Fixation ot Nitrogen in Cotorado Soils 37 
i, 
is the soiiree of the nitrogen contained in them. The main pur- 
- ]>ose of tliis bulletin is to ascertain liow the nitrates in the well- 
waters are related to the nitrates in the surface soil; or, put 
’ otherwise, to ascertain whether the nitrates in the water have 
; been formed in the soil and have gone into solution in the water, 
I; or whether they were first present in the water and were sub- 
f seqiiently brought to the surface with it and left when the 
: water was evaporated. In other bulletins the question of the 
i. source of the nitrogen, now present as nitrates, has been con- 
I stantly held in view and repeatedly stated. 
Dr. Sackett used 38 different samples of soil, some taken 
from the surface of nitre-s])ot8, others taken at different depths 
i in the nitre-spots, others taken from the edges of these spots 
j and others taken from unaffected ground outside of these spots. 
‘ The results of his investigation show that often the surface por- 
tion of the nitre areas do not fix nitrogen, while at a depth of 
! G inches it still has some fixing power; but at the edges and 
i slightly beyond, the fixing power is much higher than usual. 
' Dr. SacketFs experiments were made by introducing soil ex- 
j tracts into a culture medium, and were strictlv controlled lab- 
oratory experiments. The results showed conclusively that 
these soils actually possess the power to take nitrogen from the 
air, whereas the samples of raw adobe soil tested did not pos- 
sess this power. 
I was not entirely satisfied with the general method of in- 
vestigation and made some experiments with soils that pre- 
sented the indications observed in these nitre-areas adding 
nothing. In one case I kept the moist soil as it was taken from 
the field at ordinary temperatures, and in other cases I added 
enough ammonia-free water to make the moisture content of the 
I soil from 15 to 18 percent., and keeping them at a temperature 
of 27° to 30°C. These experiments gave positive results — 
quite as pronounced as those obtained by Dr. Sackett in his 
cultural solutions. Dr. Sackett made a parallel experiment and 
1 he also obtained positive results. This procedure removed all 
questions of manipulation and artificial conditions except the 
' fact that these experiments were made in the laboratory. Some 
of my experiments were made in the light and some in darkness. 
This did not appear to make any difference. 
I FIXATION AND NITRIFICATION UNDER FIELD 
CONDITIONS 
In order to eliminate the questions attaching to the fact 
that all of these experiments were made in our laboratories and 
with comparatively small quantities of earth — 1200 grains in 
