By Charles White
Liquid calcium products are a mainstay in the vast marketplace of less-than-reputable soil fertility amendments. Most liquid calcium products I encounter are a solution of dissolved calcium chloride, with a density around 11 lbs/gallon and a calcium analysis of 10% by weight. A gallon of product with these specifications contains 1.1 lbs of calcium, and recommended application rates ranging from 2 to 5 gal/ac would apply 2.2 to 5.5 lbs calcium per acre. This is a very small quantity of calcium in the scheme of things. For reference, the “plow layer” (6.66” depth) of a typical agricultural soil in Pennsylvania (a CEC of 10 meq/100g and a base saturation of 65% calcium) already contains 2,600 lbs/ac of exchangeable calcium. It’s also worth comparing the cost and calcium content of liquid calcium to limestone. Interestingly, a gallon of the liquid calcium costs about the same as a ton of limestone, but the ton of limestone contains 800 lbs of calcium (assuming it is pure calcium carbonate) compared to only 1.1 lbs of calcium in the gallon of liquid product.
Doing the math on the liquid calcium products is a sobering exercise. But you might still be convinced to buy the liquid calcium product after reading the marketing literature, which does a great job of blending truth, half-truth, and non-truth into a believable argument. One of the typical claims is that the liquid calcium is instantly soluble, whereas limestone takes several months to dissolve. This is true. If you want a pound or two of instantly soluble calcium to join the more than 2,000 lbs/ac of calcium that is probably already in your soil, then an application of liquid calcium would do just that. However, if your soil needs calcium it is much more economical to buy a ton of limestone and wait 6 months for it to dissolve.
Another claim is that liquid calcium will instantly increase soil pH by raising the base saturation of calcium on the CEC. This is a half-truth. It is true that there is usually a relationship between base saturation and soil pH. Theoretically, a calcium ion could displace a hydrogen ion on the CEC, causing that hydrogen ion to leach slightly deeper into the soil profile. However, the miniscule quantity of calcium applied in recommended application rates of liquid calcium products is not going to be able to provide nearly the quantity of calcium needed to change the soil pH through displacement of hydrogen ions on the CEC. And liquid calcium products, once they displace a hydrogen ion, do nothing to neutralize that hydrogen, so the hydrogen ion is either going to just move a few inches down in the soil profile, or more likely, just land back on the CEC in the same place since hydrogen has a greater affinity for cation exchange sites than calcium. In order to truly neutralize acidity in the soil, you need a product capable of creating a hydroxide molecule (OH-), which includes traditional liming products made from calcium or magnesium carbonates, hydroxides, oxides, or silicates.
One of the most dubious claims I have seen on liquid calcium products is that they are superior sources of calcium compared to limestone because they are not diluted by the other components of the “rock” that are not calcium. What they mean by this is that pure calcium carbonate limestone is only 40% calcium, so they are discarding any benefit to the 60% of the material that is the carbonate part. However, the carbonate part of the rock is what neutralizes acidity, actually providing a great deal of value. Interestingly, the liquid calcium products don’t mention that only 10% of their product by weight is calcium, the other 90% being water and chloride molecules, which have little value.
Based on the actual calcium content, the chemistry, and the cost of liquid calcium products, it becomes very clear that they are no rival to traditional limestone for supplying the calcium and acidity neutralization needed in Pennsylvania ag soils.
Source : psu.edu