330 
Journal of Agricultural Research 
Vol. XXIV. No. 4 
It should be particularly noted that the addition of nontoxic amounts 
of sulphates (up to 3,000 to 5,000 parts per million) to the soil containing 
appreciably harmful concentrations of carbonate almost invariably 
causes the growth of the plants to be somewhat better than with the 
carbonate alone. Three exceptions to this rule appear when sodium 
sulphate alone and also two mixtures of this salt with potassium sulphate 
are added to the most toxic black alkali soil. A distinct corrective action 
or antagonism for sodium carbonate is thus indicated, since no marked 
stimulation or corrective action is apparent when these substances are 
added to the untreated soil or to the practically nontoxic carbonate soils. 
HYDROCHLORIC ACID, POTASSIUM CHLORID, AND SODIUM CHLORID 
The concentrations used in this trial (fig. 9) are as follows: 
Parts per million at concentration— 
z 
9 
3 
4 
5 
HCl. 
800 
1,000 
700 
1,000 
1,600 
2, 000 
1,400 
3,000 
2, 400 
3,000 
2, 100 
5,000 
3,200 
4,000 
2, 800 
7,000 
4,000 
5,000 
3, 500 
KCl... 
NaCl. 
NaoCd.. 
The order of increasing toxicity of these substances is potassium 
chlorid, sodium chlorid, and hydrochloric acid. This order is maintained 
quite consistently throughout all the mixtures in the trial. The acid 
probably exerts its harmful properties through being changed to calcium 
chlorid. This salt is nearly as toxic as sodium chlorid, weight for weight, 
and the deficiency is more than made up by the fact that two parts of 
acid produce three parts of calcium chlorid. 
It is to be noted again that sodium carbonate at 3,000, 5,000, and 7,000 
parts per million lowers the yield of the single chlorid treatments by its 
own toxicity. A slight correction of the harmful effects of both 5,000 
and 7,000 parts per ^lion of the carbonate has been brought about by 
the lowest concentrations of the chlorids; but this was very slight indeed 
in the former case, due to the fact that the sodium carbonate was less 
harmful than usual in this instance. 
NITRIC ACID, POTASSIUM NITRATE, AND SODIUM NITRATE 
This treatment (fig. 10) contains the following concentrations: 
Parts per million at concentration— 
z 
9 
3 
4 
5 
HN03. 
I, 000 
2, 000 
3,000 
4,000 
5,000 
KN03. 
I, 000 
2, 000 
3,000 
4, 000 
5,000 
NaN03 . 
I, 000 
2, 000 
3, 000 
4, 000 
5,000 
Na..CO«. 
I, 000 
000 
5, 000 
7, 000 
