i8 
Colorado Experiment Station. 
hill was the difference in the physical condition brought about by culti¬ 
vation to conserve the moisture. Two samples were taken, Oct. 26, 
1910, from this orchard, one (No. 17) from between the rows of trees 
well out in the tract, and the other (No. 18) from a ditch bank where 
the moisture conditions should have been more favorable for the 
growth of the soil bacteria. In culture, neither of these soils produced 
any surface film and gave only a thin, white membrane in the bottom 
of the flask. The nitrogen determinations after thirty days indicated 
that the soil from the ditch bank had actually lost nitrogen while the 
increase with the other was so slight as to be negligible, (.35025 m. g.) 
If any conclusion can be drawn from the examination of samples Nos. 
16, 17, 18 it would seem to indicate that our adobe shale soils both in 
the raw state and during early cultivation lack nitrogen fixing powers. 
Sample No. 19. 
The next sample was taken July, 1910, in a bearing orchard where 
the burning had appeared for the first time the previous year. There 
was no well defined area in which one could say that the trouble was 
worst but it was scattered throughout. In all, about two and one-half 
acres had been killed when I visited the ranch. The soil is a sandy 
loam which cultivates beautifully. It is underlaid with gravel at five 
and a quarter feet in whch there is a little water at Ernes. A hole six 
feet deep was dug in this orchard and allowed to remain open for one 
year for the purpose of seeing if there was an excess of water in this 
soil which could be removed by proper drainage. At the end of the 
time stated, the hole was as dry as the day it was put clown. The brown 
color was plainly visible on the sides and crests of the irrigation fur¬ 
rows and the trees were dying in a manner that we have come to rec¬ 
ognize as specific for nitre burning. The sample from this orchard 
was taken from between the irrigating furrows near a tree that was 
just beginning to burn. In culture, there developed a heavy gelatin¬ 
ous, white, wrinkled membrane with scattered brown patches. Abund¬ 
ant Azotobacter cells were present. After thirty days, it showed- an in¬ 
crease of 9.807 m. g. of nitrogen. 
Sample No. 20. 
Although I felt reasonably certain at the outset that we would se¬ 
cure little, if any, fixation with this soil, I was interested in learning 
whether, when an orchard died in a phenonemally short time, as was 
true here, the Azotobacter were likewise killed. There were about 
thirty acres altogether in the orchard, fifteen of which died between 
June, 1909, and July, 1910. Sample No. 20 was taken from that sec¬ 
tion which had been destroyed in 1909 and which had received no 
water during 1910 so that by July the surface was very hard and dry. 
The soil varied from a sandy loam to a clay loam with no water 
at six feet. In culture, a delicate, white, membranous film was formed 
on the surface with some flocculent growth in the liquid. A sour, earthy 
odor was developed. The increase in nitrogen amounted to only 2.5218 
m. g. in thirty days, demonstrating again that the concentration of the 
