the: nitrifying efficiency of certain COLORADO SOILS 
23 
clay; moist; no white alkali; general mountainous vegetation ; nitric 
nitrogen 2 p. p. m.; chlorin 8 p. p. m. 
Sample No. 70. —California. Received April 2, 1913; “black 
adobe"; no white alkali; moist; small grain in 1912, nitric nitrogen 
5 p. p. m.; chlorin 10 p. p. m. 
Sample No. 71 .—California. Received March 7, 1913; sand 
and gravel from raw cactus land; moist; no white alkali and no brown 
color; nitric nitrogen, none; chlorin 6 p. p. m. 
Sample No. 73. —California. Received April 2, 1913; sandy loam; 
no white alkali; no brown color; moist; formerly a vineyard; small 
grain in 1912; nitric nitrogen 7.4 p. p. m.; chlorin 8 p. p. m. 
Sample No. 74.—Garden City, Kansas. Received April 17, 1913; 
sandy loam; sugar-beets for past two years, 1911 and 1912; nitric 
nitrogen 26 p. p. m.; chlorin 2,000 p. p. m. 
DISCUSSION OF RESULTS. 
Colorado Soils. 
Series I. Ammonium Sulphate 
In Table No. 1, will be found the results of our nitrification ex¬ 
periments with Colorado soils and ammonium sulphate. Of the twen¬ 
ty-three soils under study, 17 showed a very marked net gain in 
nitric nitrogen over the checks; one gave the same increase as the 
corresponding soil which received no ammonium sulphate and there¬ 
fore is considered as having given no net gain(i) ; five contained less 
than in the beginning. The point of greatest interest in this series is 
the uniformly large gains which all of the positive soils made. There 
are no small increases of 10, 20, or 30 parts per million as might 
be expected, the smallest being 320. Furthermore, there is some 
justification for setting aside this figure as the lowest since the sam¬ 
ple consisted of the surface crust from a brown area and does not 
represent a four to six inch section of soil as the others do. The nitric 
nitrogen was high to begin with, 600 p. p. m., and that may have had 
some retarding influence on the rate of nitrification. If No. 95 is 
eliminated, then we have the lowest net gain produced by any positive 
soil as 408 p. p. m. by No. 94, while the average is 672 and the maxi¬ 
mum 972. 
As a matter of interest in connection with Nos. 94 and 95, the read¬ 
er’s attention is called to the initial nitrate nitrogen in the two samples. 
It will be remembered that both were taken side by side, but that the 
former represents a soil-section a short distance from any brown ma¬ 
terial while the latter is just the brown surface; the first carried 34 p. 
p. m. and the second 600. The chlorin is considerably lower in the 
crust than in the section so it is probably the high nitrates that are re¬ 
sponsible for the relatively small increase in nitric nitrogen. 
(1) By the expression “total gain” is meant the increase in nitric nitrogen over the 
check at the beginning ; by “net gain” is meant the increase over the check at the end. 
