40 The Colorado Experiment Station 
We have given samples taken from alkalized land showing re¬ 
spectively o, 40, 80, 20 and 25 p. p. m. nitric nitrogen associated 
with 7,693.4; 18,554.0; 19,024.0; 18,743.0 and even 261,000.0 p. 
p. m. of chlorin. We also selected surface samples from brown 
spots which showed but slight or no incrustations of white lakali. 
Very pronounced brown spots gave 8,970.9; 1,229.7; 15,275.0 and 
5,231.5 p. p. m. nitric nitrogen. The chlorin in these cases was 
high, but without any definite relation to the amount of nitric 
nitrogen. We have for instance in the white alkali 20 p. p. m. nitric 
nitrogen with 19,024 p. p. m. of chlorin. In a very extreme brown 
spot we have 15,275.0 p. p. m. nitric nitrogen and 18,908 p. p. m. 
chlorin. We have before now tested such spots and found no living 
bacteria in the surface, but they were alive a few inches below it 
and at the edges. 
The surface soils of sections 4 and 5 gave respectively 117.0 
and 24.0 p. p. m. nitric nitrogen. A brown spot lying just between 
these sections gave 7,076.0 p. p. m., while a sample taken just out¬ 
side of the brown spot showed only 16.0 p. p. m. of nitric nitrogen. 
At another time the inner portion of this spot gave 10,000.5 p. p. m. 
nitric nitrogen This ground is about equidistant from holes No. 1 
and 2, probably a little nearer to hole No. 2. These facts are general. 
I have elsewhere stated that the Azotobacter pigments are not the 
cause of all brown spots any more than nitre is the cause of the death 
of all trees. I recall stating that one dark colored piece of land 
owed its color to the presence of calcic chlorid and others to the 
presence of salt, and others simply to organic matter. But usually 
we can recognize the brown spots due to the Azotobacter pigments. 
I selected another place to make observations similar to those just 
recorded, but we were so unfortunate in taking our samples, mostly 
due to the weather, that I have given the samples taken the weight 
of miscellaneous samples, though they are really members of a sadly 
broken series. The nitrates developed for the first time in this 
section of the country about 1909. Previous to that if present, as 
I suppose they really were, their development was not prominent 
enough to attract attention. There is an abundance of alkali all 
over this mesa, which was apparent the first time that I saw the 
section. Samples of soil rich in alkali gave 14 p. p. m. nitric nitro¬ 
gen, ordinary white alkali soil, surface, 40 p. p. m. nitric nitrogen, 
and 235,584 p. p. m. chlorin, while a very brown spot showed 
5,498.0 p. p. m. nitric nitrogen with 17,016.0 p. p. m. chlorin. This 
spot was exceedingly sharply defined. A sample taken almost at 
the edge of this carried 12 p. p. m. Some spots at this place that 
were very bad in 1911 had entirely disappeared in 1912. These 
spots do not by any means always occur in unfavorably located land. 
