16 
COLORADO EXPERIMENT STATION 
nitrates. The area of the original tract was forty acres and previous 
to 1911, from seven to eight acres had died and the trees had been 
taken out. In 1911, this part was sown to oats, but the stand was very 
unsatisfactory. The mealy ridges of the irrigating furrows were barren, 
and what little growth occurred took place in the bottom of the furrows 
where the water appeared to have reduced the nitrates to a point of par¬ 
tial tolerance. Nothing was planted here the next year. The burning 
was general over the remainder of the orchard in 1912, but the attack 
seemed to have been cencentrated upon two rows of trees next to the 
outside row on the east side. Practically every one of these was so badly 
burned that no green color was left to the foliage and the apples in Sep¬ 
tember were not more than two-thirds grown and badly shriveled. Judg¬ 
ing from the hardness of the ground and the aspect of the orchard as a 
whole, it had been neither irrigated nor cultivated that season and was 
suffering from general neglect. My sample consisted of the surface- 
four inches taken between two burning trees. The soil is a clay loam 
and was very hard and dry. There was no brown color visible, due, 
presumably, to the fact that the ground was too dry for the development 
of the Azotobacter pigment. It contained 6 p. p. m. of nitric nitrogen 
and 202 p. p. m. of chlorin. 
Sample No. 88 .—Of all the soils which we have had under observa¬ 
tion, none has offered a better opportunity for watching the develop¬ 
ment and lateral movement of the high nitrates than this one. The 
wi iter’s acquaintance with the area dates from 1909 when all that was 
left of a twenty acre orchard was parts of six rows of trees on one 
side next to a ditch. The whole tract involved is forty acres, twenty of 
which was in alfalfa prior to 1907 and the balance in bearing apple 
trees. In 1907, barren spots began to appear in the alfalfa and brown 
patches to develop in the orchard. Soon the trees began to show the 
burned leaf margins which we have come to associate positively with 
excessive nitre, and a large number died. Here, as is so often the case, 
a few trees in the interior of the orchard succumbed first, and from 
these as a focal center, the destruction spread rapidly in all directions. 
The attack was so severe and the progress so rapid that by the spring 
of 1909, all of the alfalfa had been killed and at least fifty per cent, of 
the trees. During 1909, the remainder of the trees died except parts of 
six rows. During 1910, the three inside rows of these were killed. In 
1911, the two inside rows of the remaining three travelled the road of 
their fellows, and the lone outside row bade fair to follow, for several 
of its members were burning. When I next visited the place to take 
the present sample in the fall of 1912, not one tree was standing. All 
had died save three, which the owner had taken pity on and cut down. 
These three were still green; the foliage was not burned, but the leaves 
were small and scattering. I first saw the orchard in 1909, and at that 
time the whole central portion from which the trees had been removed 
was as brown as could be; in fact, almost black. This color did not 
extend into the six rows which were still alive beyond the very inside 
row. The next year it moved in four rows, but beyond this, the color 
and physical condition of the soil were normal to all appearances. By 
