332 
Journal of Agricultural Research 
Vol. XXIV, No. 4 
A special point of interest in this trial is the fact that both potassium 
nitrate and nitric acid are distinctly stimulating to plant growth at 
i,OTO parts per million. It should also be noted that their corrective 
action at i,ooo parts per million, as shown in the first and second rows 
of figure Io as well as in the third row with 5,000 parts per million car¬ 
bonate, is appreciably greater than in any of the other diagrams where 
a nontoxic concentration of an inorganic substance is used, calcium 
sulphate excepted. Accordingly, their beneficial action in this connec¬ 
tion may be due, at least in part, to an increasing of the vigor of the 
plant growth rather than to the specific reduction of the toxicity of the 
carbonate which seems to take place in cases of antagonism in solution 
cultures. Nitric acid and potassium nitrate give promise of real utility 
in correcting small and moderate toxicities of sodium carbonate in soil. 
SODIUM CHIyORID, SODIUM NITRATE, AND SODIUM SUI^PHATE 
The concentrations of the salts in this trial (fig. ii) are as follows: 
Parts per million at concentration— 
X 
9 
3 
4 
s 
NaCl.. 
700 
I, 400 
2, 100 
2, 800 
NaNOs .. 
1,000 
2, 000 
3,000 
4, 000 
5, 000 
NajSO^ . 
1,000 
3,000 
5, 000 
8, 000 
10, 000 
Na 2 C 03 . 
I, 000 
2. 000 
000 
7 . tlOO 
0, 
The salts are arranged in order of decreasing toxicity in the table. 
The results of the experiment are in agreement with the general observa¬ 
tions which have already been made on the additive toxicity of the 
carbonate. Nontoxic quantities of all the salts, particularly sodium 
sulphate, increase the yield in the presence of 5,000 parts per million 
carbonate, but 7,500 parts per million seems to be so toxic that relief is 
impossible. 
DISODIUM PHOSPHATE, SODIUM ARSENITE, AND BORAX 
These miscellaneous substances (fig. 12) were added in the following 
quantities: 
Parts per million at concentration— 
I 
9 
3 
4 
S 
Na2B407 . 
140 
280 
420 
560 
700 
NagAsOs . 
194 
388 
582 
776 
970 
Na2HP04 . 
I, 500 
3,000 
4,500 
6, 000 
7 f 500 
Na«COo. 
I, 000 
000 
t;, 000 
7, 000 
Of 
/ 7 
The borax and arsenite are 10 times as toxic as the phosphate and 
they are therefore plotted in figure 12 with one-tenth the phosphate 
scale. Under these conditions the borax and phosphate curves are 
nearly coincident, but they are somewhat higher than the arsenite curve. 
