328 STATE BOARD OF AGRICULTURE. 



carbonate and non-carbonate soils closely correlated with the quantities 

 of calcium found in the soil solutions. (5) The fixation of potassium from 

 KCl also correlated somewhat with the quantities of calcium and Si02 

 dissolved from the non-carbonate soils by 0.2 N HCl. (6) Except in two 

 cases, soils No. 20 and 23 with KCl treatment, all the solutions were alkaline 

 to red litmus paper. (7) Iron and aluminum were undoubtedly present in 

 many of the solutions but no evidence was found that these elements were 

 combined with the anions of the neutral salts used. (8) Potassium and sodium 

 probably played an unimportant part in the experiments performed on soils 

 not previously treated with salts of these elements. (9) The alkaline soils 

 generally fixed a greater quantity of cation than the acid soils of the same 

 class, but it was shown that the degree of fixation depended upon certain soil 

 elements, chiefly calcium and magnesium in a condition to react with the 

 neutral salt and not on the reaction of the soils. (10) Extracting the eight 

 soils with HCl and washing thoroughly greatly reduced the quantities of 

 potassium fixed from KCl. (11) Potassium, calcium and magnesium were 

 not fixed from neutral salts by the eight soils in equivalent quantities, 

 showing that in each case fixation depended on different soil factors. (12) 

 The fixation of potassium correlated with the exchange of calcium and mag- 

 nesium; the fixation of calcium with exchange of magnesium; and the fix- 

 ation of magnesium with exchange of calcium. (13) The reactions were 

 reversible in all cases studied. (14) When the alkaline and acid sandy loam 

 soils were saturated with certain cations at equal solution concentrations, 

 then the fixation of the other cations used at the same concentrations was 

 closely equivalent. These observations contain strong proof that the reac- 

 tions involved are chemical in nature and that the cause of fixation by soils 

 is the presence of soil elements, principally calcium and magnesium in a con- 

 dition of reactivity, and the degree of fixation is independent upon both the 

 kind and quality of reacting elements present. 



In general the results of this investigation agree with the chemical hypo- 

 thesis established by Way (9, 10). They also give a logical basis for the 

 explanation of: 



(1) Why the fixation capacities of soils of the same class often vary con- 

 siderably, while the capacities of unlike classes may be similar. (2) Why 

 a soil exhibits a certain degree of selection in this respect, that is, certain 

 cations are fixed in greater quantities than others. (3) Why the order of 

 fixation of several cations may vary in different soils. (4) Why mixture of 

 neutral salts give varying effects on the same soil. (5) Why the degree of 

 fixation correlates quite closely with the general fertility condition of soils. 

 (6) Why leaching soils with acids decreases the quantity of fixation. (7) Why 

 liming the soil increases the quantity of fixation. (8) Why the anions of neu- 

 tral salts that form soluble compounds with calcium or magnesium are not 

 fixed by soils, and (9) why the anions or acid radicals of salts that form insol- 

 uble compounds with soil calcium or magnesium are fixed by soils — phenom- 

 ena observed by many soil investigators. 



A prominent feature of this research was that very small quantities of 

 potassium or sodium were found in soil solutions from untreated soils ex- 

 amined for these elements. The natural conclusion from these results was 

 that these elements do not occur in appreciable quantities in replaceable 

 combinations in the soils studied. Granting this conclusion to be true, a 

 possible explanation may be given on the bais of the differences in solubilities 

 of the carbonates of the alkali earth elements. Hydration and carbonation 



