612 STATE BOARD OF AGRICULTURE. 



diluted, nnd. as tlip jx^rcentpic of waier is reduced, it heroines more con- 

 centrated; lience, the luwerin<»- of the freezing point would tend to in 

 crease from the liigh to the low Avater content. 



The dissolution of Ihe mineral matter is accomplished by the solvent 

 action of water aided by the foreign f^ubstances that it might ))e charged 

 with, such as acids, bases, and salts. The soil minerals, however, arc 

 as a rule but slightly soluble and their rale of solution is generally 

 very slow, so slow indeed that it requires months and even years, at 

 least with certain minerals, to form a saturated solution. Thus, Cam- 

 eron and Bell, (12), found that by placing powdered glass, orthoclase, 

 albite, and some Podunk fine sandy loam with water in paraffin cylinders 

 and rotating them in a constant temperature bath at 27°C tor about 

 9 weeks, equilibrium was not yet attained. Manj^ if not all of the com- 

 mon soil forming materials, however, undergo hydrolysis and thereby in- 

 crease their degree and rate of solubility. Their solubility may be further 

 increased by the addition of soluble compounds yielding non-common 

 ions, or by the reacting with some of the minerals to form new com- 

 pounds, or by the dissolved components of the different minerals acting 

 upon one another to form new compounds. 



Through these processes of hydrolysis, chemical reaction between ap- 

 plied salt and soil mineral, and the reaction of the dissolved components 

 of the different minerals, probably there are formed in the soil solution, 

 salts of high solubility. 



In the analysis of soil water extracts, drainage waters, etc, there 

 are found, besides the NO3 acid radical, the acid radicals HPO4, SO4, 

 HCO3, CI, SiOo, and the base radicals, Na, Mg, Ca, K, etc. These acids 

 and bases could well combine to form such compounds, for instance, as 

 CaH,(PO,)o, Na,HPO„ K^HPO,, NaHCOs, Mg(HC03)„ CaSO,, Na,: 

 SO,, NaCl, KCl, CaCl^, etc. 



That such compounds are formed and do exist in the soil solution to 

 a more or less extent, can hardly be doubted. Both direct and indirect 

 evidences strongly support the assmiiption. For instance, in those 

 regions where the rainfall is small and the amount of leaching is con- 

 sequently slight, sucli as in the arid regions, there is an accumulation 

 of soluble salts near or at the surface soil, transported from below by 

 the evaporation of the soil water. Such an accumulation of salts is 

 designated as alkali conditions. Such alkali conditions would occur 

 even in the humid regions were it not for the excessive and frequent 

 rains which tend to wash away these soluble salts and thus prevent 

 their accumulation. The soluble salts found wherever alkali conditions 

 exist vary in number and composition, but in most arid countries the 

 chlorides, sulphates, and carbonates of sodium, calcium, and magnesium, 

 predominate. Several other salts are generally found but not in large 

 amounts. In humid regions there are many cases known where seem- 

 ingly alkali conditions exist. Cameron, (11) reports that a soil in 

 Maryland near the Maryland Agricultural College contained the follow- 

 ing salts in large quantities: NaN03, KNO3, Mg(N03)2, Ca(N03)2, 



(") Bui. 30, Bureau of Soils, U. S. Dept. of Agr., 1905. 



(») Bui. 17, Bureau of Soils, U. S. Dept. of Agr., p. 36,^1901. 



