SUB-IRRIGATION AND SUBSOILING. 283 



The difference between wau-r applied to the surface 

 by irrigation and that applied below the surface eighteen 

 inches to two feet, is that in the former case there is much 

 evaporation after the water is applied, and the air has not 

 free access to the soil and roots of the plants for a day or 

 two. In the latter the subsoil is saturated thoroughly, 

 the plant is never deprived of air and the surface soil is 

 kept loose and fine, and there is comparatively small 

 waste, as the water rises slowly when the cultivated soil is 

 reached ; the temperature of the soil is thus more uniform, 

 and the growth of the plant is not varied by changes in 

 supply of moisture, air, and temperature. It has been 

 found by experiment that sub-irrigated soil is warmer 

 than that which has been surface-irrigated, and that the 

 atmosphere around plants to the hight of twelve inches 

 is warmer by sub-irrigation than by surface irrigation. 

 Instead of dilating at length upon the pro and con ad- 

 vantages of sub-irrigation, the writer prefers to give a 

 description of the various methods of applying water in 

 this way, and allow the reader to form his own con- 

 clusions as to the utility of the system considered as 

 a whole. 



Subbing. This is the most natural method of sub- 

 irrigation and it is practiced without resorting to pipes 

 or artificial water ways. It is simply seepage and is pos- 

 sible only on sloping land having a clay subsoil within a 

 foot or two of the surface, and is quite commonly seen in 

 the San Luis valley of Colorado. Wherever irrigation 

 is necessary for the production of a crop, it will be 

 found of great advantage at the time of seeding to make 

 ditches and furrows at short intervals, and then to so 

 check the water in these ditches that it may stand in 

 small bodies at a level above the general surface of the 

 ground to be irrigated. If the water is held constantly 

 in these small reservoirs during the growing season, it 

 will not be necessary to flood the ground so often ; and 



