MAXGAXESE UXDEE ACID AND NEITTEAL SOIL CONDITIONS. 5 



OXTOATIVE POWER OF PLATS WITH AND WITHOUT MANGANESE UNDER 



ACID CONDITIONS. 



Bertrand ^ showed that manganese played an essential part in the 

 oxidation by the so-called oxidizing enzym laccase. Fui-ther, since 

 manganese increased the oxidizing power of a number of soils tested 

 by the Office of Soil-Fertility Investigations and it has been found 

 that a number of soils of strong oxidizmg power contain considerable 

 manganese, some of which was in the highly oxidizing form of INinOg, 

 it became of interest to determine whether the manganese had any 

 accelerating effect on the oxidation in the soil of the field plats 

 planted with wheat, rye, corn, cowpeas, and potatoes. 



In 1912 composite samples from five borings to the depth of 6 

 inches were taken of the manganese plats and check plats (1) early 

 in April, (2) late ui May, and (3) m August. The oxidation readings 

 were made on the air-dried samples within two weeks after collection. 



When 10 or 20 grams of soil are shaken two or three times with 50 

 to 70 c. c. of a 0.125 per cent water solution of aloin, the aloin solu- 

 tion is changed ui a few minutes from a bright yellow to a cherry red. 

 After the soU has stood for about an hour and has settled, the some- 

 what turbid solution is decanted and centrifuged, the supernatant 

 Hquid dra\\ni off, and the depth of color of the different solutions com- 

 pared by means of a Schremer colorimeter, either with each other or 

 with colored glass of a shade of red matching the oxidized solutions. 

 In the present experiment the oxidation reading was made against a 

 glass standard which matched in tint the red color produced in the 

 alom solution by the sample of wheat soil collected in the spring. 

 Ten grams of sod were employed for each test. The relative oxida- 

 tion in the manganese plats and the check plats is given in Table III. 



Table III. — Relatire oxidation in plats treated with manganese sulphate and in the 

 conresponding check plats . growing the same crops {wheat soil in April being taken 

 as 1011). 



f'roj). 



Wheat.. 



Ryo. 



Corn 



Cowpea-j 

 Potatoes 



April. 



June. 



Aug 





Plats 





Plats 





Un- 



treated 



• Un- 



treated 



TTn- 



treated 



with 



treated 



with 



treated 



plats. 



man- 



plats. 



man- 



plats. 





ganese. 





ga ne.se. 





100 



95 



no 



i:w 



55 



131 



lO.') 



lil 



105 



7H 



no 



1()0 



KJO 



131 



87 



06 



(H 



lOfj 



no 



53 



S7 



m) 



91 



78 



53 



]'lats 

 treated 

 with 

 man- 

 ganese. 



' Bertrand, Gabriel. Sur les rapports qui oxislont entro la coastllutlon chimicjues dos composes organi- 

 (lues ct Icur o.xydabillti'- .sfjiis rinJIuence dc la laccase. In ('onii)l , Mond. Acad. Sci. [Paris], t. 122, no. 20, 

 p. 1132-11.31. l«9fl. 



Sur rinlervention du n'uiigun^jso dans les o.xydulions ]>rov()'|iii'.es par la laccase. In ( iiiiiiil. 

 Kend. Ac-a<l. .Sc-1. (J'arLs), t. Vi\, no, 10, p. I(W2-1(«5. 1X97. 



