62 
Journal of Agricultural Research 
Vd. XIV, No. i 
Using virgin soils from Riverside, California, they found ( p . 28) that 
the solubility of the potash was not— 
measurably different in distilled water and in solutions of calcium hydrate or calcium 
sulphate. 
Also in a cultivated soil from the same locality they found that the 
addition of gypsum actually decreased the solubility of the potash. 
Apparently in none of the previously reported experiments have the 
conditions of contact of the gypsum with the soil been similar to those 
which prevail in the field. In the experiments reported below, the soils, 
after having the gypsum added, were allowed to remain several months 
in a condition of moistness similar to that found under field conditions, 
which, in the case of fine-textured soils in humid regions when evapora¬ 
tion is low and plants are absent, appears to be somewhat below the 
moisture equivalent (1, p. 65). 
EXPERIMENTAL WORK 
In conducting these experiments the object was to determine-whether 
gypsum, when intimately mixed with soil and kept for some months 
under conditions of moistness similar to those prevailing in the field, 
would exert any distinct effect upon the solubility of the potash. For 
the experiment five soils (Table I), four from different parts of southern 
Minnesota and one from the Minnesota Experiment Station farm at St. 
Paul were employed. Sample A from near Wells is a fine-textured soil 
that would be classified as Fargo clay loam, according to the system of 
the Bureau of Soils of the United States Department of Agriculture. 
It is representative of a large area of poorly drained soils of lacustrine 
origin developed on the late Wisconsin glaciation, being highly calcareous 
and heavily charged with organic matter. For a soil of this texture it 
is surprisingly low in total potash. 
Tabus I .—Composition and physical properties of Minnesota soils used in the experiment 
Soil. 
Location. 
Description of soils. 
Reaction. 
Mois¬ 
ture 
equiva¬ 
Organ¬ 
ic mat- 
+ ft 
Total 
Potash. 
Calci¬ 
um 
carbon¬ 
lent. 
ated 
Per 
Per 
Per 
Wells.^ 
cent. 
cent. 
cent . 
A. 
Clay loam of lacus¬ 
Neutral. 
38-9 
8.48 
55 
4.86 
trine origin. Sur¬ 
face foot. 
B. 
Spring Valley... 
Loam from Kansan 
Acid.... 
23-8 
3-97 
i *75 
till plain. Surface 
foot. 
C. 
University 
Farm. 
Hempstead silt loam. 
Surface 6 inches. 
Acid.... 
22. O 
48.3 
1. 78 
D. 
Worthington.... 
Silt loam from late 
Neutral. 
31-2 
5 - 95 
r * 93 
•75 
Wisconsin till plain. 
Surface foot. 
E. 
Caledonia. 
Knox silt loam. Sur- 
Add.... 
* 3-5 
2. 64 
2. 25 
face foot. 
a Organic matter computed from organic carbon using the formula organic carbon X 1.724“organic 
matter. 
• Calcium carbonate computed from carbon dioxid. 
