Almond Production #

 

The almond tree, Prunus dulcis, is a deciduous tree in the family Rosaceae which is grown for its edible seeds (nuts). The tree has brown or grey bark and either an erect or weeping growth habit depending on the variety. The trunk can reach 30 cm (12 in) in diameter. Almond leaves are 7.5–13 cm (3–5 in) long with a serrated edge and grow alternately on the branches. The tree produces white to pale pink flowers and hairy green fruits which are oblong in shape. The fruit is a drupe, containing a single seed. The seed is protected by a hard brown shell. At maturity, the flesh of the fruit becomes leathery and splits to reveal the nut inside. Nuts generally measure 3.5 to 6 cm (1.4–2.4 in) in length. Almond trees can reach heights between 4 and 10 m (13–33 ft) and have a commercial lifespan of between 30 and 40 years. Almond may be referred to by variety and this includes bitter almond nuts are generally about long and may also be referred to as sweet or bitter almond depending on variety and originates from wild species found in Central and Southwest Asia. https://plantvillage.org/topics/almond/infos

 

Site Preparation #

Land is prepared beginning with slip ploughing to break up layered soil for improved root and water penetration. Ripping is performed where chemical hardpans exist. The ground is disced twice after slip ploughing and borders are put up. The bordered orchard site is flooded with eight acre-inches of water and disced two more times after the ground has dried out. Following the second discing, berms are constructed in the tree rows to manage irrigations between the rows. The field is laser levelled to allow for uniform irrigation. Slip ploughing and levelling are performed by contract or custom operators. A treatment of soil-residual herbicide is applied to the tree rows and incorporated with a disc after levelling. All operations that prepare the orchard for planting are done the year prior to planting, but costs are shown in the first year. https://coststudyfiles.ucdavis.edu/uploads/cs_public/6b/03/6b031624-035f-4ca4-946a-9b8ef990a00e/97almsjv.pdf

 

Climatic requirements #

In a few words, the almond tree thrives in hot and dry climates, but it also has certain needs in cold (250-350 and in some varieties 500 hours), and that’s why it cannot be cultivated in tropical climates. Due to the fact that it blooms very early compared to other fruit trees (during February in US), it can be harmed by frosts during this period, and this is the main limiting factor when growing almond trees.

Low winter and spring temperatures and very high summer temperatures inhibit growth and fruit set. During flowering, temperatures below 24,8 °F (-4 °C) for half an hour and longer can cause serious damage, depending on the variety. On the other hand, very high summer temperatures when accompanied with low soil moisture can result in the shrinkage of almond. The needs of almond in cold (in order to break the dormancy of the buds) are small, about 250-350 (and in some cases over 500) hours of exposure to temperature less than 45 °F or 7 °C. This is the reason why the almond tree blooms earlier than most of fruit trees and thrives in areas with mild winters. The long and warm growing season favours the fruit ripening. Frequent rainfalls and cold weather during the flowering deteriorate the cross pollination activity of bees, resulting in decreased fruit set and production. Moreover, rainfall and humid conditions favour the development of fungal and bacterial diseases, and thus reduce production. The greatest yields are often achieved in irrigated almond orchards that are located in areas with long and hot summer, without many rainfalls. In United States, the perfect climate for growing almond trees can be found in Central California. There are also other suitable areas (some parts of Arizona, Texas and Georgia), but as a rule of thumb, the risk of fungal diseases increases as we move to the east. Outside US, the perfect climate for growing almond trees is the one found in Mediterranean countries (Italy, Spain, Morocco, Greece and Tunisia). However, almond trees are also grown with great success in Syria, Iran and Australia.

 

Soil requirements #

Like all fruit trees, almond tree prefers full sun and well-drained soil. The almond tree thrives in a wide variety of soils from sandy loam to sandy clay, but generally prefers light, fertile, deep and well drained soils. Although the almond tree is resistant to drought and can survive for many years in dry soils, the production is significantly reduced under such conditions. Low soil moisture at the end of the growing season is less critical than in the beginning. Heavy or not well drained soils should be avoided, because they have been found to decrease production and favour the spread of various fungal diseases. Soil pH is normally not a limiting factor, as the tree can grow well in pH ranging from 5,5 to 8,5. However, most professional almond growers fix soil pH around 6,5 to 8 (ask a licensed agronomist).

 

Before planting the young almond trees, the soil has to be ploughed at a depth of 20-27 inches (50-70 cm). Tillage aims at the destruction of perennial weeds and soil fluffing, which is necessary for the development of the root system. Before ploughing, almond farmers often take soil samples and send them to laboratory, in order to determine any necessary corrective actions. Many almond farmers add 20-30 tons of manure per hectare well before planting the young trees, so as to increase soil fertility and improve soil texture. https://wikifarmer.com/almond-tree-soil-requirements-and-preparation/

 

Varieties #

Two types of almonds can be distinguished, those with soft shell, mainly produced in California, and those with hard shell, like the Spanish varieties Marcona and Desmayo or many of the produced in Portugal.  Different types of almonds can be distinguished according to their taste and uses. The “sweet almonds”, consumed as dry fruit may have soft or hard shells; the ” bitter almonds” have a strong bitter flavour due to a glucoside called amygdalin (in sweet almonds it disappears almost completely when they mature); they are used in the food and agriculture industry to obtain oil, for instance. The green almonds have not undergone the fruit set.

Classifications are based on the hardness of the shell; thus, in Spain there are almonds with soft shell like the ” Mollar de Tarragona ” and ” Fitas” from Ibiza, which are very appreciated in the European markets thanks to their exquisite flavour, colour and presentation. The most important hard shell commercial varieties are Marcon , Planeta, Llargueta, Rumbeta, Doble Fina and Desmayo. In Spain, many local varieties are produced in each region, among which stand out Marcona and Desmayo largueta. Nevertheless, other foreign varieties with late flowering have spread, like the Italian “Tuono” and “Cristomorto’ or the French “Ferragnès” and “Ferraduel“. There are some types without a specific denomination that come from seeds with the generic name ” Comunes”. Some new varieties obtained in Spanish improvement programs have also spread, highlighting Masbovera and Guara.

In France, the almonds with soft shell are known from the old times as ” princesses” or ” fines”; the semisoft ones are called ” amandes des dames” and those with hard shell are the ‘beraudes”, ” molières” or ” caillasses” . Some varieties cultivated in France are Ai, Ardechoise, Sultana, Beautiful of Aurons, Ferragnès, Ferraduel, Ferralise and Ferrastar, among others.

The almond tree cultivated in Portugal usually produces almonds with hard shell. The varieties have different earliness in respect to the flowering. Some varieties are Boa Casta (average earliness), Pretty (late), Pretty St. Bras (early), Casa Nova (very late), Duro Amarello (quite early), Duro de Entrada (quite early), Gama (quite early), Jose Dias (average-early), Marcelina Grada (quite early), Mourisca (very early), Parada (quite early) and Verdal (average-early).

In Italy, the varieties are classified according to their place of origin: those coming from Puglia and from Sicily, the main almond tree production locations in Italy. The varieties of Puglia are Tuono, Filippo Ceo, Genco, Cristomorto, Fragiulio, Rachele, etc. The Sicilian varieties are d”Avola Pizzuta, Fasciuneddu, Romana, Avola R. 40, Cavaliera and Bonifacio.

In California, the greater production is soft shell almonds. Some varieties, from the oldest to the most recent ones areNonpareil, IXL, Ne plus ultra, Texas, Davey, Tardy Nonpareil, Thompson, Ballico, Merced, Ruby, Carmel, Butte, Price, etc. Some of them are the result of crosses between them, that is to say, they are hybrids.

#

Descriptions of Some Almond Varieties

” Mollar de Tarragona’ 
Quite big, wide, of more or less dark brown colour, slightly rough. 40-43% yield on shelling and 5% of double almonds. Average time of flowering, produced in Spain. #

” Marcona’
Quite a large almond, of round shape, slightly rough. 25-28% yield on shelling; no double almonds. Flowering at the beginning of March and late maturation at the beginning of October. It is original from the province of Alicante (Spain).

” Desmayo Largueta’
The tree is of hanging growing habit. There are several local types in the Spanish regions, the most well-known is Desmayo Rojo. Extended, pointed, smooth almond with a hard shell, commercialized under the name of ” Larguetas”. Very precocious flowering and very late maturation. It is cultivated in all the Ebro valley, from Zaragoza to Tarragona, and in the bordering provinces of Lérida and Teruel (Spain).

” Tuono’ 
Hard shell fruit. When ripe, they maintain the peduncles of the fruits on the tree. 30-40% yield on shelling; the proportion of double almonds varies between 15 and 30%. Very late flowering and early maturation. Variety of Puglia (Italy).

” Ferragnès”
Fruits of quite large size, slightly pointed and of brown skin, not very rough. Very late flowering and maturation at the end of September in the region of Nimes (France). It originated from ” Cristomorto’ x “Ai’, in France.

” Ferraduel”
Hard, wide and flattened shell, with thin, dark brown skin. Very late flowering and maturation at the end of September in the region of Nimes (France). It originated from “Cristomorto x “Ai’, in France.

” Ferralise’
Small, thick, clear and very smooth almond. Hard shell, 30% yield on shelling. Very late flowering. Original from the cross ” Ferragnès” x ” Ferraduel”.

” Bonita’
Medium size almond, thick, pale colour, stripped, very attractive. 23% yield on shelling. Late flowering. Portuguese variety.

” Casa Nova’
Great almond, flattened, quite rough. 20% yield on shelling. Later flowering than other Portuguese varieties.

” Parada’
Quite large, wide, dark brown almond, slightly rough but highly appreciated in Portugal for its shape. 19-22% yield on shelling. Quite early flowering.

” Verdal”
Quite large an almond, flattened and with a very good taste. 24% yield on shelling. Early flowering. Portuguese variety.

” Nonpareil”
Slightly elongate, thick almonds, with very pale and thin skin. The shell is also very thin. 60-65% yield on shelling. Very early maturation. It is the classic Californian variety.

” Ne plus ultra’
Known as ” Neplus”. The appearance of this fruit in the shell is attractive, elongate and clear, but the almond is long and flat, usually with folds and wrinkles. 55-60% yield on shelling. Early flowering and spread out over a long period of time. Californian variety.

” Texas”
Thick fruit. Late flowering and maturation in the middle of October, in Nimes (France). Its origin is California. http://www.frutas-hortalizas.com/Fruits/Types-varieties-Almond.html

 

Planting #

When planting a new orchard, precautions should be taken to prevent tree loss. Care should be taken to reduce direct damage to the trees. Trees should be planted as soon as possible once received from the nursery. Always cover bare roots with a tarp when transporting trees on back of a trailer, making sure to keep the roots moist. If the trees are heeled in, fumigated soil or sawdust should be used and excess moisture should be avoided. Cold storage should be avoided if possible. If cold storage is necessary, then trees should be fully dormant and the roots kept moist.

Care should be taken to ensure that trees are properly planted. In heavy soils, planting on berms is recommended to help drain water away from the crown of the tree. Berms should be pulled before planting to ensure that the graft union is above the soil. Do not pull a berm after planting as this may cover the graft union. Planting depth after settling should be no deeper than in the nursery and the graft union should always be well above the soil line. Holes should be dug deep enough to accept the root system; no deeper. If a crust or soil glaze occurs, break up or slice to ensure proper root growth.

Planting trees high will help reduce losses to the root disease Phytophthora. The only exception is trees grafted to Marianna 2624 plum rootstock; they should be planted at the same depth they were at the nursery to avoid suckering from the roots.

 

When planting, try to follow some of these tips:

• Dig a hole deep enough so the roots are spread out and not cramped.
• Plant the trees so that the nursery soil line is above the current soil line.
• Plant the highest root a little above the soil line and cover it with extra dirt.
• When planting, allow for 3-6 inches of settling in the planting hole.

 

Upon planting, soil should be tamped firmly with the foot to eliminate air pockets. Be careful not to break any roots. After planting, trees should be tanked in with 1 to 3 gallon of water unless the soil is very moist. This water will help moisten dry soil and fill in small air pockets. Avoid over irrigation as excess water may cause saturated conditions that kill small roots due to poor aeration and/or the root pathogen Phytophthora. More water should be used if trees are planted late during warm weather, planted in dry soil, or if the soil cannot be tamped firmly around the roots due to soil conditions. Keep in mind that a rain immediately after planting does not provide enough water to settle the soil around the root system.

 

Fertilizers should not be applied until after the trees leaf out. Apply small amounts of fertilizer, no more than 1 ounce of actual nitrogen, frequently throughout the first growing season. If using granular fertilizers, make sure that they are applied within the wetting pattern of the irrigation system. Avoid applying fertilizers to the trunk of the tree to prevent burning. Never apply fertilizers to the planting hole as this may burn back fine feeder roots.

Careful planning and preparation from the beginning will yield a good return for the efforts applied. Mistakes made at the beginning of an orchard will be present for the duration of the orchard’s life. This is one of the times in which effort or expense should not be spared. http://www.westernfarmpress.com/tree-nuts/proper-almond-tree-planting-methods

 

Fertilizer Application #

Mature bearing trees:

Nitrogen

In almond trees, nitrogen is needed to renew and invigorate fruiting wood. Also, it is needed for fruit growth and development. The greatest need for nitrogen occurs when the almond trees came into production. At this time, the demand for nitrogen is due to fruit development, foliage formation and tree storage in roots and branches. We must meet the tree demand for nitrogen, since a shortage of this element can reduce yields.

Most of the nitrogen applied to an almond orchard becomes part of the kernel, hull and shell. Therefore, the projected yield of the orchard can be used to estimate the need to replace nitrogen removed in the crop. Apply approximately 33 gr of nitrogen for each 326 gr of projected Kernel (meat) yield.

Over-fertilization can lead to excessive vegetative growth, which can create shading for fruiting wood. Furthermore, over-fertilization will increase production costs and will lead to water contamination.

 

Maximize Efficiency: 

• Apply N only when leaves are present and the tree roots are active.
• Apply a uniform irrigation that is adequate to carry the N into but not past the root zone.
• At young nonbearing trees apply nitrogen as long as irrigation continues.
• Mature trees need most of the N in early spring, therefore, a late summer application of part of the N before an irrigation will provide the tree with N for early spring growth. The rest of the N needed should be applied during the spring.
• Fertigation is very efficient in N applications.
• Analyze leaves to fine tune N level to the orchard. Maintain the level in the adequate range. Application reaches 200-250 kg of N/ha. Post harvest application of 50 kg/ha is also recommended. 2.5 -3.0 % out of D.M in tissue analysis.

 

Potassium

Almond kernels contain 0.75% K (USDA data); and potassium represents more than 2% of the dry weight of almond hulls (Calixto, 1982). Among soil-derived nutrients, potassium and nitrogen are removed in the greatest quantities. Leaf analyses are usually performed on leaves sampled when nutrient concentration is relatively stable. However, analysis this late in the growing season allows the grower plenty of hindsight, but scant opportunity to correct deficiencies.
Application of 250 kg of K (elemental), 1.4% out of D.M in tissue analysis.

 

Phosphorus

Application will follow according to tissue analysis.

Foliar Nutrition –  It is recommended to spray:

• 1% Poly-Feed™ 20-20-20 or 23-7-23 or 21-21-21 foliar nutrition in 3 cycles during fruit set. First spray should be applied after flower petal fall and two additional with an interval of 7-10 days between application. These foliar applications correct transient nutrient deficiencies due to strong temporal demand for macronutrients and possible weak uptake by roots in the early spring time.
• 2%-4% Haifa Bonus 13-2-44 during kernels filling, two sprays with an interval of 7-10 days.

 

Boron

2 kg/ha B when deficiency occurs. Boron deficiency may be a problem in any orchard on sandy soils and/or where irrigation water is low in B, causes the following problems:

• Low nut set
• Excessive nut drop
• Malformed nuts
• Undesirable vegetative growth

Foliar B should be applied al early post-harvest, which is more effective than spring or dormant sprays. Sprays at hull split may also be effective, but have not been sufficiently tested. In California, B toxicity (leaf B 87 ppm or more) and deficiency both present problems.

 

Zinc

Zn deficiency is controlled with sprays of 19-29 g ZnSO4/l in the dormant period and by foliar sprays of 6 g ZnO/l applied in mid-season.

 

Young non-bearing trees:
Better to be followed by N and K at the same ratio for better uptake of nitrogen.
First year – 100 – 150 gr N/tree.
Second year – 200 – 300 gr N/tree.
Third year – 350 – 500 gr N/tree.

 

Tissue analysis

Macro elements

Microelements

http://www.haifagroup.com/knowledge_center/articles/haifa_articles/almond_fertilizer/

 

Common Pests and Diseases #

Almond leaf scorch; golden death
Xylella fastidiosa

Symptoms

Chlorotic leaf margins; necrosis of leaf margins beginning toward tip of leaf and spreading to base; patches of necrotic tissue with chlorotic margin

Cause

Bacterium

Comments

More of tree will be affected each year; bacterium can infect rye, blackberry and nettle and if these plants are nearby they may act as reservoir; transmitted by leafhoppers and spittle bugs

Management

If discovered early (while disease affects only one branch) disease can be removed by pruning primary scaffold 5 to 10 ft below symptoms; older infections may require the tree to be removed and replaced

 

Crown gall
Agrobacterium tumefaciens

Symptoms

Galls of various sizes on roots and root crown below the soil line; galls may occasionally grow on the trunk; galls are initially light coloured bulges which grow larger and darken; galls may be soft and spongy or hard; if galling is severe and girdles the trunk then young trees are weakened due to constricted vascular tissue; trees may be stunted and rarely die

Cause

Bacterium

Comments

The bacterium enters host plants through wounds and causes plant cells to proliferate and cells to be undifferentiated, leading to the formation of a gall

Management

Only plant disease-free nursery stock; plant trees in well-draining soils; avoid wounding the plants as much as possible; fresh wounds can be treated with a biocontrol agent (Agrobacterium tumefaciensK84), if available, to prevent the bacterium colonizing

 

Alternaria leaf spot
Alternaria alternata

Symptoms

Light brown lesions on leaves which expand to form circular lesions on leaf blade or semi-circular lesions on margin; leaves may develop light yellow necrosis which dries and turns tan in center of leaves; infected leaves dropping from tree; fruit does not drop from tree

Cause

Fungus

Comments

Disease emergence favors warm weather

Management

Late spring treatment with appropriate fungicide if Alternaria symptoms are present

 

Anthracnose
Colletotrichum acutatum

Symptoms

Blighting of blossom; dieback of limbs; death of foliage with leaves remaining attached; nuts with orange lesions

Cause

Fungus

Comments

All cultivars susceptible; occurs more often in warm, wet conditions

Management

Fungicide treatment and cultural practices required to control disease. Orchards with a history of anthracnose infections should be sprayed at 5-10% bloom and applications should be repeated every 10 to 14 days; dead infected branches should be pruned; low angle nozzles should be used in orchards with spray irrigation to prevent wetting of leaves

 

Hull rot
Rhizopus stolonifer
Monolinia spp

Monilia on a tender fruit Almond

Symptoms

Tan lesions on hulls which enlarge and cause fruit to shrivel; dark gray spore masses visible between hull and shell; leaves in proximity to infected fruit may wither and curl; leaf death occurs on side of shoot closest to infected fruit

Cause

Fungus

Comments

Hulls of fruit are susceptible to hull rot until they are dry

Management

Management of irrigation should be practiced. Reduce irrigation at hull split; demethylation inhibitor and quinone outside inhibitor fungicide may be applied in combination with irrigation management

 

Brown Rot Blossom Blight
Monolinia laxa

Symptoms

Blighted blossoms; stigma and anther of flowers turning brown and necrotic; blossom collapsing and turning brown; light brown powdery fungal masses may be visible on infected flowers; gummy exudate at base of flowers; cankers forming on twigs associated with blossoms

Cause

Fungus

Comments

Disease emergence favors frequent rainfall during bloom

Management

Fungicide application at 5-10% bloom and full bloom to protect flowers; one application at full bloom usually sufficient if there is no rainfall; two or three applications should be made if bloom is accompanied by rainfall

 

Shot hole
Wilsonomyces carpophilus

Symptoms

Circular purplish spots on foliage which enlarge and turn chlorotic then tan; drying of lesions causes missle of lesion to drop out of leaf causing small holes to develop

Cause

Fungus

Comments

Spores transmitted in water; disease more common in wet conditions

Management

If fungal fruiting structures are present in Fall (visible under a hand lens as small black spots in the center of lesions) then a fall treatment with fungicide is required; fungicide should be applied before wet periods to protect tree

 

Verticillium wilt (Blackheart)
Verticillium dahliae

Symptoms

Leaves on one side of tree turning yellow; wilting early in season

Cause

Fungus

Comments

Fungus overwinters on soil, recurring each year; problematic if orchard is interplanted with other susceptible plants e.g. cotton, tomato, melon

Management

Orchards should not be intercropped with susceptible plants e.g. cotton, tomatoes or melons; solarization or fumigation of soil prior to planting may be used to kill fungi in soil

 

Pavement ant (Southern fire ant)
Tetramorium caespitum
Solenopsis xyloni, S. molesta

Pavement ant

Southern fire ant

Symptoms

Hollowed out nuts on ground

Cause

Insects

Comments

Prevalent in orchards using drip or spray irrigation

Management

Monitor orchard for ants in April and May; apply ant baits before harvest to manage high ant populations; remove nuts from orchard floor as soon as possible

 

Almond brownline and decline
Peach yellow leafroll mycoplasma

Symptoms

Stunted tree growth; drooping/wilting of leaves; brown necrotic areas under bark

Cause

Phytoplasma

Comments

Most common on young trees; grow trees from pathogen free stock

Management

Stunted trees should be removed and replaced; plant only certified pathogen free trees

 

Almond kernel shrivel
Peach yellow leafroll phytoplasma

Symptoms

Late blooming; new growth stunted; paler, smaller leaves; kernels of nuts shrivelled at harvest

Cause

Phytoplasma

Comments

Most common where peach rootstock has been used for grafting; remove infected trees

Management

Remove diseased trees; plant only certified trees. https://plantvillage.org/topics/almond/infos