12 BULLETIN 441, U. S. DEPARTMENT OE AGRICULTURE. 
The action of manganese was studied on the same plats, kept 
neutralized with lime for the three succeeding years following the 
experiment with the soil in an acid condition. 
The productivity of the soil was increased by manganese under 
this neutral or slightly alkaline condition. With wheat, rye, timothy, 
beans, corn, and cowpeas the yields were increased, while with 
potatoes the yield was practically the same in the treated and the 
check plats. 
The oxidative power of the neutralized soil was also increased by 
manganese, which is in accord with the results of former investiga- 
tions, which have shown that the oxidation by manganese salts is 
greater under slightly alkaline conditions. 
The action of manganese in decreasing the oxidation in the soil 
while acid is in harmony with the decreased yield, and its action in 
increasing the oxidation of the neutralized soil is in harmony with 
the increased yield. The action of manganese in the acid soil was 
probably to stimulate the life processes in the soil, acting on the 
organic matter in such a way as to produce changes which resulted 
in a lessened crop-producing power, while its action in the neutralized 
soil was such as to stimulate oxidation and other biological processes, 
acting on the organic soil constituents and producing changes 
favorable to the growing plants. 
These results on the behavior of manganese as a so-called catalytic 
fertilizer when acting under acid or neutral soil conditions show that 
no profitable return is to be expected in soils of a persistent acid 
tendency until such soils are limed. 
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