Bulletin 1356, U. S. Department of Agriculture 
tion of clay in this soil to give it a loamy cohesiveness which may 
cause puddling when plowed in a wet condition. The subsoil is a 
mottled blue and yellow clay, very plastic and extremely impervious. 
There is no movement of water through this subsoil in situ. TThere- 
ever this clay is properly used in the construction of canal banks and 
field levees seepage is so small as to be negligible. 
TOPOGRAPHY 
The flatness of the surface of this area permits the application of 
irrigation water over large tracts with a limited number of field 
levees. It also permits the 
construction of low broad 
levees, which offer no bar- 
riers to the use of heavy 
machinery in the prepara- 
tion of the soil and in har- 
vesting the crop. 
Prairies that are com- 
paratively level extend 
southward from approxi- 
mately the central part of 
Calcasieu. Allen, and Evan- 
geline Parishes to the 
marshes bordering the Gulf 
of Mexico. In the western 
part of St. Landry and 
Lafayette Parishes and the 
extreme eastern part of 
Vermilion Parish the prai- 
ries slope to the southwest. 
Within this area the alti- 
tude varies from a few feet 
to 47 feet above sea level. 
As a rule the slope is suffi- 
cient for good drainage by 
gravity, but not too great 
to prevent the holding of 
irrigation water on large 
tracts by low field levees. 
PRECIPITATION 
Fig. 2 
The quantity of water 
required for the irrigation 
of the rice crop is de- 
pendent upon the precipitation within the area under cultivation 
and upon the watershed of its streams. The average annual precipi- 
tation recorded at the Kice Experiment Station. Crowley. La., for the 
period from 1910 to 1922, inclusive, is 56.33 inches. For the same 
period of years Jennings, La., had an average annual rainfall of 
56.60 inches; Lake Charles. La., 61.57 inches; and Lakeside, La., 
64.51 inches. This precipitation as a source of supply is sufficient to 
meet the water requirements of the crop and is fairly Veil distributed 
throughout the year. 
2. — Diagram showing the maximum, minimum, 
and average rainfall at the Rice Experiment Sta- 
tion. Crowley. La., for each month during the 
14-year period from 1910 to 1923, inclusive 
