1915] CURRENT LITERATURE 501 
extending over a period of eight years, these workers never found a nitric 
nitrogen content exceeding 300 pounds per acre for a total depth of ten feet. 
STEWART has also studied the rate at which nitrification occurs in this soil, 
with results which indicate that the conditions rarely if ever permit this 
process to become eta a conclusion in entire accord with the results of 
McBeta and Sir. 
The extensive and oe controlled work carried on by these investigators 
for the past four years at the Greenville Experiment farm has shown that 
nitrification is practically confined in all cases to the first foot of the soil; that 
the application of irrigation water invariably diminishes the nitrifying power of 
the soil; that the water-content of non-irrigated soil, in a region having a well- 
distributed annual rainfall of 15.81 inches, is entirely too low throughout the 
summer months to permit of active nitrification; and that the nitrification 
period, would apparently entitle the results of these authors to acceptance as 
conclusive. 
STEWART and his associates have advanced the theory that abnormal 
accumulations of nitrates, wherever these may occur in the area which was 
submerged during later Cretaceous time, are due to transportation and depo- 
sition of leachings from the country rock, adducing proof that throughout 
Utah, Idaho, and Colorado, it is quite generally the case that the chlorine 
content of ‘‘niter spots” increases proportionately with the increase in nitrates, 
which they regard as conclusive evidence of a common origin of these elements. 
By recalculation of data presented by HEADDEN, these authors have shown 
that fairly definite ratios of increase between chlorine and nitrate hold for the 
Colorado nitrate areas, in one of which the supposed “fixation” of 621 pounds 
of nitrogen was accompanied by an increase of 236,883 pounds in the chlorine 
content of the first acre-foot! That any material activity on the part of nitri- 
fying bacteria can occur in the presence of the amounts of chlorine shown by 
Srewart and Greaves to be present in the soils studied by HEADDEN would 
seem impossible to the reviewer in view of the results of LipMAN. a 
Azotobacter can be responsible for an increase in soil nitrates which has been 
shown to occur at rates frequently exceeding 5000 pounds per acre-foot annually 
would seem equally impossible, since there would be required to supply the 
* A Beehast Rosert, The intensity of nitrification in arid soils. 
Bakt. 367:477-489. 1913 
McBeth, I. G., and Smirn, N. R., The influence of irrigation and crop pro- 
duction on soil OEP a Centralbl. Bakt. 407: et 1914. 
He gO esi ee y Wl, So, PUPR pS n coil hactenia Il. Nitri- 
» Lipman, C. B.,. Toxi 
fication. SOPOT ‘Bakt. i. 305-326. 1912. 
Centralbl. 
