iyi4] Lipman-Burgess : Ammonification in Soils by Pure Cultures 171 



Summary 



Results are above given which deal with : 



1. The marked differences in ammonifying efficiency of fifteen 

 organisms in pure culture. 



2. The soil was used as a medium and three types employed, 

 sand}^, clay loam and clay adobe. 



3. Four common fertilizers as sources of nitrogen were used, 

 in all soils, and peptone, bat guano, and sheep and goat manure 

 employed only in the sandy soil, besides. The four fertilizers 

 were dried blood, tankage, cottonseed meal and fish guano. 



4. The nature of the soil, as well as the nature of the nitro- 

 genous material, markedly modify an organism's ammonifying 

 power. 



5. There is no regularity in these variations and they cannot 

 be foretold. 



6. While it is difficult to make an exact decision, B. fiimescens 

 appears, on the whole, to have been the most efficient organism 

 above tested. 



7. The highest efficiency in a single culture with a fertilizer 

 was shown by B. mycoides, which transformed in twelve days at 

 27° to 30° C, 36.06 per cent of the nitrogen in bat guano into 

 ammonia. 



8. The highest efficiency in a single culture with peptone was 

 shown by Sarcina lutea, which transformed 41.98 per cent of the 

 nitrogen present into ammonia under similar conditions. 



9. A comparison of availability of nitrogenous fertilizers with 

 ammonifiability as a criterion, according to our experiments, 

 markedly changes the positions of tankage, fish guano, and 

 cottonseed meal with respect to dried blood, showing them in 

 most or in many cases to be superior to the latter. 



10. One half of the number of organisms tested is far superior 

 to the other half in ammonifying ability. 



11. Interesting comparisons with ^Marchal's work are made. 



12. B. icteroides has shown itself throughout to possess but 

 little ammonifying efficiency. 



