Jan. 27. 1919 Influence of Salts on Nitric Nitrogen i?i Soil 121 



In a later report {13, p. 196-202) he shows that the percentage of 

 phosphorus in a plant is increased by the use of a sodium salt. With 

 radish this was in some cases as much as 0.052 per cent more in the crop 

 from land which had received a full ration of sodium over that which 

 received but a part ration. In the case of turnips there was a difference 

 of 0.12 1 per cent, the beets 0.035 per cent, the carrots 0.074 per cent, 

 while in the case of the chicory the results are practically the same in 

 the crop from the manured and unmanured land. The report contains 

 many more cases in which the sodium salt increased the phosphorus in 

 the plant. However, the laboratory tests which have been made on 

 phosphates show that sodium chlorid depresses the solubility of a phos. 

 phate (2). 



It is therefore evident from the results obtained that sodium chlorid 

 increases the ammonia and nitric-nitrogen accumulation of the soil, and 

 all indications point to the conclusion that this is due to an increased 

 activity of bacteria, which bring about this transformation. This being 

 the case, there must be an increase of the nitrites produced in the soil by 

 nitrosomonas, and Hopkins and Whiting (7) have demonstrated that 

 these organisms possess the power of rendering soluble the phosphorus 

 of the soil. Therefore we could expect to find an increased yield when 

 sodium chlorid is added to a soil deficient in soluble phosphate but con- 

 taining considerable insoluble phosphate, this increase being due to the 

 liberation of phosphorus, which we find reveahng itself in a greater phos- 

 phorus content of the plants, as noted in the above references. 



The concentration at which the various compounds are found to exert 

 their greatest stimulating action varies greatly with the compound. The 

 maximum for the different compounds is as follows: Calcium chlorid 

 709.2 p. p. m., chlorin as sodium chlorid 354.6 p. p. m., chlorin as ferric 

 chlorid 88.7 p. p. m., chlorin as magnesium chlorid 117.3 p. p. m., chlorin 

 as manganous chlorid ii.i p. p. m., chlorin as potassium chlorid 22.2 

 p. p. m. 



The point at which the specific compound becomes toxic varies greatly 

 with the cation. With the exception of calcium chlorid there is nearly 

 the same quantity of nitric nitrogen in all soils at the highest concentra- 

 tion, 2,127.6 p. p. m. of chlorin in the various combinations. 



The difference in toxicity of the compounds becomes greater when we 

 compare equal molecular portions of the different compounds, as may be 

 seen from Table XL 



