14 Colorado Experiment Station 
found at a less depth in other places. This ground-water carries 
about 260 parts of “black alkali" to the million parts of water. It 
mixes with the river-water added in sub-irrigating the land and 
brings the “black alkali” with it. This went on for a number of 
years till the land became so rich in “black alkali" that crops were 
no longer successfully raised and this is the condition today 
throughout this section of some 400,000 or 500,000 acres. Most 
of the people of the valley still think that sub-irrigation is a good 
system. A few are convinced that it is not. 
CONDITIONS CAN BE CORRECTED 
The important questions for the valley are, Can this condition 
be corrected? and, Is it feasible to correct it? 
I answer “Yes” to both questions, but there are difficulties 
in the way. 
The conditions are very bad. There is no hope of removing, 
in any way, the great reserve supply of sodic carbonate as indi¬ 
cated by the richness of the artesian waters in this “black alkali”. 
This section of the valley is full of this water, and the deeper we 
go the richer is the water in “black alkali”. The more of this water 
we bring to the surface or allow to leak into the upper strata out 
of uncased wells, the worse we are off. No man can tell how long 
it has taken to bring about these conditions, but they have already 
existed from the very early history of the valley and, so far as we 
are concerned, they are as permanent as the mountains inclosing 
the valley. The water has probably never run out of this section 
of the valley and the deep artesian waters never will, if we measure 
time in terms of human lives. 
We do not care how these conditions have come into existence, 
the question is, To what extent can we modify them? Can we 
modify the surface portion of this land so that we can raise crops? 
GYPSUM WILL CONVERT <( BLACK ALKALI” -INTO 
HARMLESS “WHITE ALKALI” 
It is well known that gypsum, sulfate of lime, will convert 
this “black alkali” into “white alkali”, which is so good as harmless 
compared with the black. By the application of this gypsum we 
can mitigate the evil, but this will be a difficult problem if we 
continue the practice of sub-irrigation which brings the “black 
alkali” up; it will be necessary to change the system and wash 
the “black alkali” with the gypsum down. The people have found 
out that, at the present time, about the only thing they can do to 
make any headway against the present conditions is to dike and 
flood the land. There is usually space enough between the per¬ 
manent water-plane and the surface to permit them to better the 
