Irrigated Agriculture in the San Luis Valley ii 
DRAINAGE. 
The best evidence available shows that there are approximately 
three-fourths of a million acres needing more or less artificial 
drainage. Possibly 25,000 acres are now provided with drainage 
systems. A large amount of the seeped land is damaged by irriga¬ 
tion—largely sub-irrigation. A small amount has been damaged 
by the flow of springs and artesian wells. 
Owing to the great length of the slopes and their uniform 
grade drainage systems to be successful will require large districts 
and community effort. Drainage operations now being carried on 
are successful enough to warrant the statement that satisfactory 
drainage presents no seriously difficult engineering features. It 
does demand, however, widespread community co-operation. 
GENERAL FARMING CONDITIONS. 
The soils of the Valley have already been discussed specifically. 
Soil conditions for farming purposes can be summarized by stat¬ 
ing what actually prevails. The great majority of the soils are 
sandy loams and gravels, underlaid by gravel. There are heavy 
soils in the northern part of the Valley and along the flood plains 
of the streams in other portions. These heavier soils often pre¬ 
sent very peculiar local conditions which are difficult to deal with 
but from the standpoint of the farming of the Valley they are rel¬ 
atively unimportant, because the area is not very great. 
The gravelly subsoils where drainage is good, make the mois¬ 
ture situation acute since they usually cause surface soils to dry 
out readily, especially if the gravel comes close to the surface. Such 
conditions will require frequent watering in farming practice. 
* A general lack of organic matter or vegetable matter affects 
the Valley soils, except the heavier and recently formed soils along 
some of the stream courses. Farming practice which aims to main¬ 
tain production and to increase the fertility of these soils must in¬ 
clude some scheme for incorporating vegetable matter (commonly 
called organic matter) with the soil. Owing to the altitude, the 
seasons are short and the nights cool so that rotting of organic 
matter is a slow process. This has led to the general impression 
that manure and other organic matter cannot be rotted in these soils. 
This is a mistaken belief. If the organic matter or manure be 
thoroly chopped to pieces with a disk harrow and mixed with 
the surface soil, it will be well incorporated with the soil when the 
plowing and harrowing operations are performed. The pulverized 
organic matter readily rots and mixes. 
The general farm practice of the Valley is to plow too shallow. 
Deep plowing immediately before seeding will usually delay the 
