The: Fixation of Nitrogen. 29 
and a half feet deep in a low spot in the field, and while the ground 
was wet, there was no free water. It is very probable that the water 
table in this land varies exceedingly from place to place, indeed 
it is very probable that one might choose a place and dig a hole 
twelve or more feet deep and find no portion of it wetter than the 
top six inches, possibly not as wet, and at another point encounter 
water within three feet or less of the surface; further, these points 
may be dose together in the field. A sample of surface soil with 
its alkali was taken at the point where I dug the hole four and a 
half feet deep; this was mixed with samples of like soil from other 
parts of the field. This sample is so rich in nitrates that the aqueous 
extract from two grams of it gives a strong reaction for nitric 
acid. In 1907 the extract of the soil gave none. There are many 
square miles of such lands. The following analysis is to be com¬ 
pared with analyses of Laboratory Nos. 622 and 632. This land 
was already seeped in 1907, almost if not quite as badly then as 
now. The water-soluble in sample No. 1070 equalled 18.176 percent. 
ANALYSIS XXXIII 
Water-Soluble 
laboratory 
No. 1070 
Surface Soil 
May 2, 1911 
Percent 
Calcic sulfate . 21.104 
Magnesic sulfate .15^766 
Potassic sulfate . ’ 2.391 
Sodic sulfate . 1 676 
Sodic chloricl . 5S.263 
Sodic nitrate. 0.51S 
Iron and Aluminic oxid.’ " ’ o!o52 
Silicic acid .! 0^230 
100.000 
The percentage of sodic nitrate in this analysis is not large 
compared with some of our samples, but compared with the quan¬ 
tities present in 1907 it is quite as striking as the changes in the 
appearance of the land itself which was then the uniform gray 
of our adobe soils, now it looks as though it had been irregularly 
moistened with a heavy crude oil and though the large quantities of 
salts present are not favorable to an abundant development of 
nitrates we now find nitrates present at the rate of one and nine- 
tenths tons per acre-foot where, four years before, we found none. 
Case No. 9—1 visited this orchard for the first time May 
18, 1910. The age of the trees still living was twenty-eight years. 
No disease had appeared in the orchard till the season of 1909. 
During this season about two and one-half acres of the orchard, 
two hundred trees, showed serious trouble and died in about six 
weeks. These trees had been removed from the orchard at this 
time, May 18, 1910, and used to stop the washing away of the 
