266 ENGINEERING ON THE FARM 



of applying the water also varies with the nature of the 

 crop, the soil, and climatic conditions. Irrigation Investi- 

 gations, Bureau of Public Roads, United States Department 

 of Agriculture, Washington, D. C, has prepared numer- 

 ous bulletins relating to individual crops and the proper 

 methods of irrigation, as well as to the various appliances 

 and methods of applying the water. These publications 

 may be had on request, and persons interested in any 

 special crop or locality are advised to write to that office for 

 information. 



Comparison of methods. Any system of irrigation that 

 is permanent and will do thorough work is expensive. When 

 the subirrigation or the spray system is used, expensive 

 equipment is necessary. When the surface methods are 

 used, much time and labor are required to place the surface 

 of the land in suitable condition. In pioneer days, when 

 land was plentiful, no attempt was made to irrigate any but 

 tracts of land that were naturally favorably situated. 

 Rough and uneven lands were neglected. The demand 

 for increased farm lands and the scarcity of water due 

 to more water users have made it necessary to improve 

 unfavorable lands and to place them in such condition 

 that the water available will extend over a maximum area. 

 The arrangement of the farm and the laying out of fields 

 should be done after the location of the water-supply 

 ditches has been determined. The system of farm manage- 

 ment and cultivation must adjust itself to the water supply 

 to prevent evaporation and to secure the greatest benefit 

 to the plants. After irrigation the land should be culti- 

 vated as soon as the water is turned off, unless the sub- 

 irrigation method is used. The method of applying the 

 water should be one that will adapt itself to local condi- 

 tions and will distribute the water uniformly throughout 

 the soil layers so that it will reach the area occupied by 

 the plant roots and be available to the plant. Economy 

 of both labor and water should be considered, as in the 



