404 THE PRINCIPLES OF SOIL MANAGEMENT 



bacteria upon mineral matter than merely the solvent 

 action of these acids. That rock may be disintegrated 

 through the action of bacteria has been already com- 

 mented upon. Although it has not yet been demon- 

 strated, bacteria such as are capable of decompos- 

 ing rock may, in all probability, exist in the soil 

 where their activities result in the "weathering" that 

 always goes on in soils even when no organic mat- 

 ter is present. 



It has been suggested that carbon dioxid dissolved 

 in water may act on the very difficultly soluble tri- 

 calcium phosphate, producing di-calcium phosphate, 

 a more soluble form, and calcium bicarbonate, thus: 



Ca 3 (POJ 2 + 2C0 2 + 2H 2 0=Ca 2 H 2 (POJ 2 + Ca(HC0 3 ) 2 



The calcium bicarbonate thus produced, as well 

 as that derived from other sources, may then act on 

 the double silicates of aluminum and one of the alkalies, 

 thus: 



K 2 0. A1 2 3 . 6 Si0 2 + Ca(HC0 3 ) 2 = CaO. A1 2 3 . 6 Si0 2 + 2 KHC0 3 



There is then another nutrient rendered available to 

 the plant. 



It has been shown by Van Delden and by Nadson 

 that several forms (M. desulfuricans, M. cestuarii, 

 Proteus vulgaris and B. mycoides) are able to reduce 

 sulfates, while transformations of iron, silicon and 

 calcium are effected by Proteus vulgaris. 



276. Decomposition of non-nitrogenous organic 

 matter. The organic matter commonly decomposed 

 in soils contains a large proportion of compounds 



