1915] CURRENT LITERATURE 499 
HEADDEN’S studies of the chemical composition of “niter spots’’ 56,7. 8 
have shown that, in many cases, nitrates may be present in the first foot of 
the soil in amounts approximating 133 tons per acre-foot, while in many cases 
nitrate accumulation is progressing at rates varying between 2 and 22 tons 
annually per acre-foot. It is HEADDEN’s contention that the quantities of 
nitrates found bear no constant ratio to the amounts of chlorides or carbonates 
_ present or to the total water-soluble salt content, and that the high nitrate 
content is confined to the first few inches of the soil, and he regards these 
facts, together with the extent of the affected areas and their dissimilar geologi- 
cal relations, as strong evidence against the theory that the condition can be 
due to seepage from nitrate-bearing rocks with subsequent deposition from 
surface evaporation. 
SACKETT?: © has attacked the problem from the bacteriological side and 
rich igh in ape. ant eee of Cyanophyceae, which may be considered as 
supplying vailable as a source of energy for Azotobacter. SAcK- 
Ett farther concludes Ha his studies of the ammonifying and nitrifying effi- 
ciency of Colorado soils. that ammonification and nitrification proceed in 
them at rates considerably in excess of those found by workers in other parts 
of the United States. It must be said in criticism of SACKETT’s work that, 
while his own ammonification cultures were in all cases continued for a period 
of seven days, he has compared the amounts of ammonia produced therein 
5s HeappeN, Wm. P., The fixation of nitrogen in some Colorado soils; a further 
study. Bull gus Aonk Exper. Sta. no. 178. pp. 1-96. 1911. 
e fixation of nitrogen in Colorado soils; the distribution of the nitrates 
and aie elation to the alkalies. Bull. Colorado Agric. Exper. Sta. no. 186. pp. 
I-47. I 
7_—, The excessive quantities of nitrates in certain Colorado soils. Jour. 
Indust. and Kae. ichicy 6:586-590. 1914. 
; , Do Azotobacter nitrify? Science N.S. 40:379-381. 1914. 
9 SACKETT, WALTER G., Bacteriological studies of the agen of gaara in certain 
Colorado soils. Bull. Caceidc Agric. Cie Sta. no. 179. are I 
* 
———., Bak ogische Unt 
Bodenarten von Colorado. Centralbl. Bakt. wa 81-115. 1912 a transle- 
tion ot previously published paper just cited). 
* Ropprns, W. W., Algae in some Colorado soils. Bull. Colorado Agric. Exper. 
Sta. no. 184. pp. 24-36. 1912. 
” SacKETT, WALTER G., The ammonifying efficiency of certain Colorado soils. 
Bull. Colorado Agric. Exper. Sta. no. 184. pp. 1-2 
‘3. The nitrifying efficiency of certain Colorado soils. Bull. Colorado Agric. 
Exper. Sta. no. 193- pp. 1-43. 1914. 
