The Fixation of Nitrogen. 95 
nitrification as generally understood, but their occurrence in unusual, 
detrimental and fatal quantities, over areas measured by the square mile 
of territory. 
The nitre question presents a distinct problem whose relation to the 
problems of alkali, seepage and drainage is not so intimate as is indicated 
by the statements made in Bulletin 15 5. 
The statements of Bulletins 155 and 160 in regard to the cause of the 
“brown spots,” the character of the salts present, their fatal effects upon 
vegetation and their extremely deleterious action upon the soil are cor¬ 
roborated. 
The spread of the trouble during the year 1910 was very marked. 
The intensity of the attacks has increased rather than abated. 
Some instances of a very rapid development combined with extremely 
intense action have been observed. In one fourteen-year-old orchard not 
less than twelve acres of trees, apple, plum, pear and cherry, together 
with currant bushes and other small fruit have been killed in less than a 
year. The water table in this land was not, at any time, near enough 
to the surface to do any damage. 
No single instance of the death or eradication of a brown area, a 
nitre spot, has been observed; but the interior of such areas has been 
found so excessively rich in salts that the ground has become barren, even 
of the azotobacter flora. 
This deportment of the bacteria suggests the probability that the land 
may again become fertile after a few years, in fact, varieties of Atriplex, 
saltbushes, are already taking possession of land which has been devoid 
of vegetation for several years. 
The drainage in several of the cases given is excellent, in other cases 
drains have been laid for periods of from one to five years without pre¬ 
venting the formation of nitre areas. 
Trees badly affected by this trouble show almost no recuperative 
power, probably due to the continued excessive supply of nitrates in the 
soil, possibly to the severe toxic action of the nitrates. So afr as our ob¬ 
servation goes both factors seem to be involved. Slightly affected trees 
may recover but no badly affected tree has been observed to do so. 
The generally observed change in the soil, indicating danger to the 
trees, is a turning brown of the surface which is expressed by the state¬ 
ment that “The soil turned brown or black and the trees died.” 
The samples of brown soil have, without exception, contained ex¬ 
cessive quantities of nitrates. 
The color is not due to the nitrates nor to sodic carbonate or black 
alkali proper but to the development of pigments by the azotobacter. 
This applies to the soils here described. Some soils may have a brown 
color due to other causes. 
This condition is usually preceded and accompanied by a mealiness 
of the soil, often described as ashy. There is usually but little or no 
efflorescence on such soils, though it sometimes occurs. 
The time required for the killing of a tree varies with the virulence 
of the attack, in bad cases from four days to two weeks. Slightly affected 
trees may linger a long time. 
These areas may occur in perfectly drained land, situated m the 
midst of land which shows no abnormal quantities of nitrates. 
In one case, and possibly in others also, injury to many trees followed 
the application of w T ater, probably due to the washing of the nitrates down 
into the soil. , . , . 
The river waters used for irrigation, whether stored or not, contain 
no unusual quantities of nitrates. 
The ordinary white alkali that commonly occurs in these sections is, 
for the most part, free from nitrates, but the brown and white areas 
frequently overlap. 
The ground waters, unless derived from nitre areas, aie tiee ti° n 
nitrates.and these nitrates cannot be accounted for by the evaporation of 
such water from the surface of these areas. 
