864 Journal of Agricultural Research voi.xx, No.n 



Of the 34 soils represented in Table III, 13 required less calcium 

 hydroxid for the titration of the subsoil than for the surface soil. Eight 

 of these 13 soils have over three times as much calcium in the subsoil 

 as in the surface soil. From the figures presented in Tables I and II, 

 it is shown that when a soil has large amounts of calcium, especially in 

 the carbonate form, the amount of calcium hydroxid used to bring to a 

 certain reaction was less than when the calcium content was smaller. 

 That is shown by comparisons of the groups. A large amount of calcium 

 has a greater influence than a larger amount of clay. 



The result on soil No. 1273 can be explained by the lesser clay content 

 of the subsoil, as was pointed out in a preceding paragraph. 



The following four soils have only slightly more calcium in the subsoil, 

 and yet they require less calcium hydroxid for the subsoil than for the 

 surface soil: 



1 199.3, Laurel very fine sandy loam. 



1 162.3, Pratt fine sandy loam. 



1 12 1. 3, Finney clay. 



1287.3, Summit silty clay loam. 



The results on the first two may be explained by the lesser clay con- 

 tent of the subsoil. Finney clay 11 21.3 is an abnormal soil. The 

 sample was taken from the edge of a buffalo wallow. The probability 

 is that the surface soil had more colloidal clay than the subsoil. 

 Sample 1687 must be an exception; no explanation is apparant. 



The foregoing presentation shows that most subsoils have a greater 

 calcium content than the surface soil and also that the subsoils require 

 a larger amount of calcium hydroxid to bring to the same reaction as the 

 surface soil. This must be due to the absorptive power of the colloidal 

 clay. It can not be due to a larger acid content or to a deficiency of 

 basic elements. The larger content of calcium should neutralize the 

 acidity, and since the calcium content is larger in the subsoil than in 

 the surface soil in can not very well be said than the subsoil is more de- 

 ficient in lime. 



The initial reaction of a soil is not necessarily an indication of the 

 amount of calcium hydroxid required to titrate to a given hydroxyl-ion 

 concentration. In Table II the results are arranged according to the 

 decreasing hydroxyl-ion concentration of the soil before titration. If 

 these figures are studied in comparison with the figures in Table I it is 

 found that the amounts used to titrate do not correspond to the initial 

 reaction nor to the content of calcium except in the following general way. 

 The soils placed in group I have a larger calcium content than the soils in 

 group II, and those in group II have a larger calcium content than those in 

 group III. The quantities of calcium hydroxid used in titration are 

 greater for soils in group III than for soils in group II, and greater for 

 those in group II than for those in group I. But for individual soils 

 this comparison does not hold. 



