SOILS FERTILIZEES. 121 



Determinations of tlie numbers of liacteria in soil under different conditions 

 indicated not only an enormous increase in tlie presence of peptone but also an 

 approximate relation between the number of bacteria and the amount of am- 

 monia produced. 



In experiments on red shale and clay loam soils with peptone, urea, dried 

 blood, and albumen, it was found that ammonification was most active in the 

 clay loam soil in case of the peptone and in the shale soil with urea and dried 

 blood. As measured by ammonification the urea, peptone, dried blood, and egg 

 albumen were available in the order given. 



Minor studies on nitrification, denitrification, and nitrogen fixation in the 

 same soils, and on media for quantitative estimation of soil bacteria, as well 

 as miscellaneous data concerning the growth of Azotobacter in culture solu- 

 tions are also reported. The latter studies included the influence of small 

 amounts of calcium carbonate, acid potassium phosphate, previous treatment 

 of the soil, and varying amounts of mannite on 'the nitrogen fixation of Azoto- 

 bacter. 



Soil inoculations with A. hcyerincki in soils on which corn was grown gave 

 results which are summarized as follows : " Ground limestone hastened the de- 

 composition of the inert humus compounds and made available a larger supply 

 of nitrogen to the corn crop. Applications of ground limestone at the rate of 4 

 tons per acre proved even more effective than applications of 2 tons per acre in 

 hastening the decomposition of the inert humus compounds. Applications of 

 sugar, starch, and ground filter paper depressed the yields of dry matter and 

 of nitrogen in the corn crop. Inoculation with A. bcycrinchi in the presence or 

 absence of organic substances depressed rather than increased the yields of dry 

 matter and of nitrogen in the corn crop." 



The effect of partial sterilization of soil on the production of plant food, 

 E. J. Russell and H. B. Hutchinson (Contrib. Lab. Rothamsted Expt. Sta., 

 1909, pj). lll-lJf.'f, pis. 2, figs. -}; ret>rinted from Jour. Agr. Sci., 3 {.1909), Wo. 2, 

 pp. 111-l^Jf, pis. 2, figs. Jf). — The soil used in these investigations contained mod- 

 erate amounts of nitrogen, organic matter, and calcium carbonate. It was par- 

 tially sterilized, either by heating to 98° C. or by adding 4 per cent toluene. In 

 the latter case the toluene was either allowed to evaporate at the end of 3 days 

 by spreading out the soil in a thin layer or it was left in the soil during the 

 whole of the experimental period. In a few of the experiments the soils were 

 heated to 125° to kill all organisms. After treatment the soils were moistened 

 and kept for definite periods at ordinary laboratory temperatures in bottles 

 stopped with cotton wool. 



Observations were made on the production of ammonia and unstable nitrogen 

 compounds, changes in humus and total amount of nitrogen, and on nitrification, 

 and the part played by bacteria in these transformations. The effect of the 

 treatment on the productiveness of the soil was studied in pot experiments 

 with rye. 



The results showed that partial sterilization increased the amount of am- 

 monia produced and the increased productiveness of soils so treated is ascribed 

 to this increase of ammonia, 



" The excess of ammonia is the result of increased decomposition of soil sub- 

 stances by bacteria. 



" Hiltner and Stiirmer's discovery that the bacteria increase rapidly after 

 partial sterilization, and finally become much more numerous than in the origi- 

 nal, untreated soil, is confirmed. The increase in number proceeds pari passu 

 with the increase in ammonia. 



" The new bacterial flora arising after partial sterilization is a more potent 

 decomposing agent than the original flora, but tbe individual species have not 



