EXPERIMENT STATION BULLETINS. 



675 



slow, SO slow indeed that it requires months, at least with certain min- 

 erals to form a saturated solution. Many if not all of the common soil- 

 forming minerals, however, undergo hydrolj'sis and thereby increase 

 their degree and rate of solubility. Their solubility may be further in- 

 creased by the addition of soluble compounds yielding non-common ions, 

 or by their reacting with some of the minerals to form new compounds, 

 or by the dissolved components of the different minerals acting upon one 

 another to form new compounds. Finally, the reduction of the soil 

 particles into finer division both by climatic weathering and by artificial 

 management increases the amount of material that goes into solution 



Through these processes of hydrolysis, chemical reaction between ap- 

 plied salts and soil minerals, the reaction of the dissolved components 

 of the different minerals, etc., probably there are formed in the soil solu- 

 tion 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, SiOs, etc., and the base radicals Na, Mg, Ca, K, Al, Fe, etc. 

 These acids and bases could well combine to form such compounds, for 

 instance, as CaH,(POJ„ Na„HrO„ K.HPOi,, NaHCO,, MgCHCOJj, 

 CaSO,, Na,SO„ NaCl, KCl, CaCl^, Ah{1^0,):„ AICI3, Al^CSOJa, Fe- 

 (NOa),, FeCL, FeSO,, etc. 



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

 or less extent can hardly be doubted. Both direct and indirect evidences 

 strongly support the assumption. For instance, in those regions where 

 the rainfall is small and the amount of leaching is consequently slight, 

 such as in the arid regions, there is an accumulation of soluble salts 

 near or at the surface of the soil, transported from below by the evapora- 

 tion of the soil water. Such an accumulation of salts is designated as 

 alkali conditions. Similar alkali conditions would doubtless 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. Table 6 which has been prepared by 

 Lyon, Fippin, and Buckman (7), shows the kind and percentage compo- 

 sition of alkali salts in soils. 



(') Lyon, Fippin and Buckman. Soils, Their Properties and Management, p. 393, 1915. 



