30 



BULLETIN 42, TJ. S. DEPARTMENT OF AGRICULTURE. 



increased oxidation. Addition of manure increased the oxidation 

 power in general, but the effect of manure was not tested in con- 

 junction with manganese. 



CATALYTIC POWER OF PLOTS WITH AND WITHOUT MANGANESE. 



In previous work 1 it has been shown that in soil, as in plant and 

 animal tissue, there is associated with oxidation the power to decom- 

 pose hydrogen peroxide. The property of tissue to decompose hydrogen 

 peroxide has been attributed to an enzyme, cataluse, and the process is 

 known as catalysis. This process is greater in strong vital soils and 

 appears to be dependent not on an enzyme, but on the nature of the 

 soil constituents, especially manganese and the organic matter. 



In testing the catalytic power of soils, 5 grams of air-dried soil 

 were placed in a large test tube having a capacity of 90 c. c, pro- 

 vided with a two-holed rubber stopper through which passed a small 

 dropping funnel and a glass tube connected with a gas-measuring tube. 

 The peroxide used was a slightly acid and rather stable solution con- 

 taining approximately 3 per cent hydrogen peroxide by weight. 

 Before using, the peroxide was made faintly alkaline to phenolphtha- 

 lein by means of dilute sodium hydroxide and made up to 1.5 per cent 

 solution. The neutralized peroxide was dropped upon the soil by 

 means of the funnel, and the oxygen evolved was collected in the gas- 

 measuring tube. The criterion for the catalytic power of soils is the 

 rate of evolution of oxygen or the time required to evolve a definite 

 quantity, usually 50 c. c, but in soils of slight catalytic power 20, 30, 

 40 c. c, as the case may be. In this way many soils, productive and 

 unproductive, surface soils and subsoils, greenhouse soils and field 

 soils have been tested. The catalytic power is greater in strong vital 

 soils than in weak soils, in surface soils than in subsoils, and persists for 

 years in air-dried soils. It is weak in acid soils. 



Using the method just described, the catalytic power of the soils 

 of the plots was taken at the same time as the oxidative power — 

 (a) in April, (6) in June, (c) in August. On account of the relatively 

 slow catalysis, 30 c. c. was selected as the measure for comparison. 

 The results are given in Table XVIII. 



Table XVIIT. — Catalytic power of plots treated with manganese and of the corresponding 



check plots. 





Time required to evolve 30 c. c. of oxygen. 



Crop. 



April. 



June. 



August. 





Check 

 plots. 



Manganese 

 plots. 



Check 

 plots. 



Manganese 

 plots. 



Check 

 plots. 



Manganese 

 plots. 



Wheat 



Minutes. 

 36 

 13 

 11 

 28 

 24 



Minutes. 

 16 

 10 

 10 

 33 

 29 



Minutes. 



14 



9 



5 



26 



16 



Minutes. 



13 



9 



7 



23 



20 



Minutes. 

 15 

 13 

 6 

 19 

 16 



Minutes. 

 11 



Rye 



9 





8 





23 





20 







i Bui. 86, Bureau of Soils, U. S. Dept. Agr. 



