18 
COLORADO EXPERIMENT STATION 
lence of the attack centered in one corner and resulted in the death 
of every tree on two and one-half acres save a few in the outside fence- 
row along an irrigating ditch. This meant the loss of approximately 
two hundred and fifty bearing trees. During the last two seasons, the 
trouble has become generally distributed over the south half, but it ap¬ 
pears to be very much less active than in the preceding years. The 
trees exhibit some burning, and the leaves and fruit are undersized, 
with a suggestion of premature ripening, but the death rate does not 
begin to be as high as in 1910-1911. My sample consisted of the sur¬ 
face four inches of sandy loam taken between two burning trees on 
the edge of the two and one-half acres where everything had died. No 
brown color was in evidence, although the soil was moist. The nitric 
nitrogen present amounted to 13 p. p. m. and the chlorin to 140 p. p. m. 
Sample No. pi.—During the summer of 1910, while looking over 
a large orchard for indications of niter, I came upon three trees near 
to one another whose leaves were considerably burned. The inference 
was that the same causal factors were operative here as elsewhere, 
although no nitrate determinations were made at the time. A sample 
of the soil was taken for my nitrogen fixation experiments, and better 
than 11.00 m. g. of nitrogen were fixed with 1.5 g. of mannite. I did 
not see the orchard again until the fall of 1912, and I must confess 
that I was very much surprised to be unable to find a single tree affect¬ 
ed where I had noted them before. In place of the dwarfed, sickly 
growth with many brown leaves, I found the trees unusually vigorous 
and free from burning. Many had sent out new shoots over three feet 
long; the foliage was fully developed and of an excellent color. Con¬ 
fronted with such an unexpected condition of affairs, I set out at once 
to find the manager and to ascertain, if possible, an explanation of this 
remarkable rejuvenation. According to the owner’s statements, one 
hundred and fifty-six trees were in a serious condition with niter 
symptoms in 1911, and realizing the immediate need of some extreme 
measures to save the trees, he plowed the whole orchard twelve to 
fourteen inches deep that fall, and in the spring of 1912, he dynamited 
the two acres where the trouble seemed to be localized using one-half 
stick of dynamite placed midway of the rows for each four trees. 
Following this, he turned on a big head of water and washed out the 
soil as thoroughly as can be accomplished by such a procedure. The 
blasting had loosened the soil to a considerable depth so that the water 
penetrated it very readily, and any nitrates that had accumulated in the 
surface layers were doubtless reduced very materially. Added to the 
benefit derived from this source was the greatly improved physical 
condition of the soil, which must have encouraged new root develop¬ 
ment. This last factor was undoubtedly responsible for the thriving 
condition of the orchard. Although I did not locate any burning trees 
myself, Mr.- stated that there were a few, not to exceed six, 
whereas in 1911 there had been one hunded and fifty-six. He told 
me that the results of his blasting experiment had been so gratifying 
that it was his purpose to apply the same treatment to the remainder 
of the orchard before another season. 
