Jan. 27, I9I9 Influence of Salts on Nitric Nitrogen in Soil 



III 



TablS II. — Percentage of nitric nitrogen formed in lOO gm. of soil containing 2 gm. 

 of dried blood and varying amounts and forms of sodium salts 



[The untreated soil is taken as loo per cent] 



Amount of sodium. 



P.p.m 



None 



3-6 



7-2 



14-4 



28.8 



57-5 



II5-0 



230.0 



460.0 



920.0 



1.380.0 



Percentage of nitric nitrogen formed in presence of — 



Sodium 

 chlorid. 



100. O 

 102. 4 



102. 5 

 100. 6 



103. I 

 114. 7 

 139.6 

 142. o 

 136. 2 



57-5 

 16. 4 



Sodium 

 sulphate. 



100. O 

 87.8 

 60.3 



57-1 

 86.2 

 74.0 

 55-1 

 65-4 

 63.2 

 63. o 

 50.8 



Sodium 

 nitrate. 



92. 

 88. 

 94. 



lOI. 



75- 

 71- 

 69. 



48. 

 17- 



— 14. o 



Sodium 



carbonate. 



100 

 100. 



79 

 76 

 88 

 94 

 79 

 73 

 76 



63 

 58 



Although sodium carbonate is toxic in the lowest concentration tested, 

 yet its toxicity does not increase as rapidly as does that of the chlorid, for 

 at the highest concentration it still produced 58.8 per cent of nitric nitro- 

 gen. The action of sulphate and carbonate nearly parallel each other 

 throughout the entire series. 



Sodium nitrate probably stimulates slightly at 28.8 p. p. m., but above 

 this concentration the nitric nitrogen rapidly decreases and when the 

 concentration of sodium in the form of sodium nitrate reaches 1,380 

 p. p. m., there is an actual loss of nitric nitrogen from the soil. 



It is quite evident from these results that the order of toxicity of these 

 salts are as follows: Sodium sulphate, sodium carbonate, sodium nitrate, 

 and sodium chlorid; but if we consider them at the highest concentra- 

 tions the order becomes sodium nitrate, sodium chlorid, sodium sulphate, 

 and sodium carbonate. 



The results for sodium chlorid confirm the findings of C. B. Lipman (<?) 

 as opposed to Deh^rain (i) that sodium chlorid does stimulate the nitri- 

 fying bacteria. Although sodium carbonate is toxic in comparatively 

 low concentrations, it is not as toxic in this soil as it was found to be in 

 the soil used by Lipman; moreover, he noted a stimulation with sodium 

 sulphate which does not appear in any of our work. This apparent dis- 

 crepancy must be due to a difference in the soils used. 



At the lower concentrations a given molecular quantity of sodium 

 sulphate is more toxic to the nitrifying organisms than is an equivalent 

 molecular proportion of sodium carbonate, and this is more toxic than 

 is an equivalent molecular proportion of sodium nitrate. Sodium 

 chlorid is less toxic than any of the other salts tested. When 4 X io~' 

 mole of sodium chlorid, sodium sulphate, or sodium carbonate are added 

 to 100 gm. of soil, the nitrate accumulation is reduced to about one-half 



