Development of Pistachios with Saline Irrigation Water and Regional Salt Tolerance in Pistachio Production Fields

The published and currently accepted root zone salinity threshold for California pistachios of 9.4 dS/m ECe with an 8.4% relative yield decline above that level was developed from a small plot study for 8^th through 13^th leaf yields in northwestern Kern County from 1997-2002.  A second large scale study applied fresh and saline irrigation treatments (0.5 to 5.2 dS/m EC) from planting through 10^th leaf yields.  Average 2011-14 root zone salinity ranged from 2.5 to 13.2 dS/m and caused a significant edible in shell yield reduction of 108 to 264 kg/ha (~3/1% decline) depending on rootstock in the combined 4 year yield for every unit EC (dS/m) increase over 5 to 6 ds/m.  A greatly expanded salinity survey including 9 commercial fields (9^th – 13^th leaf) in western Kern County with more than 130 individual tree data points ranging from an average root zone salinity of 1.4 to 22.3 dS/m resulted in a similar yield reduction of 48 kg/ha edible in shell for one season for every unit EC above 5 to 6 dS/m.