants and organisms. All of the rest of the applied lime is within the soil mix as precipitate, and it reacts with acids in the soil, dissolving over time. The calcium and magnesium ions are positively charged (cations), so they are retained by the soils negatively-charged exchange sites until needed (cation exchange capacity is an important characteristic of soil).

I hate to hear of people adding a crap ton of perlite to their potting mix. IMO this can cause a variety of problems and make it more difficult for new growers. Perlite doesn't hold water or nutrients, it has virtually no CEC and thus no buffering capabilities as soil should. A more typical usage rate for lime (without a bunch of perlite) would be one or two heaping tablespoons per gallon.

BTW if what you are experiencing is a magnesium deficiency I would recommend applying the epsom salt as a foliar spray. Mix a teaspoon or two to a gallon of water and spray this on the foliage (shortly after lights on, raise lights in needed). You can do this daily or even 2x a day in veg and you should see an improvement sooner.

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