Apr. 16,1917 
Absorption of Nutrients 
93 
obtained pretty far afield, some of these assumptions appear to be sub¬ 
stantiated by other work, the results of which it is hoped to present 
later. 
The results of the preceding work have some bearing on the law of 
minimum. The curve in figure 1, showing the percentage of the maxi¬ 
mum absorption of nitrogen attained when different percentages of the 
roots are supplied with nitrogen, has a form similar to that which 
Mitscherlich claims for the minimum curve (7, 8). The formula de¬ 
duced by Mitscherlich for the way in which plant growth increases 
with increase of the minimum factor is— 
log. (A-j)= log. (A-a)—K. x. 
x is the vegetative factor present in minimum. In our case it is the 
percentage of roots in the complete solution. 
y is the yield obtained for any value of x. In our case it is the total 
amount of the element absorbed by the plants with any portion of the 
roots in the complete solution. The amount of the element absorbed 
is expressed relative to 100, as in Table XXII. 
A is the maximum yield obtainable, under the conditions, by increase 
of x. In our case A will be the absorption attained when 100 per cent 
of the roots are in the complete solution. This is taken as 100 in each 
experiment. 
a is the yield obtaining without any addition of x. In our case a 
is obviously always O , as there can be no absorption of the element 
when no roots are supplied. 
K is a constant, “the differential factor.” 
By the substitution of the values obtained in Experiment I, as shown 
in Table XXII, the equation would be— 
log. (100-77) =log. (100-0)— K. 50 
K.— 0.0128 
By the use of the data of experiments on the absorption of nitrogen 
and phosphorus afforded by Experiments I to VI in Table XXII, the 
following values for K were obtained: 1 
0.0128 
.0111 
.0108 
.0118 
.0128 
.0128 
.0132 
.0138 
Average value, 0.0124-^0.0003 
1 The values for the absorption of potash were not used on account of the probable partial replacement 
of potash by soda. Using the data for iron absorption in Experiments IX and X, the values for K are, 
respectively, 0.0087, 0.0097, and 0.0084, average 0.0089. The fact that a different value for K was obtained 
in the experiments on iron absorption does not mean that the formula fails to hold here, but merely ex¬ 
presses the difference, already noted, between the absorption of iron and nitrogen or phosphorus. 
