EXPERIMENT STATION BULLETINS. 335 



calcium than the other member of its class, and liberates more calcium but 

 less magnesium. The fixation of potassium from KC2H3O2 by the clay- 

 loam soils does not agree with the above explanation although the results 

 are in close agreement. The acid silt loam fixed more PO4 from Ca(H2P04)2 

 than did the alkaline silt loam. The effects of the presence of CaCOa in the 

 alkaline medium sand was also noticeable in case of the calcium salts and 

 FeCls treatments. The dissimilar effects noted between hydrolyzing and 

 neutral salts treatments were a much greater quantity of potassium fixed 

 from the hydrolyzing salts, and the absence of chemical equivalents between 

 elements fixed and those found in the soil solutions. The hydrolyzing salts 

 used may be placed into three separate classes based on their effects upon the 

 soils; namely, alkahne salts, acid salts and salts forming insoluble compounds 

 between their acid radicals and soil elements. A fourth class may be con- 

 sidered in cases where an acid radical of an acid hydrolyzing salt would 

 form an insoluble compound with soil elements. 



A brief summary of observed effects of the hydrolyzing salts treatments 

 follows: (1) The alkaline soils, with few exceptions, fixed a greater quantity 

 of cations from hydrolyzing salts than the acid soils of the same classes. 

 (2) Greater quantities of cations were fixed from hydrolyzing salts than from 

 neutral salts. (3) Closely equivalent exchanges of soil elements for those 

 fixed from hydrolyzing salts were not observed, however, the fixation of iron 

 from FeCls was nearly proportional to the calcium found in the soil solutions 

 except in case of the limed soil. (4) Exchange of soil elements was observed 

 in cases where these elements formed soluble compounds with the anions 

 of the salts used. (5) Fixation of one ion of a hydrolyzing alkaline salt was 

 apparently independent of the fixation or combination of the others. 



GHNIBRAL SUMMAIRY 



Data accumulated in this research point strongly to the conclusion that 

 when neutral salts, hydrolyzing salts or hydroxides in solution are placed 

 in contact with soils a chemical reaction results in which portions of the 

 cations or basic radicals of the added compounds are precipitated in the 

 soil mass and in case the anions or acid radicals of the salts used form soluble 

 compounds with calcium or magnesium the resulting salts are found in the 

 soil solution. When the acid radicals of added salts form insoluble compounds 

 with calcium or magnesium they were also precipitated in the soil. Fixa- 

 tion or precipitation of potassium, sodium and ammonia ions from neutral 

 salts was shown to be dependent chiefly upon the calcium and magnesium 

 of the soils, while the fixation of calcium depended upon soil magnesium and 

 fixation of magnesium upon soil calcium. The several classes of components 

 used in treating the soils, however, showed different effects. With few ex- 

 ceptions the alkaline soils fixed greater quantities of the members of the 

 salts fixed than the acid soils of the corresponding classes. 



The reaction between neutral salts and soils appeared to be less compli- 

 cated than in case of any of the other classes of compounds used. A portion 

 of the cations of the salts used was precipitated in the soil mass and a nearly 

 equivalent quantity of certain soil elements, or a soil element depending 

 upon the salt used, combined with the anion of the salt was found in the 

 resulting solutions. The cations precipitated or fixed were replaced by dis- 

 similar cations of neutral salts which were also fixed in the soils. 



Cations of the bases used were probably fixed in the soils without exchange 

 of soil elements, because the quantities of calcium found in the solutions from 



