Robert H. Beede, UCCE Farm Advisor, Kings Co.
A fertilization program is typically designed for a specific crop and orchard. At establishment, the soil is sampled for existing available nutrients. After the application program is initiated, leaf analysis in mid-August is used to monitor it. Growers are advised to keep long-term records for an orchard of: their application program, including applications of fertilizer and soil amendments, results of leaf sampling, and yield. These records provide information for decision-making in orchard management.
Application Program: Nutrients are best applied to the root zone at the time of greatest need, which is typically early in the season. Due to the "alternate year" nature of the pistachio yield, fertilization is lighter during "off" years. General fertilization schedules for nitrogen (N) and potassium (K) below should be modified for extremes in soil type: on very heavy clay soils, K applications would be very light. Interactive models have been developed to customize an N and K fertilization program to a specific site. The schedules below provide a generic fertilization schedule, applicable to most pistachio growing areas in California.
Table 1. Fertilization Schedule for Pistachio - "On" Year (lbs/acre) (Roland Meyer, 2008)
|Nutrient||April||June||early August||"On" Year Total|
|N||30 - 75||50 - 75||50 - 75||ca. 200 - 225|
|K||35 - 75||35 - 75||35 - 50||ca. 110 - 200|
Table 2. Fertilization Schedule for Pistachio - "Off" Year (lbs/acre) (Roland Meyer, 2008)
|Nutrient||April||June||early August||"Off" Year Total|
|N||30 - 60||35 - 50||35 - 50||ca. 100 - 113|
|K||12 - 35||12 - 35||12 - 25||ca. 36 - 100|
Leaf Sampling for nutrients: This is an extremely tool to measure the adequacy of the fertilization program and to diagnose nutrient deficiencies and toxicities. Annual leaf sampling is advised.Samples are analyzed at commercial labs. To provide an acceptable sample:
- collect the sample from late July through mid-August
- sample non-fruiting branches, 6 ft. (1.8 m) from the ground
- choose fully expanded sub-terminal leaflets
- collect 4 - 10 leaflets per tree
- sample 10 - 20 trees/orchard block
- do not include leaflets that have received in-season nutrients sprays
- deliver the sample to the lab within 24 hours
Critical Values (CV) are minimum concentrations for adequate tree growth and yield. Suggested Range also refers to the concentration for optimal growth. These values are part of the leaf analysis report. CV and Suggested Range values for essential nutrients are provided in the table below.
Table 3. Nutrient Concentrations in August Leaf Samples
(R. H. Beede, 2004)
|Nutrient||Critical Value (CV)||Suggested Range|
|Nitrogen (N)||1.8%||2.2 - 2.5%|
|Phosphorus (P)||0.14%||0.14 - 0.17%|
|Potassium (K)||1.6%||1.8 - 2.0%|
|Calcium (Ca)||1.3% (?)||1.3 - 4.0%|
|Magnesium (Mg)||0.6% (?)||0.6 - 1.2%|
|Chlorine (Cl)||(?)||0.1 - 0.3%|
|Manganese (Mn)||30 ppm||20 - 80 ppm|
|Boron (B)||90 ppm||150 - 250 ppm|
|Zinc (Zn)||7 ppm||10 - 15 ppm|
|Copper (Cu)||4 ppm||6 - 10 ppm|
Nutrition Deficiencies: Generally, sandy soils are more prone to deficiencies because, due to the crystalline structure, they have fewer binding surfaces than clay soils.
Table 4. Symptoms and susceptibilities of nutrition deficiencies in both pistachios and alomnds.
|Nutrient||Seasonal Onset of Symptoms||Regional Susceptibilities & Conditions||Shoot & Foliage Symptoms||Corrections*|
|Nitrogen (N)||throughout season||all regions benefit from annual applications||shoot reduction, new leaves pale, old leaves yellow & drop, leaf midribs & bark reddish||Table 1|
|Potassium (K)||early to mid-season||high native K fertility observed in West side, due to heavier soils||leaves pale, small, leaflet edges curl up with gray cast, leaf yellowing, scorching; decreased yield||Table 1|
|Magnesium (Mg)||mid-season||alkaline, calcareous, boric soils & heavy gypsum applications may induce deficiency, due to Mg uptake by cations||confirm by leaf analysis, as visual leaf symptoms of Mg deficiency are very rare||requires site-specific evaluation|
|Boron (B)||early season||severe deficiency in some areas of Lake, Mendocino counties||yellow, misshapen leaves, terminal dieback; trees appear stunted||Borax in Sept; foliar soluble B at bud swell or post-bloom|
|Zinc (Zn)||early season, in young bearing trees||all regions, particularly soils with history of animal manure application||delayed bud opening, terminal leaves small & yellow, wavy leaf margins, terminal dieback, reduced nuts & more blanks.||Zn sulfate in late postharvest, or bud-swell|
|Copper (Cu)||mid to late season, in young bearing trees||alkaline soils susceptible||terminal leaf tip and margin burn, leaf scorching & drop, terminal dieback.||foliar chelated Cu in post-bloom period|
*Note: bud-swell is typically late Feb. - early March; Post-bloom is typically late April - early May; Postharvest is typically late Oct. - early Nov.
Chemical Toxicities: An excess of the elements below in irrigation water or soil may cause toxicity. If water is the problem, the source would have to be changed; if moderate levels exist in irrigation water, add a 'leaching fraction' to the amount of applied water. Elements can be leached from soil by irrigation water by addition of a 'leaching fraction'. the 'leaching fraction is a calculated amount
- B toxicity: mid to late season, brown leaf tips and margins and between veins, twisting of leaves; gumosis, oozing of sap for the trunk, may also occur.
- Cl and Na toxicity: brown leaf tips and margins
2012 PISTACHIO DAY PRESENTATION (PDF of PowerPoint)
What's the Latest in Pistachio Plant Nutrition?
Patrick Brown, UCCE Specialist and Professor of Plant Nutrition, UC Davis
Source: Pistachio Production Manual, 5th Edition (2008)