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Pistachio Nutrients & Fertilization

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 exisiting 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 fertilzation 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.

 
 

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

 

 
 

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.

 

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)

1.14%

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.

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, Mendicino 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 chleated 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

a great link for more information:  Robert Beede's Kings Co. website