1917] Lipman-Gericlce : Smelter Wastes and Barley Growth 549 



the salts here under discussion are to be accounted for by their 

 effects on the nitrifying flora and hence on the available nitrogen 

 supply, we do believe that the latter is one of the few important 

 factors — perhaps the most important — involved in the problem 

 of explaining stimulation of plants in soils particularh", and 

 possibly also, to some extent, the toxicity of salts in soils. That 

 the effects of the salts on the nitrifying powers of the soils here 

 studied are not the exclusive cause of the phenomena above dis- 

 cussed, we can probably believe with confidence. The total 

 quantities of citric acid-soluble phosphoric acid and potash in 

 soils have been found by us to be augmented through the action 

 of the metallic sulfates in question, and we are also aware of 

 the possible inhibiting effects of those salts for certain factors 

 which may be inimical to the proper development of the soil 

 bacteria. 



In addition, there can be no question about the profundity 

 of the changes in the soil's physical condition induced by any 

 metallic sulfate and about the effects which follow in its wake. 

 Most notable of all facts in that connection is the fluffy and 

 pulverulent condition of the soils treated with ferrous sulfate, 

 due undoubtedly to the formation of hydrated ferric oxide and 

 other similar compounds. Special studies (unpublished) carried 

 out by Mr. H. H. Coolidge on the soils of the ferrous-sulfate 

 series, showed that the treatment of the soil reduced its power 

 to raise water to a certain point, while at first allowing it to raise 

 it faster ; that the hygroscopicity of the soil was reduced ; that 

 its total water-holding power and its water-retentiveness were 

 diminished; that its percolation power was increased; that its 

 moisture-equivalent was diminished. Mr. Coolidge also found 

 that, contrary to the effects of CuSO^ and some of the other 

 sulfates, the soil's water-soluble phosphorus and potassium were 

 very much reduced in quantity by treatment with FeS04. Dif- 

 ferent and numerous though these effects be, there can be little 

 question that they must influence, to some degree at least, the 

 soil's nitrifying power. A further discussion of this phase of 

 the problem is, however, impossible at this time and must await 

 consideration in connection with some of our other studies. 



