http://www.greenhousegrower.com/art...ant-nutrition-limestone-calcium-and-magnesium Apparently it is not as effective for providing calcium to the soil. Thoughts / opinions? "Research at Michigan State University tested the effect that a dolomitic limestone had on pH and calcium concentrations for the first four weeks after mixing (Figure 1). It was shown that the reactive fraction of the limestone had little effect on root-medium calcium concentrations, even as the limestone continued to react. It appears that once the calcium from the reactive limestone is bound to the peat, it is not released back into the soil solution under most conditions. Since nutrients must be soluble to be taken up by the plant, the bound calcium does not influence calcium nutrition, either in the short term (mixing to stable pH) or the long term (stable pH till the end of the crop). It also may explain the reason that cation exchange capacity of a limed peat has minimal influence on pH buffering. "