1910] SCHREINER & SKINNER—ORGANIC SOIL CONSTITUENT 177 
which is shown when this substance is present for a proportionately, 
and sometimes even absolutely, greater decrease in the nitrogen of 
the solutions, is strikingly shown in this first period (fig. 9). This 
varies somewhat from period to period; thus, for instance, in the 
fourth period, shown in fig. 10, the ratio change is fairly normal, 
though the usual tendency is seen again in the seventh period, a: 
P205 
\ Ih 
———_—— 
K0 ~ ee ag 
Fic. 10.—Showing the ratio of the original, the final, and the ratio of the loss of 
P.0;, NH;, and K,O from the solution, in the fourth period 
diagram of which is presented in fig. 11. These diagrams for the 
several periods illustrate rather well the general tendencies brought 
out by an examination of the analytical data. As a rule, beyond 
the second or perhaps the third period the diagrammatic representa- 
tion of the result is on the whole uniform, but is influenced undoubt- 
edly by the conditions of growth during any period; in other words, 
by weather and other conditions, which is shown perhaps quickest 
