422 IRRIGATION FARMING. 



porous, it may be possible to give the crop all the 

 moisture needed without surface application. 



If a field has a steep side-hill slope, it is best to bring 

 the water upon it by a supply ditch on the highest 

 part, as shown at a in Fig. 107, and conduct it by a 

 series of dams or drops, b b b, to the lowest part of the 

 field. Then run laterals, c c, from above each drop 

 nearly along a contour or equal level-line on the field, 

 diking these laterals up to keep the water above acci- 

 dental high places. These laterals should be perma- 

 nent and should be near together at the top of the 

 field, the intervals widening as they near the lower 

 edge, as the seepage from the upper laterals will neces- 

 sarily make the ground more and more moist toward 

 the lower edge of the field. The field should be made 

 as long as possible, and the laterals should be made as 

 near parallel as the ground will permit, so as to obtain 

 as large and regular an area between the furrows as 

 possible. Whenever it is necessary to flood growing 

 crops, an opening can be made^ in these permanent 

 ditches at points where the grade-line intersedts a slight 

 knoll. From these openings the water should be con- 

 dudled in zigzag courses, in furrows prepared at the 

 time of seeding, thus preventing washing, and keeping 

 the water as much as possible away from the crowns 

 of plants until it soaks into the soil. A headgate, 

 d d, should be placed at the source of each of these field 

 laterals, and then it is possible for the farmer to so 

 regulate the supply in each part of the field that a suffi- 

 cient quantity may be obtained at the roots of every 

 plant, with very little or no water going to waste at the 

 ends of the field laterals. 



