6 BULLETIN 441, U. ffiii'HBRABTMipNT OF AGEICULTUEE. 



With the exception of the wheat plat, where there is shown a sHght 

 increase as an average of the three determinations, the addition of 

 manganese sulphate has not increased the oxidative power of the soil, 

 and in a number of instances it has lessened oxidation. The soil in 

 general has a tendency to be acid in character and at best has not a 

 strong oxidizing power. If the first determination, made in April, 

 is considered (that is, the oxidative power of the plats at a time when 

 there is little or no growth) the oxidation in the manganese plat is 

 less in every instance than that of the check plat. This period is the 

 best one for testing the oxidation effect of manganese unmodified by 

 plant growth. The lessened oxidation produced by manganese sul- 

 phate is in harmony with the lessened yields on the same plats under 

 treatment with manganese. In 1912, for instance, the year in which 

 the oxidation was tested, the yield, as previously shown, of wheat, 

 corn, and potatoes was less on the manganese plat than on the 

 untreated plat, while rye only showed a slight increase and the yield 

 of cowpeas was practically the same, 



In the second determination, made m June, the oxidative power of 

 the manganese plat is on the average more like that of the check plat. 



In the third determination, made in August, shortly after the wheat 

 and rye had been taken off, the manganese plat was on the average 

 again less than the check plat. 



As previously pointed out, the manganese plats, with the exception 

 of the potato and the wheat plats, showed a higher Hme requirement 

 than the check plats. Under acid conditions the formation of organic 

 compounds capable of acting as oxygen carriers or as activators of 

 inorganic oxidizing compounds, such as manganese salts, is much 

 lessened or entirely inhibited. This is also indicated from the results 

 with the acid soil under investigation, for the addition of manganese 

 did not increase the oxidizing power of the soil nor, indeed, of plants 

 growing therein. This oxidizing power of the plants was tested in 

 the case of wheat. By carefully removing the soil from the young 

 wheat plants growmg on the plats, the oxidizing power of the intact 

 rocits when placed in an aloin solution was found to be no greater in 

 the case of the plants from the manganese plat than from the check 

 plat. The relative oxidation was 97 and 100, respectively. 



EFFECT OF MANGANESE ON ARLINGTON SOIL UNDER NEUTRAL 



CONDITIONS. 



As the manganese had no beneficial effect on the soil under acid con- 

 ditions, the experiment was continued and the soil neutralized as 

 nearly as possible by applying lime from year to year. Three years' 

 results have now been secured. Each year before planting, the lime 

 requirement of the plats was determined by the Veitch method and 

 an excess of lime added to both the check and manganese plats. The 



