Bacteriological Studies of the Fixation of Nitrogen. 7 
in the near future. In this connection, I may say that it is my purpose 
this coming season to plant several foreign grasses, reputed to be heavy 
nitrogen feeders, on high nitre soils with the expectation of securing 
some crop which can utilize the nitrogen. 
In order that the reader can have a more definite idea of the 
amount of nitrates which have been found in some of these once arable 
soils, I am giving below a few figures on this point which have been 
furnished to me by Dr. Headden, to whom I am indebted for the soil 
analyses and many of the soil histories contained in this bulletin. 
By way of comparison, I may say that an average amount of ni¬ 
trate for our cultivated fields is from .000626 to .002005 P er cent. 
TABLE No. 1. Nitrates in certain Nitre Soils. 
Source 
Material 
examined 
Percent 
water 
soluble 
Percent 
nitrates in 
water 
soluble 
Percent 
nitrates in 
air dried 
soil 
Black spot in 
barley field. 
Surface soil two 
inches 
13.4 
41.859 
5.628 
Young orchard 
Surface soil 
22.466 
29.114 
6.54 
Young orchard 
Surface soil two 
inches 
8.23 
8.173 
.673 
Alfalfa field 
Top soil five 
inches 
7.78 
33.06 
2.571 
Oat field 
Surface soil two 
mcnes 
5.42 
50.221 
2.722 
Orchard 
Top soil 12 inches 
6.51 
43.57 
2.837 
Corn and rye. 
Surface soil 
4.67 
7.352 
.342 
Old orchard 
Surface soil 
6.65 
5.746 
.382 
These figures may mean more when I say that one of the above 
samples, which carried 2.873 P er cent of nitrates in the surface foot, 
contained nitrates corresponding to 113,480 pounds, or 56.74 tons per 
acre foot; in another sample, taken to a depth of five inches, the area 
involved being about eight acres, sodic nitrate corresponding to 
344.000 pounds or 172 tons was found in the surface five inches; in 
the top four inches of another eight acre tract, the equiva ent of 189, 
971 pounds or 95 tons was found. 
With such quantities of nitre in the soil as these figures indicate, 
it seems hardly necessary to look elsewhere for an explanation of the 
death of our trees and crops. 
Because of other investigations which were already under way, 
I was not able to take up this very interesting question until recently, 
except to go on occasional, hurried field trips into the districts in¬ 
volved. Here, I saw all that had been described to me, and, I must 
confess, intensified and more serious than I had imagined. 
A very natural explanation for the accumulation of these nitrates, 
and one which may have suggested itself to the reader, would be the 
