572 
Journal of Agricultural Research 
Vol. XXI, No. 8 
one element combined with one solution lacking one element, agree more 
closely than the values for any one combination of specific solutions. 
This is because the method of calculation does not take into account 
certain less important factors, such as the apparent greater need of the 
plant for nitrogen than for phosphorus or potassium. 
Table XIX .—Actual and calculated values of mean assimilations of nitrogen (N), 
phosphoric acid (P 2 0 5 ), and potash ( K 2 0) 
Solution. 
B flasks. 
C flasks. 
NK. 
NP. 
NK. 
N. 
K. 
P. 
NK. 
NP. 
PK........ 
N. 
PK. 
K. 
NK. 
P. 
P. 
N. 
N . 
P. 
K. 
P. 
P. 
K. 
Mean assimilation of nitrogcn(N), phosphoric acid (PsOs), 
and potash (K2O) relative to the normal taken as 100.“ 
Actual 
value. 
Average of 
actual values 
for similar 
combinations 
of solutions. 
35 
| 
59 
58 
79 
J 
37 
1 
57 
\ 44 
37 
J 
68 
38 
3 i 
40 
52 
23 
33 
31 
38 
i 5 
A flasks. 
PK.. 
PK.. 
NP.. 
PK.. 
NP.. 
NK. 
PK. 
NK. 
NP.. 
NP.. 
NK. 
PK.. 
NP.. 
N. . . 
Average. 
43 
Calculated 
values. 
5 2 
52 
54 
3 6 
42 
42 
57 
40 
46 
46 
30 
3 1 
34 
21 
Average of 
calculated 
values for 
similar com¬ 
binations of 
solutions. 
53 
40 
44 
32 
42 
o The normal assimilation is that of the control plants grown with all their roots in the complete solution. 
It is interesting to note that the way growth and assimilation diminish 
with increasing localization of different nutrients does not follow the law 
of minimum. According to any one of the formulations of the law of 
minimum, growth is not much less when three elements are equally 
deficient than when only one element is deficient. However, there are 
many experimental deviations from the law as usually formulated, and 
these results suggest an explanation for some of the apparent exceptions. 
The fact that in this work the ratio of roots to tops increased as assimi¬ 
lation diminished may mean simply that a reduced assimilation of nutri¬ 
ents depresses the growth of roots less than it does the growth of tops. 
It may be, however, that a diminished assimilation of nutrients is directly 
stimulating to root growth. The growth of roots depends, of course, 
among other things, on the amount of organic material transported from 
the tops. Whether organic compounds are transferred to different parts 
of the leaves and stalks or to the roots may well be governed in part by 
the rate nutrient ions are utilized in the tops. When utilization is slow, 
