Is there any proposed or established rating of low, medium, and high calcium carbonate content in the surface soil?
What is the minimum amount of calcium carbonate content that should be present in the surface layer for a soil to be called "Calcarous"?
When we estimate free calcium carbonate by rapid titration method that should also include free magnesium carbonate or free dolomite. Why can't I find any mention of magnesium carbonate in the literature when it comes to rapid titration method?
sorry, I don't know if such a classification exists. However soil scientists usually make a difference between "active carbonate" and "inactive carbonate". Depending on the granulometry of the limestone elements (sand, gravel, etc.) and on the calcite crystalline forms (micrite or sparite) the carbonate fraction in a soil does not react in the same way. Dolomite is also a carbonate indeed, but less reactive than calcite in soils.
A calcareous soil should have more than 40% Ca carbonate. Calcareous soils are common in black soils (pararendzina, rendzina, and arid sols). Calcareous concretions are common to soil types derived from loess, marl. These Ca—enriched soils are deprived of trace elements essential for plant nutrition. High Mg contents are only present on basic and ultrabasic bedrocks which also are poor in K . The calcium dynamic in the pedosphere is a very complex subject matter controlled by the pH, environment of deposition/formation, climate and the bedrock
HGD
Dr. Harald G. Dill , thanks for answering my question. I am wondering, isn't 40% too high?
Classification based on mass %
< 0.5 c1 very poor in carbonate
0.5 to 2 c2 poor in carbonate
2 - 10 c3 carbonate-bearing
10 - 25 c4 enriched in carbonate
25 - 50 c5 very strongly enriched in carbonate
50 - 75 c6 extremely enriched in carbonate
≥ 75 carbonate (limestone, calcrete, dolocrete..)
Elaborated for soil types in German vineyards
HGD