SOILS — FERTILIZERS. 317 



was taken to itrcveiit inoculation except from other soils. The number of bac- 

 teria in tlie sterilized soil increased to an enormous number in tlie course of 

 several uiontbs, but as tiiere was practically no increase in nitrates it is evident 

 that either nitrifying bacteria did not enter the soil or that their growth was 

 inhibited." 



Among tlie more important new facts brought to light by these experiments 

 are the following: 



*■ Steaming the soil at 2 atmospheres pressure for 2 hours or 4 hours reduces 

 the nitrates of the soil to nitrites and to ammonia, but most of the ammonia 

 is formed from organic nitrogen. 



" On standing for various periods up to 3 months, without plants growing 

 on them, the steamed soils steadily decreased in their content of soluble matter, 

 including ammonia and nitrogenous organic matter. 



"Ammonification as well as nitrification (the latter mentioned by Deherain 

 and De Moussy) were practically nonexistent during the 3 months following 

 steaming. 



"The time required for the soils to recover from the injurious effects of 

 steaming, as shown by the better growtli on the steamed than on the un- 

 steamed soils, was with one exception in the order of their relative produc- 

 tiveness. 



" Wheat seedlings grown in the aqueous extract of the freshly steamed soil 

 grow less well tliau those in the extract of the nnsteamed soil, but when the 

 extracts were diluted the better growth was made by the seedlings in the 

 extract of the steamed soil. The results indicate the production of injurious 

 substances during the steaming process. 



" Steamed soil on which wheat was grown for 3 months contained decidedly 

 more soluble matter at the end of that time than did that jiortion of the soil on 

 which no plants were grown, but whicli stood for the same length of time under 

 similar conditions. 



'• The growth of wheat plants on the steamed soil served to hasten its 

 recovery from the injurious effects of steaming. 



" The effect of adding an infusion of unsterilized soil to the same soil steamed 

 was to increase greatly the germination of seeds and the early growth of the 

 plants, but to retard later growth, so that the second crop was very much 

 smaller on the steamed soil to which the infusion had been added than on the 

 steamed soil not so treated. 



"Another effect of the infusion was to hasten the disappearance of total 

 water-soluble matter, but it did not increase nitrification nor did it apparently 

 increase anunonification, at least when plants were not growing on the soil." 



On the biochemical cycle of phosphoric acid in cultivated soils, R. Perotti 

 (8ul Ciclo liiorliimico dclV Anidride Fosforica nel Terrcno Agrario. Rome, 

 J909, pp. VII +231, pis. 2, figs. 15; Staz. Sper. Agr. Ital., J,2 (1909), No. 8, pp. 

 531-552; Crnthl. Bald, [cic.^, 2. Aht., 25 (1909), No. L'l-JS, pp. .',09-.'i 19). —The 

 author claims to have established the following facts: 



In soils in which micro-organic processes are at worlv many bacteria exist 

 which are able, under favorable conditions, to decompose phosphoric acid. The 

 presence of carbohydrates in the culture media had a marked influence on 

 bacterial solution phenomena, especially when a 2 per cent solution of cane 

 sugar was used. The sources of the nitrogen in the liacterial cultures had a 

 great influence on the ability of the bacteria to decompose the phosphoric acid; 

 the ammonium salts in general, which are physiologically acid, favored them to 

 a noteworthy degree, both as to intensity and duration of the action. This was 

 especially true of the sulphate and chlorid of ammonium. The influence of the 

 bases varied with the nature of the elements and the form of combination, but 



