The Fixation of Nitrogen. 41 
this orchard showed in August and September more or less burning 
and here and there a tree wholly succumbed. Many trees, how¬ 
ever, were only severely injured, either by having one or more 
limbs entirely killed or the extremities of the branches killed back 
varying distances. As yet this section of the orchard does not 
show the burning badly at all; it is too early and the trees have 
not had a liberal supply of water. 
The western part of this orchard was rather bad, and many 
trees showed burning last year, but the burning did not take place 
till the latter part of the season, from mid-summer till autumn. 
This year, however, many trees that came into full leaf in early 
May had already been killed by the thirtieth of the month. I visited 
this orchard on the second and again on the thirtieth of this month 
and while I have seen other orchards destroyed quickly I have no¬ 
where seen anything surpassing this in the extent of the injury and 
the rate of its accomplishment. The ground water was four and 
three-quarters feet below the surface. The surface soil was dry 
but brown and mealy. The disc had cut about three inches deep 
and the sides and bottom of the cut looked as though crude oil had 
been uniformly distributed over them. Sample No. 1063 was 
gathered from the surface of this ground on March 28, and was 
taken to a depth of two or more inches. It was a composite 
sample made up of smaller samples from several places. Sample 
1072 was likewise a composite sample taken from the sides and 
bottom of the cut made by the disc. These samples represent the 
salts soluble in water and contained in the top two inches of the 
soil, where the trees are now dying very rapidly, and we see that 
they agree in showing 6.158 and 6.197 percent of such salts, 
47.233 percent of the former and 35.556 percent of the latter 
being composed of nitrates. Calculating the nitrates present in 
the top two inches of this soil, we obtain 9.6 tons per acre for the 
sample taken in March from the surface soil and 7.6 tons for the 
sample taken in May from the sides and bottom of the disc cuts 
or furrows, or calculated on the acre-foot, 58 and 44 tons respec¬ 
tively. The ground where the samples were taken is lower than 
a portion of the orchard but the ground is still so sloping that we 
cannot explain the presence of this large quantity of nitrates by 
supposing them to represent the washings from the rest of the 
orchard. 
Plate II shows the condition of some of the trees in this 
orchard on June 23, 1911. The upper photograph, Fig. 1, repre¬ 
sents a tree which at this time showed no effects of the nitrates. 
The lower one, Fig. 2, represents a tree which developed a full 
foliage in May and was dead at the time the photograph was 
taken, June 23, 1911. These two trees do not stand more than fifty 
or sixty feet from one another. The only reason why trees even 
