- Author: Mark Bolda
Great article here by Dr. Robert Mikkelson from the International Plant Nutrition Institute concerning the why and how of liming a soil which is acidic.
Here's the short of it:
Several factors contribute to the acidity of a soil, one being the geologic composition of the base material, another being lots of rain which leaches out calcium and magnesium. Another contributing factor to soil acidity in agricultural soils is the continual use of nitrogen fertilizers, especially in the same spot over a longer period of time. Both urea and ammonium, when converted to nitrate by soil micro-organisms, release hydrogen ions, the higher the concentration of which raise the acidity of the soil.
A common grower solution to acidic soils is the addition of ground limestone. However, while limestone neutralizes acidity, adds calcium and enhances the solubility of phosphate (and consequently availability of phosphorous to the the plant) does not dissolve well at all at pH's above 6.5 (common for soils of the Central Coast) and one would be hard put to realize the aforementioned benefits at this pH. So if one needs to add calcium to a soil with a pH above 6.5, the better choice would be gypsum, which while it also does not dissolve well in a neutral pH soil, does supply more soluble calcium./span>