IRRIGATION WATERS AND THEIR EFFECTS. II 
pounds and a like quantity, an aere-foot, of drain water contained 
895 pounds. The water in the ground contained 868 pounds of 
sodic sulfate while drain water contained 168 pounds in an acre- 
foot, Evidently the sodic carbonate has passed out of the soil 
much more freely than the sulfate. If the sodic carborate were 
retained unchanged by the soil the result would be most unfor¬ 
tunate. This sodic carbonate is none other than “black alkali.” 
We will take an irrigation water, such as we found that of War¬ 
ren’s lake to be in 1902, an excellent irrigation water with only 
26 grains of mineral matter in each imperial gallon. We find in 
this 88 pounds of sodic carbonate per acre-foot, or the application 
of 20 acre-feet would add 1700 pounds of anhydrous sodic carbon¬ 
ate to each acre of land. Experiments made some years ago led 
me to conclude that if there were as much as 1750 pounds of 
sodic carbonate per acre, taken to a depth of one foot, it would 
under ordinary conditions kill young plants such as beets, etc. 
If the soil retained the sodic carbonate within a foot of the surface 
without changing it in any way the result would be that the soil 
would be rendered perfectly useless. The soil fortunately does 
not retain this, the most dangerous of alkali salts, but permits its 
passage rather readily, and its eventual removal by the drain 
water. 
These properties of the soil fortunately prevent to a great 
measure, the accumulation of the more injurious salts added with 
the application of seepage water, or such as have been stored and 
become more or less heavily charged with soluble salts. 
The water used for direct irrigation, that is, water taken directly 
from mountain streams does not carry any notable quantity of 
plant food. Water that has been stored in reservoirs, especially 
such as receive off-flow, waste and drainage waters, may carry more 
potash, but with it a very large amount of other salts. These salts 
are not very intense in their action on vegetation and are dissemin¬ 
ated through a very large mass of soil and the most injurious one 
of them, sodic carbonate, is not retained by the soil. In other 
words, is rather readily permitted to pass into the ground water 
and thence into the drain waters, if drains have been established. 
The changes effected by the irrigation water after it has 
entered the soil and before it sinks below the reach of the plants 
or passes out of the soil, present an interesting subject of study. 
The general and important question in this connection is, how ef¬ 
ficient an agent it is in bringing plant food into an available form. 
Perhaps an equally important question is, what part does it play 
in changing deleterious salts into less injurious ones or in remov¬ 
ing them from the soil. These questions are much more easily 
s uggested than answered. It is conceded that food to be available 
to plants must be soluble. It, however, does not necessarily fol- 
