814 EXPERIMENT STATION RECORD. 



growth is an indication of tlie probable presence of alkaline carbonates in the 

 soils. A marked development of Azotobacter in a mannite solution containing 

 no phosphoric acid is taken to indicate that the soil tised is probably not 

 deficient in phosphoric acid. 



It was found further that soils producing no fermentation of mannite in a 

 lime-free mannite solution were very deficient in lime. This is taken to indi- 

 cate that the degree of fermentation produced under such conditions serves as a 

 measure of the amount of lime present in a form available to mannite-ferment- 

 ing bacteria. 



The addition of phosphoric acid to a peptone solution inoculated with decom- 

 posed peptone markedly aided the decomposition of the solution. The addition 

 of carbon compounds did not accelerate decomposition, but humus and ferric phos- 

 phate did. Studies of the decomposition of peptone by soils, using inoculated and 

 uninoculated cultures, showed that lowland moor peat soil possessed a much 

 greater power for decomposing peptone than upland moor peat soil. The upland 

 moor peat contained substances which inhibited peptone decomposition, but 

 which were rendered inactive by adding calcium carbonate. Additions of cal- 

 cium carbonate and phosphoric acid and of phosphoric acid alone to acid low- 

 land moor peat favored peptone decomposition. Inoculation of the lowland 

 moor peat cultures had no effect, l>ut inoculation of the upland moor peat cul- 

 tures markedly favored the decomposition of peptone. 



In cultivated mineral soils peptone decomposition varied greatly. The 

 phosphoric acid content of the .soils especially influenced the degree of de- 

 composition. All the soils tested appeared to contain suflicient humus for 

 maximum peptone decomposition. With reference to the effect of inoculation 

 of cultures with decomposed peptone the mineral soils were of two groups, 

 namely, (1) those in which inoculation had little or no effect on peptone decom- 

 position and which were in all cases basic, and (2) those in which inoculation 

 markedly favored peptone decomposition and which were not basic. It is 

 concluded that a soil of low peptone decomposing power forms an unfavorable 

 medium for crop gro^vth. 



The decomposition of cellulose was usually found to be very small in humus 

 soils. With upland and lowland moor soils practically the same differences were 

 observed in cellulose decomposition as in peptone decomposition, except that the 

 influence of chemical factors was more marked. Next to the content of basic 

 lime and phosphoric acid, the availability of the organic nitrogen in peat was 

 the factor controlling the decomposition of cellulose. In mineral soils it was 

 found in all cases that the chemical condition of the soil mainly conti'olled cel- 

 lulose decomposition, basic lime and phosphoric acid being the controlling 

 factors. 



In both humus and mineral soils nitrification was found to be governed 

 mainly by their biological condition. 



A list of references to literature bearing on the subject is appended. 



On the presence of Azotobacter in Danish, •woods and on the value of 

 Azotobacter cultures for the determination of the lime requirements in 

 -woodland, F. Weis and C H. IJornebusch {Forstl. Forsopsr. Dfinmark, J^ 

 {1914), No. 4, pp. 319-337; abs. in Intcnwt. InM. Apr. [Rome], Mo. Bill. Agr. 

 Intel, and Plant Disca.'<es, 6 (1915), No. Jf, pp. 5.}6-.>-J8). — Experiments using 

 Beijerinck's nutritive medium to determine the Az(ttobacter content of soils 

 from 64 different localities in Danish forests are repi>rteil. 



Azotobacter was found in only two of the soils, both of which showed marked 

 alkalinity. In culture experiments in which the soil in question was substi- 

 tuted for calcium carbonate in Beijerinck's solution positive results were ob- 

 tained in 32 out of 54 cases. " In several cases the dry leaves fallen to the 



