SOILS AND FERTILIZERS 



93 



stirred soon after the water is applied. A great dis- 

 advantage in this method is the great length of time 

 necessary to apply water in sufficient amount. This is 

 necessarily so because of the fact that the air in the soil 

 prevents, after a little, the rapid penetration of the 

 water, as the increasing weight of the water above pre- 

 vents the escape of the air in that direction. 



Furrowing. This method is the one most commonly 

 used in the western part of the United States. Small 

 furrows are dug through the land, the depth and dis- 



FIG. 34. Irrigation by Furrows. 



tance apart varying with the soil. The more porous 

 soils require a greater number of furrows than clay or 

 silt. The furrows must slant a little, but not enough to 

 make a rapid flow of water or there will be washing. 



One of the chief advantages of this method lies in the 

 fact that the water can soak into the soil so that the 

 lower strata become so thoroughly saturated that a deep 



