CURRENT LITERATURE 
NOTES FOR STUDENTS 
Niter spots.—The occupation and cultivation of vast areas of semi-arid 
lands in Utah, Wyoming, and Colorado, which has been made possible by the 
development and extension of irrigation systems, has brought agricultural 
workers in these states face to face with many new problems. Possibly none 
of these has been more striking than that presented by the sudden appearance 
in the soil of nitrate accumulations in amounts sufficient to produce complete 
sterility over considerable areas which had previously been normally pro- 
ductive. Since the areas thus affected are widely scattered and embrace some 
of the most valuable agricultural lands of these states, the search for the causes 
of the condition has occupied the attention of a number of workers, and a very 
considerable literature, some of which borders upon the controversial in char- 
acter, has resulted. 
HEADDEN, who has been longest engaged in studies of the problem, was 
first to call attention to the extent and gravity of the condition, and to point 
out that most cases of sudden destruction of orchards, while popularly attrib- 
uted to “black alkali” (sodium carbonate) from irrigation waters, were in 
reality due to nitrate accumulation. Contrary to H1tcarp,‘ who attributed 
an increase in nitrates observed in certain irrigated soils of southern California 
to rapid transformation of organic matter previously accumulated in the soil, 
HEADDEN?:3 has advanced the theory that fixation of atmospheric nitrogen 
by Azotobacter, with concurrent bacterial transformation of the resulting nitroge- 
nous compounds into nitrates, is responsible for these accumulations. This 
author has shown that orchard trees, alfalfa, or other crops in the affected areas 
uniformly show characteristic injury quite unlike that produced by excessive 
irrigation or by sodium carbonate or other alkali salts, but identical with that 
produced by excessive use of nitrate fertilizers. He also attributes the rather 
widespread deterioration in yield, sugar content, and keeping qualities of sugar 
beets to accumulation of nitrates in the soil. 
satis, E. W., Soils. New York: Macmillan. rgr11. pp. 68, 69. 
*HEADDEN, Ws. P., The fixation of nitrogen in some Colorado soils. Bull. 
Colorado Agric. Exper. Sta. no. 155. pp. 10-69. IQIO 
, Nitrates in the soil; an explanation of coil “black alkali” or 
ek ae ” Bull. Colorado Agric. Exper. Sta. no. 160. pp. 1-8. 1910. 
‘ HEADDEN, Ws. P., Deterioration in the quality of sugar beets due to narrates 
formed in the soil. Bull. Colorado Agric. Exper. Sta. no. 183. pp. 1-184. 1912. 
408 
