Pistachio trees are one of the most valuable crops grown in California’s Central Valley. With so much value, it is not hard to find a pistachio orchard while driving up and down Highway 99 or Interstate 5. Despite so many acres being dedicated to pistachio farming, pistachios are actually not native to California, they are native to the Middle East, a far cry from Fresno and Kern Counties. Pistachios first made an appearance in the United States in the 1930’s, with increased development starting after 1960. Now, across many acres of California’s “Westside” you will easily see pistachio orchards ranging from 100 to 2,000 acres, varying in age from 7 months to 17 years.
Currently California is estimated to have over 300,000 acres dedicated to pistachio production. Of those 300,000 acres, just over 232,000 are bearing acres (annual crop that has come into production), which is a 122% increase in a decade. Each bearing acre yields 2,300 to 3,100 pounds of pistachios. Pistachio trees are an alternate bearing crop which means, one year the yield is up and the next year it is down. Alternate bearing begins around the 9th year of production although yield can be obtained as early as the 6th year. In 2015, California pistachio growers faced great challenges not directly related to water, despite the ongoing drought.
Pistachio trees require low temperatures in the winter months in order to develop new buds for the next season. Above average temperatures during the winter of 2014/2015 have been blamed for an average yield per bearing acre of just 1,161 pounds. This was over a 1,000 pound decrease from the 2014 average of 2,329 pounds. In perspective, growers lost an average return of over $3,600 per acre using the 2014 average return per pound of $3.10. 2015 is likely to be better for growers as El Nino is to bring increased storm activity to the Central Valley and should lower the average temperature during the winter months. Aside from the benefit of being one of California’s most valuable crops, pistachios are also intriguing to growers because of their tolerance to salt and deficit irrigation. Pistachios are being planted into areas of land that are lower valued for farming because of high salinity in the soil, making it difficult to grow crops such as tomatoes, almonds and lettuce.
Also, in many areas, increased drought in the state along with an inconsistent supply of irrigation water from the water districts has led to a large increase in new well developments. These new wells are being drilled at a record pace as well as depth. With increased depth comes increased salinity in the water, and in some cases, almond orchards are being “burned” alive because of high salt content in irrigation water. Pistachios are not salt resistant, but are salt “tolerant”, making them a viable crop in these areas. Pistachio trees can also be grown on less water than almonds.
Studies have shown that with drip irrigation and a scheduled deficit irrigation plan, pistachio trees can be kept alive with just over 3 acre feet of water. For commercial production, pistachio trees can be grown with 44 inches of water with drip irrigation compared to almonds that generally require 48 inches on average.
- Spacing – Pistachio orchards are usually planted in either late fall or early to mid-spring after the last rains have happened. Trees are spaced 19-21 feet between rows and 16 to 19 feet between trees in row. The average is around 137 trees per acre
- Irrigation – Almost all pistachios in California are irrigated using micro-irrigation with a vast majority using drip irrigation. Due to drip irrigation and large developments, very little acreage uses or even has flood irrigation capability. Pistachio growers are opting to use drip irrigation instead of micro-sprinkler irrigation because of environmental factors and crop preferences. Pistachios do not like a saturated root zone and do not respond well to high humidity in the orchard, which can cause disease issues. Also, because pistachios are salt tolerant, leaching salts is less of an issue in pistachio farming, so micro-sprinkler irrigation is not necessary. Pistachios can have a daily ET as high as .35 inches in hot and dry climates, .33 inches is an acceptable value in most parts of the Central Valley
A drip irrigation example for pistachios would look similar to this – Pistachios planted in 20 foot rows, with trees spaced 16 feet apart in each row, have one line of blank tubing per row next to the trees. Two gallon per hour ClickTif Button emitters are punched into the blank tubing approximately 24 to 30 inches on each side of the tree. After the second or third year, a second line may be added with two more additional emitters. Two lines, with two, two gallon per hour drippers per tree results in an application rate of .040”/Hr. With an assumed daily ET of .33 inches, an 8.22 hour irrigation set would be required to match ET for the day. This system would require 18.15 GPM/Ac. to operate
Jain Irrigation products most likely to be used
- Supply Tubing—.940x.830, .820x.720, .710x.620; One/two lines per row
- ClickTif Button Emitter-.5GPH, 1GPH, 2GPH; three to six per tree
- Amnon/TopDrip 18/20mm, .42, .53, .61GPH, 24-40”; two lines per row