39 



and others, and will not be taken up here. SufYice it 

 to say that the results obtained by various experi- 

 menters are quite contlicting; some obtaining bene- 

 ficial results, others negative results, and still others 

 injury. Most workers are agreed, however, that appli- 

 cation of soluble manganese compounds in amounts 

 much greater than 50 pounds per acre are likely to 

 cause injury, even where smaller amounts have pro- 

 duced increased yields. 



With regard to the presence of water soluble manga- 

 nese in soils, Kelly and McGeorge (9) report the analy- 

 sis of 12 Hawaiian soils representing a very wide range, 

 including normal and abnormal types. Of the 12 soils 

 studied, 3 had more than 20 p. p. m. of soluble Mn:.04, 

 while only two had less than 5 p. p. m. Drying these 

 soils at 100' C. increased the solubility of manganese in 

 9 of the 12 soils; and drying at 250" C. produced an in- 

 crease in 11 of the 12 samples. The maximum solu- 

 bilities in the soils dried at 100' C. were 161.1 and 180.5 

 p. p. m. respectively. 



In an unproductive soil on which legumes failed, 

 Newell (13) found considerable quantities of manga- 

 nese comi)ounds soluble in water. Examinations of 

 the extracts made from this soil showed that it contain- 

 ed about twice as much manganese as calcium, and it 

 was suggested that the occurrence of such compounds 

 contributed largely to the sterility of this soil. 



De Sornay (4) states that Boname found that the ni- 

 tric acid formed through nitrification, combined in the 

 absence of a base, with manganese. While DeSorna^^'s 

 own work showed a considerable solubility of manga- 

 nese in 2 per cent nitric acid, not more than a trace 

 of manganese was dissolved by water, using the same 

 methods of extraction in each case. 



In a discussion of the effect of manganese phosphate 

 on plants, Truog (20) states that "water extracts of 

 acid soils often contain considerable amounts of man- 

 ganese. When these soils are limed, scarcely no manga- 

 nese is found in the w^ater extract. Since manganese 

 may greatly affect chloroph^dl formation especially of 

 clover and alfalfa, it seems possible that in some cases 

 one of the reasons why soil acidity is injurious to clov- 

 er and alfalfa is the presence of considerable manga- 

 nese in the soil solution and hence in a condition to 

 enter the plants in considerable amounts. The varia- 

 ble deportment of manganese in its chemistry makes it 



