38 



from the high nitrate soil gave quite a precipitate with 

 hydroxides. 



This work was actively resumed in the fall of 1916. 

 On Octoher 21, the plots were prepared and fertilized 

 as usual, a part of the fertilized plots again being cov- 

 ered to protect them from rainfall. The characteris- 

 tic brown crust again appeared on the surface beneath 

 the covers; and during a rather long rainless period 

 the entire surface of some of the plots showed the 

 brown incrustation. From this crusted surface, a bulk 

 supply of soil was collected and taken to the labora- 

 tory for a study of the water soluble constituents there- 

 in. Continuing the work which had been started in 

 the spring, water extracts of the high nitrate soil were 

 analyzed, and were found to contain but little chlo- 

 rides or sulphates, but enormous amounts of nitrates. 

 Iron and aluminum were present in mere traces, or 

 absent; but in every instance where the nitrate con- 

 tent of the soil was high, a large amount of manganese 

 was found. On the contrary, in no case was a large 

 amount of soluble manganese found in the soil from 

 these plots, if the nitrate content was low. It was appar- 

 ent, then, that there was some correlation between ni- 

 trate production and the development of soluble man- 

 ganese in this acid soil. And since soluble manganese in 

 appreciable quantities is toxic to plants, it was appar- 

 ent, further, that it was the soluble manganese that was 

 causing the injury to corn and sorghum in the pot 

 experiments before mentioned. 



It is the aim of this paper to report the work done 

 in the effort to show whether or not soluble manganese 

 is the caugc of injury to plants grown in these soils, 

 and if the process of nitrification is the cause of the 

 development of soluble manganese. 



Review of Literature 



A search through the literature shows that, while a 

 large amount of work has been done with soluble man- 

 ganese salts added to soils, but little study has been 

 made of the water soluble compounds of manganese 

 normally appearing in soils. Heretofore, the studies 

 have been nuidc chiefly on the assumption that there 

 was a deficiency of such soluble compounds, and that, 

 by their application, plant growth might be increased. 

 Reviews of the literature bearing on this phase of the 

 subject have been made by Kelley (8),* Skinner (18), 



(*) Reference is made by No. lo "Literature Cited" P. 41. 



