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<br />(~ classes was obtained from Bowman (1973) the Soi 1 Series permeabi lities and the <br />.:. Agricultural Commissioner's acreage report, Little (1968-73). The very rapid, <br />t.:::I and rapid pel'meabilltles were placed in the group labeled Rapid. The moderately <br />~ rapid and moderate were labeled moderate, and the moderately slow, slow, and very <br />s.ow were labeled slow. <br />Table 48 presents the effective saturation extract values. The surface i rri- <br />gation salinity was taken from the 35 irrigation per year line of table 8. The <br />rationalie being that 10 to 15 inches of rain would have a diluting effect simi lar <br />tq additional irrigations. The sprinkler values were the same as previously used. <br />The ne~1 tl"ickler or drip method of irrigation seeing rapid expans ion in this areil, <br />Valley Center HHD (1973) appears to deliver water to root systems at the same con- <br />centration as the Irrigation water. The effective salinity was reduced one mmho/cm <br />below the Irrigation water value because the CaS04 would have no harmful effect <br />and rainfall would provide dilution and leaching, Hall (1971). The first trials <br />o! trickier systems support this useage, Hall (1971), Hall (1973), Valley Center <br />MHD (1973). <br /> <br />The use of drip Irrigation has produced advantages in water saving, labor <br />saving, convenience In harvesting, and reduced weed control. The drip method Is <br />b~ing adopted for these reasons and would proceed even though the water contained <br />no salt. For this reason, it would not be appropriate to charge the $200-$300/acre/ <br />crop, Hall (1973), to increasing salinity, particularly in the rapid and moderately <br />drained soils. In the slowly drained soils a yield benefit is projected because <br />of. salinity reduction. Therefore, a portion of the cost of drip irrigation should <br />be charged to the Increasing salinity. <br />Avo~ddo is seeing extensive development with drip irrigation, Valley Center <br />MHD (1973). The requirement of rapid permeability soils for this crop places It <br />In areas where salinity will probably not be a problem even at 1,400 ppm. The <br />citrus and tomato plantings on rapid and moderately permeability soil show little <br />yield reduction, but the slow permeability soil show drastic reductions In yield. <br />The drip or trickIer irrigation would see great advantages here. It should be <br />noted that a sprinkler system may be required to periodically leach out salt <br />accumulations between plants, Hall (1971). It should also be noted that this <br />analysis ~sumes that the mean annual rainfall will continue. In drought years <br />t~~ number of sprinkler leachings may need to be Increased. <br />It Is of interest that long term citrus plantings Irrigated with Colorado <br />River water (740 ppm) on a moderately slow permeability soil showed a l~!o reduction <br />In yield, Gln9nam, et al. 1973). Table 22 shows an 18% yield reduction at 900 ppm <br />which is in general agreement. <br /> <br />47 <br />