RECLAIMING NITRE SOIL IN THE 
GRAND VALLEY 
By E. P. SANDSTEN 
The experimental work of Dr. Headden and Professor 
Sackett* of this Station has proven conclusively that the origin 
of nitre, often called black alkali, so abundant in many of our 
Colorado soils, is due to the activity of the nitre-forming organ¬ 
isms. The nitre is not confined to any particular section of the 
State, but occurs in almost every district and in all types of soil. 
A study of soil management, especially in the orchard areas 
of the Grand Valley, has led the writer to conclude that the ex¬ 
cessive accumulation of nitre is greatly increased by clean culti¬ 
vation, as extensively practiced by the fruit growers. 
It is a well-known fact that in most semi-arid soils there is 
little or no fermentation of organic materials, due to the action 
of prolonged sunshine, light rainfall and dry atmosphere. This, 
coupled with the presence of a high percentage of alkaline salts, 
forms ideal conditions for the activities of the nitre-forming 
organisms. The additional fact that nitre rarely occurs in in¬ 
jurious quantities in soils on which alfalfa is grown continuously 
for a long series of years, would indicate that land kept con¬ 
stantly in clean culture furnishes the best conditions for the nitre¬ 
forming organisms. 
The orchard survey of Grand Valley, made by the Horticul¬ 
tural Department, reveals the fact that more than one thousand 
acres of bearing orchards, and orchards just coming into bear¬ 
ing, have been destroyed by nitre during the last few years, and, 
in addition, a considerable portion of the remaining orchards in 
the Valley are showing signs of nitre poisoning. 
These observations led the writer to undertake some work in 
Grand Valley to reclaim land that had become barren because of 
excessive nitre, and also to check the process of nitre-formation 
in orchards that were still healthy and productive, but which 
showed signs of nitre poisoning. 
The presence of excessive nitre in the soil is readily distin¬ 
guished by the characteristic reddish-brown discoloration, and the 
mealy or powdery texture which always accompanies this trouble. 
In the orchards, the presence of nitre is also readily distin¬ 
guished by the appearance of the foliage of the trees, especially 
the foliage on tender growing shoots. The margins of the leaves 
*See Bulletins Nos. 155, 160, 178, 179, 184, 186, 193. 
