PHOSPHORUS 203 



strong aeration decreased at least in many cases the quantity of 

 ammonia split off from peptone solutions which had been inoculated 

 with soil. Plimmer, working with a Dunkirk clay loam, failed to 

 find any optimum oxygen-,content for the maximum production of 

 ammonia. Under purely anaerobic conditions, caused by an 

 atmosphere of pure carbon dioxid, there was somewhat less ammonia 

 produced than when oxygen was present at the beginning, but even 

 under these conditions ammonia was formed in rather large pro- 

 portions. This would probably vary with the specific bacterial 

 flora of the soil, for the work of Marchal demonstrated that the 

 formation of ammonia is favored by the unhindered access of oxygen, 

 and in the process considerable quantities of oxygen are used up and 

 a nearly corresponding quantity of carbon dioxid produced. There 

 is the possibility of the carbon dioxid resulting from side reactions, 

 the oxidation of the carbon chain compounds which have been 

 deaminized, and not due to the main process of ammonification. 

 For theoretically, at least, ammonification can be considered as a 

 true hydrolytic reaction. The microorganism, however, gets its 

 energy from the oxidation of the carbon, and where conditions are 

 favorable ammonia production follows very closely the evolution 

 of carbon dioxid. But Gainey found unfavorable conditions to 

 have a more detrimental effect upon the f ormatiori of ammonia than 

 upon the production of carbon dioxid. 



Lime and Magnesia. These exert a marked effect on ammoni- 

 fication, and Vorhees, Lipman, and Brown found magnesium lime 

 usually superior to non-magnesium lime in this respect. Its effect 

 varied, depending upon the character of the organic matter to be 

 ammonified and the crop grown upon the soil. Lipman, Brown, 

 and Owen found lime carbonate in which the large per cent, of 

 boron proved to be the factor which hindered decay bacteria. 



The increased ammonia resulting from the use of the magnesium 

 lime may be due to an apparent and not to a real increase in ammoni- 

 fication. For Fischer has noted that calcium carbonate increased 

 the speed with which ammonia sulphate is transformed into protein 

 to a greater extent than did magnesium carbonate. Moreover, 

 Lipman and Green found that magnesium carbonate interferes with 

 the speed with which nitrite is converted into nitrate which would 

 slow down the action of the nitrosomonas. In either case this 

 would increase the accumulation of ammonia in the soil, which may 

 be interpreted as increased ammonification. 



Phosphorus. In experiments on ammonia cleavage by Dzierzbicki 

 in peptone solutions, it was found that the intensity of such cleavage 

 depends not only on the bacterial flora of the soil but more so on its 

 chemical composition and especially on the presence of phosphoric 

 acid. Monocalcium and dicalcium phosphate are equally effective, 



