METHODS OF FURROW IRRIGATION 175 



for the water to sink and spread below the hardpan. It is usual to run 

 this plow once through the center of the interspace between the rows of 

 trees, sometimes at right angles to the irrigation furrows. When this 

 is done the water is admitted to the furrows as usual, but instead of 

 flowing along smoothly it drops into the track of the subsoiler and runs 

 there a long time before rising again to continue its course down the 

 furrow. It is the experience of some growers that the water has taken 

 five or six days to reach the lower end of the furrows, a distance which 

 would have been covered in twenty-four hours if the subsoiler had not 

 intervened. This has been shown to result in much water for the sub- 

 soil and a notable invigoration of trees which had been famishing, 

 although shallow-furrow irrigation had proceeded regularly. 



Recent changes in the furrow method at Riverside, California, are 

 described by Mr. J. H. Reed as follows : 



The handling of the water in the orchard has materially changed in recent 

 years. Instead of flooding up, basining, or using shallow furrows, deep furrows, 

 from 3 to 5 feet apart, are most generally used. In heavy adobe soils more 

 furrows are used than in the more porous granite soils. The most usual length 

 of furrows is 40 rods. Every precaution is taken to have. the surface wetted as 

 little as possible. 



The amount of water run at a time is materially lessened. Formerly the com- 

 mon practice was to run 3 inches per acre for twenty-four hours each thirty 

 days. Now, 2 inches continuous run for seventy-two hours is found to serve a 

 much better purpose, except on loose soils. The general practice in the valley is 

 to irrigate once each thirty days. A few of the most careful orchardists had 

 found that by intelligent and thorough manipulation of the soil they obtained as 

 favorable results from the application of water every sixty days or more, using 

 the same amount as they formerly did at intervals of half that time. The writer 

 has watched with much interest an eight-year-old orchard that during the three 

 years preceding the present received in all but ten irrigations, the usual amount 

 of water being used only at each four irrigations the first year and three irriga- 

 tions each the second and third years, with results comparing favorably with 

 those on trees of the same age on the same soil in neighboring orchards that 

 received the ordinary thirty-day irrigations. While there are few orchardists 

 who .have the skill and patience required to secure such results, they show the 

 possibilities of improved cultivation in conserving moisture. So long as water is 

 abundant and not expensive, more frequent irrigations will probably be generally 

 practiced ; but the advantage of running the water for a longer time, in furrows 

 as deep as possible, covering the saturated bottoms as soon as practicable and 

 keeping the surface perfectly pulverized and in loose condition, is being generally 

 recognized. 



The usual practice is now to have six deep furrows in 20-foot 

 spaces. The number varies according to the character of the soil, but 

 is in any case less than in the small, shallow furrow system which 

 formerly prevailed. 



The recourse to deeper furrows and to the subsoil plowing has 

 been made in several citrus fruit districts of Southern California. Its 

 success depends upon conditions. There are cases in which too deep 

 use of the subsoiler has admitted the water at a point too low for best 

 results to the tree which grows on a leachy subsoil, and the cutting of 

 roots by the subsoiler has in some cases brought shallow-rooting trees 

 into temporary distress. The general conclusion, however, is that 

 deeper introduction of water favors deeper rooting and is very econom- 

 ical of water by preventing the loss by evaporation from the surface, 



