54 
Colorado Experiment Station 
One of the most difficult questions for us to answer is, Are there 
enough of these little plants and can they grow fast enough to build 
up all of the nitrogenous matter that is necessary to account for the 
nitrates that we find? A great many people think that we give them 
too big a job to do. I do not think that this is true. We have tried to 
find out not exactly what they may be able to do under very favorable 
conditions* but what they actually do in our ordinary cultivated soil, 
soil that we have growing wheat on and which we consider a good soil 
and in good condition, but not at all rich in nitrogen. 
We imitated field conditions by taking 3,000 pounds of this soil 
from the field and made a bed of it where we could watch it, water it 
and keep the weeds out. We built a fence around it to keep animals 
off and to let the children know that we did not want them to go on it. 
We watered it with pure water of which we added only enough to 
keep the moisture in the soil around 15 percent. We protected our bed 
from being washed by heavy rains by fixing it so that we could cover 
it with canvass if it should rain, but the bed was open to the sun and 
air just as it would have been had we left it in the field. While we did 
not want to have our soil washed out by water from above we did not 
want any water to come up from below and bring a lot of salts up with 
it, so we put a tight board bottom under our bed with tight board sides 
to it. We added nothing to this soil but water. The plants had to get 
along on that soil. We even banked up the earth a little way from the 
bed to prevent any rain-water washing other dirt into it and to catch 
any blowing sand as far as possible. We analyzed the soil as we put it 
into the bed and every fifth day after that for 40 days. At the end 
of this time we found that it had more nitrogen in it than at the be¬ 
ginning, so much more that every million pounds of this soil had gained 
36 pounds of nitrogen, which would be equivalent to 216 pounds of 
sodic nitrate if it were all converted into this form. Further, we found 
that the nitrates themselves had increased by 94.8 pounds for each mill¬ 
ion pounds of the soil. Our bed was 6 inches deep, so we had the 
equivalent of 198.6 pounds of sodic nitrate formed in the top 6 inches 
of this soil which weighs about 2,000,000 pounds per acre in 40 days. 
There was just about the same gain in the first and second 3 inches, 
and while this will be different in different cases, we may state the 
results for the acre-foot, which would be 397.2 pounds calculated as 
sodic nitrate. We did not pick a particular 40 days in which to 
make our experiment, so we have a fairly good right to assume that 
the same results would be obtained for any other 40 days of the season. 
The results at the end of the five-day periods may indicate whether 
this assumption is justified. 
These results show that the increase was not uniform, but that there 
was sometimes a falling back, though it never got back in our experi- 
