26 
SOILS AND ALKALI. 
in question is used for irrigation, what amount of alkali 
would accumulate near the surface ? Dr. Hilgard, of Cali¬ 
fornia, says that ten inches of water is the usual estimate 
of what is required in a year to perfect a crop; if this be 
true, 61 gallons of water per square foot is equal to 10 
inches depth of water. The solid contents of the well water 
was 84 grains to the gallon; this quantity, upon evapora¬ 
tion, would leave 84x6f = 560 grains, or a little over 1J 
ounces of alkali on each square foot. It is known that in 
Colorado much more water is used to raise a crop than in 
California. It can then be readily seen that this operation 
could not be repeated many years without disastrous re¬ 
sults. Sufficient experiments have not been tried to draw 
any very accurate conclusions as to the extreme limit of 
the per cent, of alkali that a soil can contain and be pro¬ 
ductive. A California soil was productive that contained 
over two ounces of carbonate of soda to the cubic foot, and 
had, possibly, three or four ounces of other ingredients, 
making, in all, over six ounces to the cubic foot. The 
alkali is caused by the yearly evaporation of enormous 
quantities of water, whose dilute solutions have been al¬ 
lowed to concentrate upon the soil. These facts should 
impress upon the farmers the importance of providing 
proper drainage for their lands, so they will not be com¬ 
pelled to abandon, in many cases, the most valuable and 
productive portions of their farms. 
CONCLUSIONS. 
To summarize, the analyses of Colorado soils and 
waters seem to justify the following conclusions: 
1. That the physical properties of the soil influence 
its fertility. 
2. That the fertility of a soil is not always thoroughly 
shown by chemical analysis. 
3. That the fertility of a soil depends largely upon 
