The Data: Soil-Water Analysis
After three seasons of irrigation this program results in about 6,600 lb/ac applied salt in the Aqueduct treatment and about 54,000 lb/ac in the Well treatment. The salt load in the 9 foot band along the pistachio drip tape after 3 years was about 4,000 and 40,000 lb/ac for the Aqueduct and Well treatments, respectively (Table 1). In Table 1, note that EC+ is the maximum increase in soil samples (prepared for analysis as saturated paste) over initial soil salinity with no precipitation of salts and no leaching past the 5 ft depth. This value assumes 640 ppm of soluble salt = 1 dS/m and 5 acre-ft depth of soil = 20 million lbs.
Table 2 provides an analysis of irrigation water for the three treatments at the end of the third year (2007).
Total salt loads applied to pistachios would only be half of this if cotton had not been interplanted for the first two years as the cotton pulled substantial amounts of water from the pistachios. Net leaching from the pistachio root zone was estimated at 5-20%.