Jan. i S , 1917 
Calcium Compounds in Soils 
77 
It should be noted that both these types are described as having poor 
drainage, a condition nearly always found when acid soils occur. 
Two other soil types represented, Clyde silty clay and Crosby silty clay 
loam are characterized by poor drainage, but are not acid to litmus. 
Both are derived from highly calcareous material, and the sample of the 
lower subsoil of Crosby is really the till from which the soil was derived. 
The total calcium content of both is fairly high, and the Clyde samples 
are characterized by a high content of easily decomposable silicates. It 
is conceivable that easily decomposable silicates might bring about the 
neutralization of acids being slowly formed in a soil in much the same 
way that calcium carbonate does. 
Another point in connection with soil acidity and the presence of cal¬ 
cium carbonate in soils is the relation of the growing of legumes to these 
two factors. It seems to be well established that acid conditions are 
generally unfavorable or even disastrous to such crops, and from this it 
is assumed that the presence of calcium carbonate is necessary. The 
data discussed in this paper, while not such as to furnish any basis for a 
discussion of the subject, are in one particular suggestive. The Meck¬ 
lenburg clay loam is recognized as a good alfalfa soil. It is high in total 
calcium content with almost negligible quantities of calcium carbonate. 
In conclusion it should be stated that the method by which the results 
presented have been obtained is put forward as a tentative one and with 
a full realization of its shortcomings. It is hoped to make this method, 
or some method of determining the forms of calcium in soils, more com¬ 
prehensive and less open to objection. 
SUMMARY 
In this paper there are presented analytical data bearing on the kinds 
of calcium compounds in 63 samples of soil representing 23 types from 24 
locations in 19 States. 
From these analytical data the quantities of calcium carbonate, calcium 
sulphate, calcium combined with humus compounds, and calcium present 
as easily and difficultly decomposable silicates have been calculated. 
The figures obtained show a wide variation in total calcium content 
and in content of calcium carbonate and the two classes of silicates. 
Calcium combined with humus compounds is shown to be absent in 29 
samples. 
No relation is apparent between the total calcium content and the 
quantity of any of the classes of calcium compounds discussed. 
It is shown that it is possible to have two soils with the same calcium 
content, but with the kinds of calcium compounds present in quite dif¬ 
ferent quantities. 
But five of the samples, representing two types, were acid to litmus. 
These types are characterized by poor drainage. 
A type represented in this series recognized as a good alfalfa soil is 
characterized by a high calcium content, but low in content of calcium 
carbonate. 
