8 
COI^ORADO ExPE:RIMI:nT STATION 
of alkali are encountered which is mostly composed of sodium sul¬ 
phate and sodium chloride. Some magnesium sulphate also occurs. 
In the vicinity of the alkali lakes, in the eastern part of the 
Valley, there is an occurrence of some black alkali or sodium car¬ 
bonate as well as some sodium bicarbonate. Outside of this small 
locality the alkalis of the Valley are mostly the so-called white al¬ 
kalis and are occasionally in sufficient quantities to be injurious 
to vegetation. They come to the surface when the land is water- 
logged or seeped. Probably more damage is done by seepage in 
many of the wet alkali sections than by the white alkali itself, al¬ 
though the percentages sometimes run high. 
With few exceptions, the soils of the Valley are deficient in 
organic matter, the incorporation of which is one of the big prob¬ 
lems of farming and successful soil management. 
IRRIGATION. 
Probably the first irrigation in Colorado was by the civiliza¬ 
tion which gave rise to the cliff dwellings still extant in the extreme 
southwestern portions of the state, but the first modern irrigation 
was probably in the San Luis Valley. The first development was in 
the extreme southeastern part of the Valley and was small in com¬ 
parison with the present irrigated acreage. Some irrigation 
systems now in use date back as far as the early fifties, but until 
1880 development was slow. The ditches were taken out by 
individuals or by a few farmers associated together. During the 
period from 1880 to 1890 a majority of the present ditches of the 
Valley were constructed. Little was done from 1890 to 1905’ but 
since then new systems have been built and many of the older ones 
improved by the construction ol reservoirs and by ditch betterments. 
There are at present in the Valley approximately 1,100 ditches 
with adjudicated water rights. These aggregate an appropriation 
of 15,873.82 second-feet, while about a hundred other ditches have 
unadjudicated claims for water. There are about 2,000 miles of 
ditches and principal laterals. Authorities differ as to the area of 
the land irrigated in 1914, this being variously estimated at from 
500,000 to 790,000 acres. Five hundred thousand acres is perhaps 
a conservative approximation, having been arrived at by checking 
up the records of agents in the field during that season. It is be¬ 
lieved that the number of acres which can be irrigated is approxi¬ 
mately 800,000. 
During the early days of irrigation development in the Valley 
nearly all of the water used was secured by direct diversion from 
the streams, but during the past few years seventeen reservoirs 
with an aggregate capacity of over 260,000 acre-feet have been 
