ACTION OF MANGANESE IN SOILS. 



13 



Table III. — Effect of manganese (50 parts per million) on growth and oxidation in 

 extracts of a poor sandy loam soil. ( Untreated extract taken as 100.) 



Treatment. 



Relative 

 oxidation. 



Extract untreated. . 



Extract+MnCl 2 



Extract+MnS0 4 . . . 

 Extract+Mn(N0 3 ) 2 

 Extract+MnC0 3 . . . 



100 

 116 

 140 

 200 

 196 



There was an increased oxidation power of the plant roots in the 

 manganese cultures. Each of the salts caused an increase in oxida- 

 tion and also an increase in the growth. The manganese chloride 

 increased oxidation 16 per cent and growth 14 per cent. The sulphate 

 increased oxidation 40 per cent and growth 16 per cent. The nitrate 

 increased oxidation 100 per cent and growth 8 per cent. The car- 

 bonate increased oxidation 96 per cent and growth 11 per cent. It 

 should here be noted in connection with the last two compounds that 

 root oxidation is also greatly increased by nitrates and by alkaline 

 conditions, as shown by Schreiner and Reed. 1 The high oxidation 

 here noted is therefore the summation of the effects of manganese and 

 nitrate or carbonate, respectively. 



The greatest amount of oxidation in the solutions containing the 

 different salts of manganese does not give the largest increase in 

 growth. This suggests that the oxidation in the solutions contain- 

 ing the nitrate and carbonate in the amounts of 50 parts per million 

 was perhaps too great for the best growth in this culture medium. 



Another experiment with this soil extract was made using several 

 concentrations of manganese sulphate, namely, 10, 30, and 50 parts 

 per million. Two cultures were run in each treatment. The experi- 

 ment continued from February 9 to February 19. .The results are 

 given in Table IV. 



Table IV. 



-Effect of manganese sulphate on oxidation and growth of wheat in extracts 

 of a poor sandy loam. ( Untreated taken as 100.) 



Treatment. 



Relative 

 oxidation. 



Extract untreated 



Extract + manganese 10 parts per million. 

 Extract + manganese 30 parts per million. 

 Extract + manganese 50 parts per million. 



100 

 133 

 173 

 210 



As seen in the table, the oxidation and growth increased as the 

 amount of manganese in the solution increased. This experiment 

 was repeated, the plants growing from February 25 to March 13. 

 The results were very similar to those in the first test. With 10 parts 

 per million, manganese oxidation was increased 35 per cent and 



i Bui. 56, Bureau of Soils, U. S. Dept. Agr. 



