IRRIGATION AND DRY-FARMING 



705 



sometimes the case in strawberries, in order to permit 

 harvesting. 



In orchard culture two or more furrows are placed 

 between each two rows. Often for young trees a furrow 

 is placed on either side at a distance of about two feet, 

 this distance being increased as the trees increase in size. 

 The furrows are temporary and are usually renewed 

 after each application of water, as the establishment of a 

 soil mulch is necessary in order to prevent excessive loss 

 of water by evaporation. 



604. Size and form of furrows. In shape the fur- 

 rows should be relatively narrow and deep. Water is 

 conserved by this form in three ways : (1) it flows more 

 freely, both in the furrow and into the soil ; (2) less surface 

 is exposed to evaporation ; and (3) the surface mulch is 

 more easily maintained. (See Fig. 80.) Under arid con- 

 ditions a deep mulch l of six to eight inches is most 



3 FT z 



FIG. 80. Diagram showing the relative advance of water into the soil 

 from a deep (left) and a shallow (right) irrigation furrow. Note 

 the relative extent of surface soil wet in the two cases. A deep 

 mulch and deep irrigation furrows aid ia the conservation of 

 moisture. 



1 For tier, S. Evaporation Losses in Irrigation and Water 

 Requirements of Crops. U. S. D. A., Office Exp. Sta., Bui. No, 

 177. 1907. 

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