130 



LAND DRAINAGE AND IRRIGATION 



3. Spray Irrigation. Spray irrigation is the process of applying 

 water to the surface of soils or to crops in the form of small drops, 

 spray or mist. The first systems of spray irrigation were the out- 

 growth of city lawn and garden sprinkling. It was soon found that 

 through such spraying, small amounts of water could be applied 

 advantageously to delicate crops, especially for supplementing 

 an uncertain rainfall. 



The water used is conveyed to the field under pressure through 

 pipes or hose. This system of irrigation is well adapted to those 

 conditions in humid sections which demand small and frequent 



Fia. 65. The Skinner system of irrigation. A field piped for overhead spray irrigation. 



(U. S. D. A.) 



applications of water in the preparation of the soil for transplanting, 

 and for supplying quick-growing, market-garden crops and berries 

 with the moisture they so much need for best growth, and especially 

 to keep them thriving during dry periods (Fig. 65). 



4. Sub-irrigation. Underground or subsurface irrigation im- 

 plies that the irrigation water is applied from below the surface. 

 This may be accomplished through the use of open ditches and 

 underground tile, or pipes of iron, concrete, or wood. 



The open ditch method of sub-irrigation has proved successful 

 to a limited extent in western America and in Florida. 



The underground pipe system of irrigation has not met with 

 success, except under exacting soil conditions found in only a 

 few localities. At Sanford, Florida, the same tile used in sub- 

 irrigation also serves for drainage during wet seasons. 



