4 
Colorado Experiment Station. 
itself. It sometimes occurred in light and sandy loams, and some¬ 
times in clayey soils. It is sometimes in comparatively , low lying 
lands, again in the low lying portions of higher lands, and again on 
the hillsides. The road side, a ditch bank, and the cultivated fields 
represent the range of places in which this thing may reveal itself. 
There is one thing common in all of its occurrences, namely, a brown 
color in the surface soil. This color is less marked in the sandy soils 
than in the so-called adobe soils. Perhaps this is due to the presence 
of the deliquescent salts on the surface of the adobe soils, or more 
probably to the color of azotobacter films.” 
Fig. 1. Nitre area in an orchard showing the characteristic dark spots. 
Sample No. 30. 
“We find the nitrates present in soils, where there is a great deal 
of moisture, but in places where there is too much water, the nitre 
does not appear. In little valleys and saucer shaped depressions in 
which the lower portions are too wet, there is no visible alkali, then 
follows a zone where white alkali abounds and above this the nitre is 
formed. I do not mean to say that there may not be nitre mixed with 
the white alkali, but that the nitre in such cases appears on higher 
ground than that on which the white alkali usually appears. Further¬ 
more, it is not intended that anyone shall infer that it is only in val¬ 
leys and depressions that the nitre occurs.” 
