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Wednesday, 27 May 2009

The most widely used nut crop in the world benefits from potassium with increased yields and quality.

Origin, requirements and production
The almond (Amygdalus communis, Prunus amygdalus, or Prunus dulcis) The almond (Amygdalus communis, Prunus amygdalus, or Prunus dulcis) is a member of the Rosaceae family, and closely related to the peach, plum, apricot, and other stone fruits. The cultivated almond originated in the deserts and lower mountain slopes of Central and Southwest Asia. From India and Persia it spread into the Mediterranean to Italy, Spain, and Northern Africa. Almonds are mentioned throughout history. By around 4000BC humans learned to cultivate the tree, and almonds were in use in nearly every ancient civilization. Historians generally agree that almonds and dates, both mentioned in the Old Testament of the Bible, were among the earliest cultivated foods. Throughout history, almonds have maintained religious, ethnic and social significance. The Romans showered newlyweds with almonds as a fertility charm. The earliest varieties of almonds were found in China carried by traders down the ancient silk road to Greece, Turkey, and the Middle East. The English word almond is derived from the French amande, which in turn is a derivative of the old Latin word for almond, amygdalus, literally meaning "tonsil plum." The almond tree was brought to California from Spain in the mid-1700's by the Franciscan Padres. It wasn't until the following century that trees were successfully planted inland. By the 1870's, research and cross-breeding had developed several of today's prominent almond varieties.
Almond plants grow from seed in wild and semi wild areas. Throughout the years, growers have selected varieties that offered outstanding qualities, and were well suited to local conditions. This varieties, were propagated by budding or grafting into seedling rootstocks. The same process occurred in California were variety selection started quite early after introduction, since the European varieties were not satisfactory for California conditions.
The growing requirements for almonds are quite demanding, and thus distribution of commercial production is limited to specific areas in the world. Almonds grow best in areas with cool and wet winters, followed by a mild spring, a warm and dry summer and a mild fall. The tree is relatively cold hardy, and cold hardiness is not a major limiting factor. The tree requires chilling temperatures during winter dormancy for normal spring growth and flowering. The required chilling hours are 300 to 500 hours below 45F or 7.3C. In regions with cold winters the tree may bloom after relatively short periods of warm temperatures in late winter. Thus, blooms or small fruits are susceptible to frost. Rain and high humidity during the growing season have adverse effects. During bloom time rain and cold weather can reduce bee activity and cross pollination and therefore the size of the crop. Also, rain and high humidity favor fungal and bacterial diseases. Although the almond tree is hardy to drought, commercial production is best in regions with a long dry summer and with proper irrigation, fertilization, and intensive management.

According to FAO statistics the top almond producers in the world in 2003 were the United States, Spain, Morocco, Iran, Italy, Greece and Syria. Following are tables, and figures illustrating hectares under production, yield, and production in the major producing countries. 

Major Almond Producers in the World

Almonds 2002
Area Harv (ha)
Area Harv (ha)  Yield (hg/ha)  Production (Mt)
Greece 39,950 
Iran, Islamic Rep of
Italy 86,040 
Morocco 134,141 
Spain 664,000 
Almond Production 2003
CY 2002 Leading Exporters Shelled Almonds
Source: USDA, FAS “Almond Situation and Outlook, April 2004, p.4.
CY 2002 Leading Exporters of In-Shell Almonds
Source: USDA, FAS “Almond Situation and Outlook, April 2004, p.4.
Crop Year
Australia California Chile Greece Italy Spain Turkey Total CA % of Total
2004-05 25.3 998 16.5 37.5 26.5 57,7
 21.1 1,188,60
2005-06 35.7 911.7 9.3 30.9 26.5 140 33.1
 1,187.20  77%
2006-07 31.5
1,116.70 14.6 33.1
13.2 182  31.7 1,426.40
2007-08 58.5 1,383.00 14.6 30.9
26.5 149.9 34.2
Sources: Almond Board of California, Almond Board of Australia, USDA, Foreign Agricultural Service.
Note: Reported countries account for nearly 100% of world production
California’s Share of World Production


Almonds and nutrition

Almonds are the most widely-used nut for confectionery items like candy bars, cakes, toppings, etc. Much of the crop is roasted and flavored or salted and sold in cans; broken and small kernels go to confectionery. US consumption of almonds is 1.3 lbs/year, doubling over the last 25 years.

Almonds are an excellent source of vitamin E and magnesium, a good source of protein and fiber, and offers potassium, calcium, phosphorous, iron, and heart-healthy monounsaturated fat. 

Almonds Dietary Value, per 100 gram Edible Portions, Unroasted

Nutrient Units Value per 100 grams
Water g 4.70
Energy kcal 575
Energy kJ 2408
Protein g 21.22
Total lipid (fat) g 49.42
Carbohydrate, by difference g 21.67
Fiber, total dietary g 12.2
Sugars, total g 3.89
Vitamin C, total ascorbic acid mg 0.0
Thiamin mg 0.211
Riboflavin mg 1.014
Niacin mg 3.385
Pantothenic acid mg 0.469
Vitamin B-6 mg 0.143
Folate, total mcg 50
Choline, total mg 52.1
Betaine mg 0.5
Carotene, beta mcg 1
Vitamin E (alpha-tocopherol) mg 26.22
Fatty acids, total saturated g 3.731
Fatty acids, total monounsaturated g 30.889
Fatty acids, total polyunsaturated g 12.070
Cholesterol mg 0
USDA National Nutrient Database for Standard Reference, Release 21 (2008)


Many clinical studies over the past 10-15 years have shown the health benefits of almonds in lowering cholesterol and LDL. For additional information on health benefits of almonds you can access: http://www.almondsarein.com/


Potassium: for enhanced yields and productivity

Almonds, as other fruit and nut crops, remove a substantial amount of N, P, and K per year in the harvested fruit. A balanced fertilization program that replenishes nutrient removal is essential for efficient nutrient use and for maintaining high productivity.

Nutrients removed by harvested crop (in shell) in almonds
  Lbs / ton kg / mt
N 130 65
P2O5 50 25
K2O 110 55

Total fruit K removed in 1999 per 1,000 lb of Nonpareil almond kernels (meats)¹

  Low K High K
Fraction Weight lb² K conc. % K removed lb K O K conc. % K removed lb K O
Kernel 1,000 0.7 8.4 0.7 8.4
Shell 400 1.5 7.2 2
Hull 1,200 1.7 24
2.6 37.2
Total     39.6   55.2
¹ Includes the mesocarp plus exocarp
² Kernel / shell / hull ratio data (not presented) indicated no yield differences among treatments in 1999

Better Crops/Vol. 85(2001,No. 3)

University of California research indicates that inadequate potassium availability is a limiting factor in almond production in California. Differential potassium sulfate applications showed a statistically significant yield response to potassium fertilization. Nut yield was increased by 400 meat lb/A. Leaf sampling in July is a good predictor for next season’s productivity, but not for the current season. Also, a leaf concentration of 1.4% K in July seems to be an adequate predictor of crop yield in the following year , in spite of the substantial increase in yields since the establishment of this guidelines in the 1960s. No yield response for potassium was found at fertilization rates exceeding 240 kg ha-1 of K. 

Treatment Leaf (K) (% dry wt.)* Nut Yield (kg ha-1)
 (kg K ha-1) 1998 1999 2000 1998 1999 2000
0 1.1 0.7 0.7 870 4400 2700
240 1.3 1.3 1.2 1000 4300 3200
600 1.3 1.6 1.4 930 4900 3200
960 1.3 1.7 1.7 1200 4500 3100
P linear <0.01 <0.01 <0.01 0.08 0.14 0.04
P quatratior <0.01 <0.01 <0.01 0.07 0.09 0.06
*K fertilizer treatment began in 1998
*Potassium sulphate, expressed as elemental K
*Samples takung during the last week of July

Journal of Horticultural Science & Biotechnology(2004)79(6)906-910

Almond yield is determined by fruit size and fruit number. There is evidence from other fruit crops that potassium as an effect on fruit size. Fruit number in almonds though is a much more important yield determinant. In almonds, flower buds develop laterally on short spurs and have 1 to 5 or more flower buds. The terminal bud is always vegetative and maintains the elongation of the spur from year to year. Almond bud differentiation occurs during the summer prior to flowering, and the external appearance of leaf and flower buds is similar. Normal flower bud development in the fall and winter requires adequate moisture and a number of chilling hours to overcome dormancy.


University of California research shows that a potassium deficiency in almonds is likely to be cumulative, and very pronounced after heavy cropping years. Also, a K deficiency will impact almonds yields negatively in subsequent years by increasing the mortality of fruit bearing spurs and reducing flowering of potassium deficient spurs. Return bloom was lower on low-K fertilized trees versus high-K fertilized trees. This might have been caused by spur mortality, decreased initiation of new spurs, and/or reduced number of flowers per spur. For this reason it is imperative to replenish and recharge the potassium “soil bank” on a yearly basis. By following a maintenance program, almond growers will avoid the onset of a K deficiency and ultimately yield reductions. 

Effect of Tree K Status on Yield Determinants Measured on Individual Branches, Beginning Eight Months After Differential K Fertilization Was Initiated¹

lb K2O/ A
**** Fruit set, % **** Nodes /shoot **** Weight, 1999, g **** Return bloom, %
  1999 2000 1999 Embryo Whole fruit
0 2.7 ± 2.4 2.1 ± 2.2 11.1 ± 0.86 0.95 ± 0.04 2.76 ± 0.05 2.3 ± 3.2
960 2.6 ± 1.8 2.5 ± 2.2 11.6 ± 0.43 1.01 ± 0.01 2.75 ± 0.09 3.3 ± 4.6*
* means ± Standard Error (SE)
* Denotes means which differ at p < 0.10

Return bloom: flower number in 2000 divided by flower number in 1999
Better Crops / Vol. 85 (2001, No. 3)

The data shows that there was a 27 percent increase in mortality of spurs that fruited in 1999. This accounts as a major factor in the lower return bloom and reduced yields of low K trees in 2000. Tree K status did not influence the mortality of non fruiting spurs in 1999. Thus, the effect of K deficiency was localized to fruiting spurs. 

Effect of Tree K Status on Subsequent Productivity of Spurs Tagged in 1999

    *** Spur status in 2000, % of total sample ***
lb K2O / A
N= Vegetative Fruiting Dead
0 Fruiting 133 26 18 56
960 Fruiting 172 31 27 42
0 Vegetative 113 21 77 2
960 Vegetative 138 16 77 7 *
* Denotes means which are significantly different at p < 0.05

Better Crops / Vol. 85 (2001,No. 3)

The symptoms of potassium deficiency in almond trees show up in early to mid summer, in the upper part of the canopy, as pale leaves (similar to nitrogen deficiency), curling and rolling of the leaf blade, chlorotic and then necrotic leaf margins. The first leaves to be affected are generally along the middle of the shoots. The tips and margins of the leaves become necrotic, and this causes the leaf tip to curl upwards. This upward rolling of the leaf is called “Viking’s prow”. Leaf size and shoot growth are decreased as well by potassium deficiency. On fruiting spurs, leaf chlorosis and premature leaf fall occur in the lower portion of the tree canopy.

K Deficiency in Almonds
K Deficiency in Almonds
Courtesy of Dr. Patrick Brown, University of California, Davis


Fall is an ideal time to supply perennial crops with the nutrients needed for growth the following season. Fall applied potassium will be taken up by almond trees as long as the roots are active. Potassium will then be translocated to the top where it will be stored until needed. Fall applied K will also get incorporated into the soil by fall and winter rains, recharging K depleted soil sites. In this way, K is readily available to be taken up by the active root system the following spring. This is the most critical period for potassium availability in almonds due to the rapid vegetative growth, and fruit development after flowering. Thus, making sure that potassium is readily available when the plant needs it most, is a good management practice that will avoid temporary nutrient deficiencies. Temporary deficiencies compromise production at the critical period of early fruit and leaf development.


The benefits of SOP in almonds
  • Encourages better fruit wood development and flowering.
  • Contributes to the overall health of the tree
  • Helps trees grow consistent bud sets and crops
  • Increases the size and quality of nuts
  • Promotes uniform root growth
  • Improves water use through regulation of photosynthesis and transpiration
  • Low salt index minimizes crop damage caused by soil salt build-up
  • Low chloride content minimizes potential chloride damage and subsequent yield reductions
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