METHODS OF IRRIGATION 167 



Summer Irrigation. When this shall begin and when end are to 

 be locally determined. In some places even the earliest fruits can 

 not reach satisfactory size and quality without irrigation. In others 

 rainfall with winter irrigation will suffice for proper development of 

 early fruits, but not for late. In both cases the fruit may be satis- 

 factory, but the tree unable to hold its leaf vigor until the work of 

 the growing season is properly completed. It is then apparent that 

 local practice must vary in order to reach the universal fact, and 

 that is that all through the active season the tree must have constant 

 and adequate moisture supply. Many evils in lack of bearing, in 

 dying back, in unseasonable activity and the like are due to in- 

 adequate, intermittent and, in some cases, to excessive moisture in 

 the soil. 



Cultivation and Irrigation. Although the relations of irrigation 

 and cultivation have been freely discussed, it must be remarked in 

 this connection that with such an extension of irrigation practice as 

 is now realized, there is danger that those who have previously 

 trusted so fully upon good cultivation may swing to the other ex- 

 treme and trust too much to the stream of water and too little to the 

 plow and cultivator. There is a temptation this way when one finds 

 that he can run water in large amounts very cheaply. Not only is 

 there danger of over-irrigation in the growth of tree and fruit, but 

 the ill effects of water upon the soil, when unattended by good culti- 

 vation, are constantly threatened. The tree needs air as well as 

 water ; it needs a certain free condition of the soil for its best root 

 action. These needs can be amply secured when adequate applica- 

 tion of water is quickly followed by soil-stirring. Irrigated soil when 

 amply supplied with organic matter, is delightfully mellow and free 

 and of condition to invite the fullest activity on the part of the tree. 

 Irrigated ground not properly treated becomes compacted, fissured, 

 cloddy and generally hateful, losing moisture rapidly, setting around 

 the roots like cement and tearing them by its subsequent shrinkage. 

 These conditions do not occur on the lighter soils, and yet even these 

 are best when cultivated in a rational manner. 



METHODS OF IRRIGATION 



There are various methods employed in California for the con- 

 veyance and application of water to trees and vines. Some of the 

 principal ones will be described. 



As this writing does not pretend to be a treatise on irrigation 

 engineering, no attempt will be made to secribe the more ambitious 

 undertakings, which should never be entered upon without the en- 

 gagement of a qualified engineer. Nor is it possible to discuss the 

 numerous devices which are covered by patents. Investment should 

 always be preceded by visits to irrigation works now in operation, 

 and procedure should be guided by observation. The hints presented 

 herewith relate chiefly to things the irrigator can do for himself. 



Free Flooding. Flooding that is, the free flow of water over 

 the whole surface, or the flow between rows with furrows near the 



