32 BULLETIN" 42, U. S. DEPARTMENT OF AGRICULTURE. 



oxidation was tested after the plants had been growing for two weeks. 

 The effect of manganese on the oxidizing power of the plant roots and 

 on growth gave different results with different soils. 



With poor, unproductive soils manganese salts increased oxidation 

 and growth. This was especially true in extremely poor soils and in 

 a soil in which were found several harmful organic compounds. 



Some harmful soil constituents themselves check the oxidizing 

 power of plant roots, and their harmfulness is overcome by fertilizers 

 which stimulate oxidation. 



Oxidation was increased in productive soils; the growth, however, 

 was decreased. The plants snowed indications of excessive oxida- 

 tion. As the oxidation processes in these soils were already good, 

 the harmful action is attributed to excessive oxidation. 



The beneficial action of manganese may be due to its function of 

 aiding and increasing the oxidation processes and other vital proc- 

 esses in the plant as well as in the soil, and by this means changing 

 or destroying some noxious products detrimental to plant growth. 



A 5-year field test with manganese sulphate was made, growing 

 wheat, rye, corn, cowpeas, and potatoes. The experiments were 

 made on a silty clay loam soil which is acid in nature. 



The manganese sulphate used at the rate of 50 pounds per acre had 

 a harmful effect on each of the crops grown. 



The addition of manganese sulphate to the soil decreased rather 

 than increased the oxidizing power of the soil, which at best does not 

 possess strong oxidizing power. 



This is in harmony with the crop yield, which was also lessened 

 by the addition of manganese sulphate, for while crop production is 

 not absolutely correlated with the oxidative power of a soil, yet, in 

 general, soils of good productivity are good oxidizers, and the factors 

 which favor oxidation favor soil productivity. 



The catalytic power of the plots was slightly if at all increased by 

 the addition of manganese sulphate. 



The soil is acid in character, which condition is unfavorable to 

 oxidation and catalysis. 



The failure of manganese to* increase these factors may therefore 

 be due to the acid character of the soil. 



From these tests it is concluded that manganese is not profitable as 

 a soil treatment on soil of this nature in need of liming. 



ADDITIONAL COPIES 



OF THIS PUBLICATION MAY BE PROCURED FROM 



THE SUPERINTENDENT OF DOCUMENTS 



GOVERNMENT PRINTING OFFICE 



WASHINGTON, D. C. 



AT 



6 CENTS PER COPY 



WASHINGTON : GOVERNMENT PRINTING OFFICE : 1BH 



