THE NITRIFYING EFFICIENCY OF CERTAIN COLORADO SOILS 
21 
a section of the country where no trouble was ever experienced from 
high nitrates until 1911. Almost every other part had had its trials but 
this region appeared to have been favored. As I was driving past this 
orchard one afternoon in October of 1911, I noticed some thirty trees 
in one corner that were dying unquestionably from too much niter. 
These were the only trees affected in this way that could be found 
any place in the neighborhood. The soil is a clay loam and it was 
rather moist from a recent shower, so it was difficult to determine 
the presence of the brown color. I visited the place again in July, 
1912, and found that the burning had spread over the entire district 
embracing, I should judge, eight to ten square miles. Practically 
everything in the way of apple trees was suffering. The owner of 
the place told me that the burning had all developed since the last 
irrigation which was begun on Sunday, June 30th, and was continued 
until the following Wednesday. About three days after he took the 
water off, he had observed the dark brown stain on the irrigating 
furrows and in about one week the trees began to burn. That is to 
say, one week was required for the nitrates, which were carried from 
the surface to the feeding zone of the apple roots, to produce the 
physiological effect on the foliage which we have designated as burn¬ 
ing. 
The soil was hard and dry at the time the sample was taken; there 
was no brown color visible and judging from the physical condition 
of the soil, it had received little cultivation and irrigation during the 
summer and fall of 1912. Nitric nitrogen amounting to 20 p. p. m. 
and chlorin to 65 p. p. mi. were found. 
Foreign Soils 
Sample No. 52. —Ohio. Received March, 1913; clay loam; moist; 
corn field; nitric nitrogen 7 p. p. m.; chlorin 8 p. p. m. 
Sample No. 53. —Georgia. Received March 10, 1913; red gravelly 
loam,; oak and pine forest; wet when sent; nitric nitrogen 5 p. p.m.; 
chlorin 78 p. p. m. 
Sample No. 54.—Washington. Received March 9, 1913 ; dark 
loam; upland soil from an orchard; typical of the river bench soil' 
common to that locality; moisture good; nitric nitrogen 5 p. p. m.; 
chlorin 40 p. p. m. 
Sample No. 55.—Virginia. Received March 10, 1913 heavy clay 
from an orchard; sample wet due to heavy rains at the time 
soil was collected; nitric nitrogen 9 p. p. m.; chlorin 74 p. p. m. 
Sample No. 56. —Oklahoma. Received March 17, 1913; sandy 
loam; cotton in 1912, dry; nitric nitrogen 11 p. p. m.; chlorin 8 p. p. m. 
Sample No. 57.—North Carolina. Received March 19, 1913; 
light sandy loam; sharp sand with little organic matter; water melons 
1912; moisture good; nitric nitrogen 7 p. p. m.; chlorin 10 p. p. m. 
Sample No. 38. —Texas. Received March 18, 1913; dark sandy 
