RELATION OF SOILS TO IRRIGATION. 21 



them that the best results are often obtained by western 

 irrigators. 



Gumbo and Loam. Gumbo soil is a term applied 

 to a class of heavy soils prevalent in the South, having a 

 greasy feeling and a soapy or waxy appearance. The 

 particles that compose the soil are very small, less than 

 one one-hundredth of an inch in size, and there is but 

 very little true sand present. These soils are always 

 rich in alkali, particularly the potash compound. It is 

 this potash that gives it the soapy appearance and greasy 

 feeling. They fail to scour the plow because of the 

 absence of sand, and the extreme fineness of the particles. 

 No cheap chemical can improve these soils, but continual 

 cropping gradually causes an improved condition by 

 the gradual removal of the excess of potash. They are es- 

 pecially adapted for grass and hay crops. Gumbo is 

 more impervious to water than most soils are and as a rule 

 requires much less irrigation. Loam soils comprise 

 those molds ranging between sand and clay and possess- 

 ing more or less each of these two constituents. They 

 constitute what may be termed the happy medium, and 

 are really the most desirable kinds of earth on which to 

 ply the irrigator's art. The term loam is a most indefi- 

 nite characterization on account of the various constitu- 

 ents which it contains. For instance a heavy clay 

 loam has but from ten to twenty-five per cent of sand. A 

 clay loam is twenty-five to forty per cent of sand and the 

 sandy loam is from sixty to seventy-five per cent of sand, 

 while the light sandy contains from seventy-five to 

 ninety per cent. 



It has been demonstrated by practical experiments 

 that one hundred pounds of sand will absorb twenty-five 

 pounds of water ; one hundred pounds of loam forty 

 pounds ; one hundred pounds of clay loam fifty pounds; 

 one hundred pounds of clay seventy pounds. This ex- 

 plains why some soils always appear drier than others, 



