134 DRAINAGE AND IRRIGATION 



directly into irrigation ditches. It may be forced by the pump 

 directly through pipes to the fields. 



Methods of Applying Water. Water may be applied to fields 

 where crops and orchards are growing in several different ways. 

 One of the most common methods is to conduct the water along 

 shallow ditches and let it flow from them into furrows which run 

 along the rows of the growing crop. In the fields of clover, al- 

 falfa or other sowed crops the furrow system is also sometimes 

 used (Fig. 90), but has the objection of leaving bare strips where 

 the crop has been killed by the furrow. For such sowed crops 

 the method known as flooding is more commonly used. The field 

 when laid out may be levelled if necessary, so that water flowing 

 in at one side will spread somewhat evenly through the surface 

 without washing the soil or damaging the growing crop. 



Fia. 90. Irrigation of wheat as seen here is practiced only where the water rights are low. 

 The method here in use is known as the "open furrow method." (U. S. D. A.) 



Subirrigation is sometimes practiced by laying tile deep enough 

 in the ground to avoid damage when plowing. Irrigation water is 

 allowed to flow into the main, which is slightly higher than the 

 laterals, and water is thus conducted to the whole garden or field. 

 This system is applicable only to small areas-. It has the advantage 

 of not wetting the surface and thus puddling the soil or causing it 

 to bake. Such difficulties are sometimes found in other systems 

 of irrigation. 



Overhead pipes, placed on posts high enough to allow the work 

 of men and teams under them, are used to supply water directly 

 to truck crops. Each line of pipe running across the field is con- 

 nected with the head pipe, supplying water to all the lines. The 



