Irrigated Agricueture in the San Luis Vaeeey 15 
cessfully. Some planning for the future was necessary so that the 
organic matter in the soils might be built up. Deep plowing and 
frequent cultivation were needed for success, in addition to a great 
deal of hand labor. These requirements were not met in the Val¬ 
ley, and the beet industry has been a failure. Disease has made 
potatoes an uncertain crop. They were formerly staple. 
alfalfa. 
It was, formerly supposed and quite commonly asserted, that 
alfalfa could not be successfully grown in the San Luis Valley, but 
the folly of this belief has been amply demonstrated in the past few 
years, and it is now known that the crop can be grown practically 
everywhere in the Valley. Fields of some years’ standing may be 
found in nearly every section at the present time. From Del Norte 
on the west and Hooper and Mosca on the east; from Saguache 
and Moffat on the north to Antonito on the south, and San Luis. 
San Acacio and Eastdale on the southeast, there are successful 
fields of alfalfa. Many of the failures in the past have been due 
to a lack of understanding of proper methods of handling the crop 
and to improper varieties. 
The altitude of the San Luis Valley is very high and the ex¬ 
tremes of temperature and moisture are consequently great. The 
southern types of alfalfa and much of the so-called common alfalfa 
are not likely to prove successful because of their inability to stand 
the winter climate and the dry cold, windy springs. 
Alfalfa is a deep-rooted crop. Where the root room is lim¬ 
ited by subsoil water, the common alfalfas will not survive. The 
so-called hardy or northern types will grow under these conditions, 
but the reduction of root room causes them to feed heavily upon 
the surface soil, and all except exceedingly rich soils will soon be 
exhausted.. Alfalfa is commonly supposed to be a soil improver, 
renovator or fertilizer. Under proper conditions this is absolutely 
true, but it is also true that of all the crops grown in the Valley 
alfalfa is one of the heaviest feeders upon soil fertility. It may be 
expected, therefore, that on those soils where the rise of sub-soil 
moisture is such as to develop a very heavy shallow root system, 
the crop will eventually tend to exhaust the soil fertility. Many 
of the Valley soils, as has already been shown, have sandy and 
gravelly subsoils. On such soils, when the subsoil water is allowed 
to recede fif it does recede') the mass of roots in this narrow zone 
at the surface finds difficulty in securing moisture enough for the 
plant to subsist upon. Growing upon these porous soils the crop 
is unable to put roots down into the gravelly layer fast enough to 
get the water needed for growth and the thick mass of roots in 
