968 Journal of Agricultural Research vol. vi.no. 24 



will not permit similar accumulations. The work of the Bureau of Soils 

 has also demonstrated that calcium carbonate is rather efficient in 

 eliminating the toxic effect of certain decomposition products found in 

 soils, and the beneficial effect might, in part, be due to an action of this 

 nature. 



The following data were obtained during 191 3 concerning the relative 

 effect of 6 years' application of manure compared with that for 25 years: 

 Plot 29, continuous wheat, received manure for 6 years and produced 

 in one week's incubation an average of 5.35 mgm. of nitrate; in four 

 weeks an average of 116.6 mgm. In the inoculation experiments it 

 produced 15.3 mgm. Plot 30 received manure for 25 years, otherwise 

 similar to No. 29, and produced in one week 6.5 mgm. of nitrate; in 

 four weeks 127 mgm., and in inoculating experiments, 27.5 mgm. This 

 indicates that the shorter period of application has produced almost the 

 same effect as the longer. 



NITRIFYING INOCULATION EXPERIMENTS 



The results of the nitrifying inoculation experiments are reported in 

 Table VIII. It should be borne in mind that the 191 3 results were 

 obtained under conditions not favorable for nitrate formation, no calcium 

 carbonate having been added. Therefore, too much weight should not 

 be attached to these results. The 1914 results, however, were secured 

 under favorable conditions. It is worthy of note, though, that there is 

 a very close agreement between the relative rank of the plots in the 

 inoculating experiments for both seasons and the nitrate-forming experi- 

 ments. This is shown in Table IX, together with the relative position 

 of bacterial numbers. 



The agreement is not absolute, but it is close enough to indicate the 

 probability of the same factors controlling the nitrate formation in the 

 two instances. This being true, the factors must be biological in nature 

 rather than chemical or physical; otherwise they probably would not be 

 transferred in 20 c. c. of a 2 to 1 soil suspension in sufficient quantities 

 to exercise much influence. There is also exhibited here a close correla- 

 tion between bacterial numbers and nitrate formation. Since, however, 

 no such correlation can be traced in ammonia formation, there is little 

 reason for believing the two factors connected other than that probably 

 the factors controlling both are the same. 



