128 University of California Publications in Agricultural Sciences [Vol. 1 



soil with its natural flora was employed. Tlie ammonia deter- 

 minations were made in accordance with methods described in 

 the papers above cited and the nitrate determinations in accord- 

 ance with the method described by Burgess." 



The work carried out by other investigators dealing with the 

 subject in hand has thus far been rather meager and but few 

 of the results possess pertinence with respect to our findings. In 

 studying the amounts of copper in vineyard soils due to accumu- 

 lation from copper-containing sprays. Prandi* was unable to 

 note any damage to vines after the copper sprays had been used 

 for a number of years. jMoreover. he did not adjudge dangerous 

 the amounts of copper which had accumulated in the soils 

 studied in the quantities in which he found it there. He does, 

 however, inake the further interesting speculative statement that 

 copper may have an important influence on the soil organisms. 

 The original work of Eickmeyer^ is unfortunately not accessible 

 to us and. while it may contain some of the most cogent infor- 

 mation on our subject which is in print, we can ascertain only 

 that the investigator named studied the effects of copper and iron 

 sulfates, among other poisons, on soil bacteria. In studying the 

 bacteriology of ammonium compounds Ehrenberg'' observes that 

 the cause of the difference in the effects of ammonium compounds 

 used for fertilizers in zinc pots and in the field must be that the 

 zinc exercises a deleterious effect on "ammonia-fixing" bacteria 

 which compete with the plants for soluble nitrogen in the soil. 

 Owing to that, he believes ammonium fertilizers stimulate plants 

 in zinc pots but have no effect in the field. Among studies on 

 the effects of the poisonous metals here considered, on some of the 

 lower organisms, may he mentioned those of Latham.' who 

 obtained stimulation with low concentrations of ZnSO^ for 

 Aspergillus nigcr, and those of Remy and Rosing.^ which indicate 

 a marked stimulating effect of iron on Azotobacter organisms. 



3 Uiiiv. Calif. Publ. Ajir. Sci., vol. 1, no. 4, p. 51. 



4Staz. Sper. Gr. Ital., vol. 40, p. o31, cited from E. S. R., vol. 19. p. 755. 



5 Winner Landw. Ztg., vol. 57, p. 600, cited from E. S. R.. vol. 19, p. 625. 



GFubling's Landw. Ztg., vol. 27, p. 449. 



' Cited from E. S. R., vol. 21, p. 421. 



s Cent. fiir. Bakt., 2'^ Abt., vol. 30, p. 349. 



