58 
Journal of Agricultural Research 
Voi. XXIII, No. 2 
of the two series was not taken, as the purpose of the work was to demon¬ 
strate tendencies rather than to obtain absolute figures. 
The plots comprised i square rod each, with 2-foot alleys between them. 
principles underlying selection op chemicals 
When flinty wheat kernels were soaked in the laboratory in a slightly 
acid solution they lost their brown color, and when yellow-berried kernels 
were soaked in a slightly alkaline solution they acquired the brown col¬ 
oration characteristic of flinty grain. This suggested the idea that the 
color characteristics of flinty and yellow-berried grain constitute indica¬ 
tor reactions with alkalies and acids, as well as the possibility that the 
elimination of yellow-berry caused by the application of sodium nitrate 
was due to the residual effect of the sodium base. 
The nitrogen carriers used in this experiment were accordingly of 
two distinct groups: Nitric acid and its salts and ammonia and its salts. 
The salts of the nitric acid belong to the physiologically alkaline group. 
Since the plants use the nitrogen of the acid radicles more readily than 
that of the basic elements, residues of basic radicles are left. Following 
the same reasoning, the salts of ammonia may be placed in the physio¬ 
logically acid group. Ammonium nitrate is a physiologically neutral 
salt. Nitric acid would have the status of a nitrate, since it attacks the 
physiologically neutral salts of the soil, particularly the carbonates, 
thus being transformed into a physiologically alkaline substance. Am¬ 
monia, which nitrifies very readily, would have approximately the same 
status as nitric acid. The status of potassium nitrate would depend 
upon the rate of assimilation of potassium and nitrogen by the plants, 
which would vary w r ith soil conditions. If these two elements were 
assimilated by the plants at the same rate, the status of potassium nitrate 
would be that of a physiologically neutral substance. Should these two 
elements be assimilated at different rates, its status would always be that 
of a physiologically alkaline substance. Should nitrogen be assimilated 
mote readily, a residue of basic potassium would be the result. On the 
other hand, should potassium be assimilated more readily, the residue 
would be nitric acid which, as just explained, would act as a physio¬ 
logically alkaline substance. 
The same principle underlies the selection of the other chemicals. It 
was expected that the acids and alkalies w r ould produce direct effects 
of alkalinity and acidity. The salts of potassium were counted on to 
produce physiological acidity. The physiologically neutral salts were 
intended to serve as controls with reference to the residual acid and basic 
radicles of the nitrogen carriers. 
The term “residual effect'' is used in this connection to signify the 
possible effect of residual acid or basic radicles on the soil reaction, as 
well as their effect on the physiological reaction of the plant tissues. 
FACTORS WHICH TENDED TO DISTURB THE REGULARITY OF RESULTS 
The plots were laid out in the spring just before the first application. 
Due to the fact that the wheat in Nebraska in that year suffered heavily 
from late frosts, it was impossible to obtain uniform plots. The part of 
the field used for series A was fairly uniform, and the plots were laid out 
consecutively. The section of the field which was available for series B 
was entirely lacking in uniformity. An attempt was made to select fairly 
