AVOCADO- Agronomy

Back to > Major Fruits | Minor Fruits | Underutilized Fruits

Avocados do well in the mild-winter areas ofCalifornia,FloridaandHawaii, but thrive inMexicoall year. Avocados do best some distance from ocean influence but are not adapted to the desert interior. West Indian varieties thrive in humid, tropical climates and freeze at or near 0° C. Guatemalan types are native to cool, high-altitude tropics and are hardy -1.1 to  4.5° C. Mexican types are native to dry subtropical plateaus and thrive in a Mediterranean climate. They are hardy -4.5 to -7.2° C. Avocados need some protection from high winds which may break the branches.

Soil: Avocado trees like loose, decomposed granite or sandy loam best. They will not survive in locations with poor drainage. The trees grow well on hillsides and should never be planted in stream beds. They are tolerant of acid or alkaline soil. In containers use a planting mix combined with topsoil. Plastic containers should be avoided. It is also useful to plant the tub with annual flowers to reduce excess soil moisture and temperature. Container plants should be leached often to reduce salts.

Propagation:Desired clonal rootstocks can be propagated by a method known as the etiolation technique. The largest seed are planted in gallon cans and the seedlings are then grafted to a root rot tolerant clonal scion. When the stem of the graft reaches about 1/4 inch in diameter, the top is cut off leaving a whorl of buds just above the graft. A 4 inch band of black tar paper is formed into an extension of the can and filled with vermiculite and placed in a dark box with high temperature and humidity. When growth is some 3 – 4 inches above the vermiculite, the plant is removed into the light where the upper portion quickly assumes a green color. The tar paper collar is removed; the shoot is severed from the seed and then placed in flats where the cuttings are rooted in the conventional manner. Any seed may also be used for rootstock, but Mexican types make the strongest growth and are the most often used. Plant cleaned seeds as soon as they are ripe. The seedling plants are ready to bud the following year. Budding is done when suitable buds are available. Larger stocks are worked by bark grafts in the spring. Scions are collected after the buds are well-formed. Paint and cover the graft with a moistened plastic bag and place a vented paper bag over the whole.

The selection of a suitable site is of the utmost importance. Avocados are extremely susceptible to the root rot fungus Phytophthora cinnamomi. No avocado rootstock is completely resistant to this disease. Surface and subsoil drainage must be excellent. Sloping ground with a porous top soil structure may be unsuitable if clay bands or hard pans prevent the free flow of water through the soil. Checking the profile with soil pits to a depth of about 2 m is a pre-requisite. Natural vegetation can indicate localized soakages and high water tables. Steep gradients, particularly where trees are planted in banana plantations make harvesting and other management operations difficult. Such areas are susceptible to erosion. The preferred aspect is a slope facing north to east. Plantings on these slopes with rows running north-south maximizes sunlight inception.

Avocados are grown on a wide range of soil types from free-draining, red basaltic loams, previously supporting rain forest, to eroded coastal sand dunes. Where soil depth is marginal (less than one meter), mounding along the row is employed to increase the effective root zone and improve drainage. Prior to planting a new orchard it is recommended that any tree stumps or large roots be removed to reduce the risk of root rot developing and spreading to young trees. The pH of the soil should be checked and adjusted to about 5.5 with lime or dolomite if necessary. Liming materials should be applied before the final cultivation to ensure that they are well incorporated into the soil. Deep ripping is recommended to improve sub-surface drainage. Zinc is the most common trace element deficient (e.g Australian soils) and if required is also incorporated during final soil preparation.

Individual tree sites are prepared by hand about 3 months prior to planting. At each planting site 200 to 300 g of superphosphate along with 10 to 15 l of poultry manure are dug in to a depth of 300 mm over a one square meter area. The ‘Pegg philosophy’ – cover-cropping and mulching as an integral part of root rot control – is practised by a significant proportion of growers in subtropical areas during the establishment phases of the orchard. Invariably these properties have higher productivity.

The cost of establishing an avocado orchard can be high, and this investment can be jeopardized if sound planning and management strategies are not adopted. The first activity is to take a soil sample for chemical analysis and then apply the nutrients that are recommended. It may take longer than one year to correct a soil nutrient imbalance. Protection from strong winds is essential. Permanent windbreaks around boundaries and along crests should be established as early as possible, even 3 to 4 years before planting the orchard. Internal windbreaks are used to dissect the orchard into sheltered bays. These windbreaks are generally removed when the trees are about 4 years old. Control of phytophthora root rot is essential. Two main principles apply:

• Excellent surface drainage. This is particularly important in high rainfall areas where, after heavy rain, water will pond in slight depressions and threaten nearby trees. On gently sloping land, trees are planted in rows running up and down the slope. It is desirable to form mounds for each tree row, so that water quickly drains away from trees and then flows down the interrow space. This also gives a deeper layer of top soil for the tree roots.
• High levels of organic matter. Mounding, although it is an expensive operation, can mean the difference between tree survival and tree death.

A program of green manuring may be desirable before planting. After planting, aim at maintaining these high levels of organic matter, so that the soil condition resembles that of natural rainforests. Under these conditions Phytophthora root rot caused by Phytophthora cinnamomi (a major international disease of avocado and is present in all countries producing this crop) is suppressed biologically. All areas inAustralia producing avocados are affected by this disease. It is successfully controlled by trunk injection with potassium orthophosphonate using a 20% a.i. solution which is injected at the rate of 15 ml per m of tree diameter. Despite the spectacular success of phosphonate treatments, an integrated approach of biological and chemical control is still recommended in the high-risk subtropical areas. Anthracnose, a serious fruit problem in most environments, is controlled by regular spraying with copper-oxychloride and a post-harvest treatment of prochloraz (Sportak). Verticillium wilt is a soil-borne disease which attacks the vascular system but seldom kills plants, and there is no effective fungicidal treatment. Therefore, it is a disease of lesser significance. Green manure cropping is important during the establishment phase. It prevents erosion, increases soil organic matter and facilitates settling. In later years, the area can be sown to permanent sod.

Irrigation requirement:

Avocado trees may not need irrigation during the winter rainy season, but critical for prolonged mid-winter dry spells. Avocados are very sensitive to moisture stress, especially during flowering, fruit set and fruit development. The avocado is a tree of rain forest origin and requires regular watering to maintain high yields. Water monitoring is by either tensiometers or the more sophisticated electronic monitoring devices that provide a continuous picture of the water status of the root zone. When using tensiometers it is usual to maintain soil metric potential between -40 and -10 kPa at 300 mm depth.

Most orchards in Australia have undertree mini-sprinklers to supplement rainfall and to apply nutrients to the trees (fertigation).Water use during the winter months is reduced but there is a rapid increase in requirement as the trees come into flower during early spring. Water stress during the first eight weeks of fruit growth can lead to reduced fruit size as cell division is retarded. Also, water stress during the natural period of fruit drop at the end of spring, can increase fruit loss, thereby reducing final yield. Ring-neck, a natural cincturing of the pedicle, has been related to water stress during the later stages of fruit maturity, and can reduce fruit size and final yield. Therefore, during these critical periods the soil profile should not be allowed to dry out and tree requirements should be monitored, for example using tensiometers.

InPhilippines, the practise of irrigating avocado trees in the country is uncommon. The plants are irrigated only when they are newly planted in the field and at certain times of the year when the dry season extends from four to five months. Otherwise, the trees are rainfed. Irrigation is effected manually.

InChina, avocado sets flowers and bears fruit during December to May,  hence irrigation is very important for a high and stable yield. For the orchards with easy access to water, flooding is achieved by water pumping, whilst for the orchards far away from water source, irrigation is carried out using tractors with water tanks.

InVietnam, ground water is the main source for irrigation in the highland areas. Therefore, wells can be found in most farms. Moreover, to limit the water loss through evaporation during the four to six months of dry season, the tree basins are mulched with weed residue, banana leaves, straw, etc. Sprinkler irrigation has been reported to improve the fruit size and oil percentage; also, it advances harvesting time inIndia. Therefore, irrigation at intervals of three to four weeks during the dry months is beneficial to avocado. To avoid moisture stress during winter season, mulching with dry grass/dry leaves is desirable. Flooding is undesirable as it promotes root rot incidence.

Using weekly evapotranspiration figures is another useful method. Over irrigation can induce root rot which is the most common cause of avocado failure. To test to see if irrigation is necessary, dig a hole 9 inches deep and test the soil by squeezing. If it is moist (holds together), do not irrigate; if it crumbles in the hand, it may be watered. Watch soil moisture carefully at the end of the irrigating season. Never enter winter with wet soil. Avocados tolerate some salts, though they will show leaf tip burn and stunting of leaves. Deep irrigation will leach salt accumulation.

The application dose and proportion of manures and fertilizers are generally based on the soil fertility, tree age, growth and yield. Commence feeding of young trees after one year of growth, using a balanced fertilizer, four times yearly. Older trees benefit from feeding with nitrogenous fertilizer applied in late winter and early summer. Various micronutrients (Fe, Zn, B) have profound influences on tree growth, nutrient uptake and yield of avocado. Integrated nutrient management with inorganic fertilizer, supplemented by organic manuring, is advocated for avocado. In Sikkim (India), the soil is deficient in nitrogen, zinc and boron. Therefore, application of urea is carried out in two split doses, in March/April and September/October (just before and after the onset of the monsoon) is recommended. Foliar application of zinc sulphate (0.5 per cent) may be undertaken in April-May, and other fertilizers applied in soil during March-April.Yellowed leaves (chlorosis) indicate iron deficiency. This can usually be corrected by a chelated foliar spray of trace elements containing iron. Mature trees often also show a zinc deficiency. Under the existing orchard soil conditions in the Philippines, young and nonbearing avocado trees require only nitrogenous fertilizer. Farmers apply 100-200 grams of (NH₄)₂SO₄ or about 50-100 grams CO(NH2)₄/tree, twice a year. As the trees bear fruit, 500 grams of complete fertilizer are applied, twice a year. For full-bearing trees, two kilograms of complete fertilizer are applied per year. A supplemental application of organic fertilizers, e.g. animal and poultry manure, and compost, is also given. The fertilizer is applied at the onset and towards the end of the rainy season. It is usually applied in a ring around the trunk of the tree or in shallow holes dug beneath the tree canopy.

Training and Pruning:

There is little tree training practised on avocados during their establishment years apart from tipping the central shoot to encourage branching. Tipping growing points of trees in their second year to increase tree complexity is carried out by some growers but there is little evidence of benefits. Columnar cultivars require pinching at early age to form a rounded tree. Others need no training. Controlling tree growth in mature orchards remains the biggest challenge of orchard management. Being terminal flowering trees, avocados need to grow each year in order to remain productive, hence trees become larger. To maintain orchard access between rows, major limbs are periodically removed, cutting back to the main trunk. Similarly, to contain tree height major limbs are lopped from the top of the tree when necessary. In some orchards, trees are not pruned at all until their size is so big that they are uneconomic to manage. They are then stumped to approximately one meter high and allowed to re-grow. After this treatment they are back in full production within two years. The best results are obtained by fencing the tree with plastic mesh for the first two to three years. The skirts of avocado trees are sometimes trimmed to discourage rodents, otherwise the trees are usually never pruned. Branches exposed to sun by defoliation are extraordinarily susceptible to sunburn; such branches should always be whitewashed. Most cultivars are ill-adapted to espalier because they are too vigorous.

1. Adame, E.L. 1994. Plagas del aguacate y su control. IV Curso de Aprobación Fitosanitaria en Aguacate. Facultad de Agrobiología. U. M. S. N. H. Uruapan, Michoacán, México.
2. Armstrong, WP (2000). “Fruits Of The Rose, Olive, Avocado & Mahagany Families – Laurel Family: Lauraceae Extract from: http://waynesword.palomar.edu/ecoph17.htm#avocado
3. “Avocados, raw, California”. NutritionData.com (2007). Retrieved on 2007-12-29
4. Bailey, B.J., and P.M. Hoffman. 1980. Amorbia: ACalifornia avocado insect pest. Department of Entomology,University ofCalifornia, División of Agricultural Sciences. Leaflet 21256Riverside, Ca.U.S.A.
5. Boyle, E.M. (1980). Vascular anatomy of the flower, seed, and fruit of Lindera benzoin. Bull. Torreya Bot. Club. 107:409-417.
6. Bravo, M.H., et al., 1988. Plagas de frutas. Centro de Entomología y Acaralogía , Colegio de Posgraduados. Montecillo, México pp 49-236
7. Bruno Razeto, Jose Longueira, and Thomas Fichet. (1992). Proc. ofSecond World Avocado Congress 1992 pp. 273-279
8. California Avocado Comission (2007). Avocado.org. Retrieved March 1, 2007, Web site: http://www.avocado.org/
9. Davenport, T.L. Avocado Flowering, Hort. Reviews 8: 257-289.
10. Dowling, Curtis F.; Morton, Julia Frances (1987). Fruits of warm climates. Miami, Fla: J.F. Morton.
11. “FATTY ALCOHOLS: Unsaturated alcohols”. CyberlipidCenter. Retrieved on 2007-12-29.
12. Hirokazu Kawagishi, Yuko Fukumoto, Mina Hatakeyama, Puming He, Hirokazu Arimoto, Takaho Matsuzawa, Yasushi Arimoto, Hiroyuki Suganuma, Takahiro Inakuma, and Kimio Sugiyama. (2001). Liver Injury Suppressing Compounds from Avocado (Persea americana). J. Agric. Food Chem., 49 (5), 2215 -2221, 2001. 10.1021/jf0015120 S0021-8561(00)01512-0
13. Koch, F.D. (1983). Avocado Grower’s Handbook, Bonsall Publications,
14. López, E. 1990. Manejo de plagas de palta. In the international course: “Producción, Postcosecha y Comercialización de Paltas”. Facultad de Agronomía. Universidad Católica de Valparaíso. Viña del Mar, Chile.
15. López-López, L., and Cajuste-Bontemps, J.F. 1999. Efecto del envase de carton corrugado y embalaje en la conservación de la calidad de fruta de aguacate CV. Hass. Revista Chapingo Serie Horticultura 5 Núm. Especial: 359-364.
16. Martínez, B.R., and Adame, E.L. 1987. El minador de la hojadel aguacatero, dinámica de población, biología y control. Revista: Fruticultura de Michoacán. Año II, (I), 11pp. 5-26.Uruapan Michoacán.
17. Minas K. Papademetriou (2000). Avocado Production in Asia and the Pacific. FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
18. REGIONAL OFFICE FOR ASIA AND THE PACIFIC
19. BANGKOK,THAILAND, JULY 2000
20. Naveh E, Werman MJ, Sabo E, Neeman I (2002). “Defatted avocado pulp reduces body weight and total hepatic fat but increases plasma cholesterol in male rats fed diets with cholesterol”. J. Nutr. 132 (7): 2015–8.
21. Ohr, H. D. , M. D. Coffer, and R. T. McMillan, Jr. (2003) Diseases of Avocado (Persea americana Miller). http://www.apsnet.org/online/common/names/avocado.asp
22. Ojewole JA, Amabeoku GJ. (2006). Anticonvulsant effect of Persea americana Mill (Lauraceae) (Avocado) leaf aqueous extract in mice. Phytother Res, 20(8): 696-700.
23. SAGAR Secretaría de Agricultura, Ganadería y Desarrollo Rural. 1999. Revista “Claridades Agropecuarias”, No. 65 “El Aguacate”. Enero de 1999.
24. Sánchez-Pérez, J. 2001. Aguacate en postcosecha. Boletín informativo de la APROAM El Aguacatero No. 5, http://www.aproam.com/aguacater5.htm SARH-DGSV. 1981. Lista de insectos y ácaros perjudiciales a los cultivos de México. 2a. Ed. Secretaría de Agricultura y Recursos Hidráulicos – Dirección General de Sanidad Vegetal. Fitófilo, No. 86: 1-196.
25. Scora, Rainer. W. and Bergh, B. (1990). THE ORIGINS AND TAXONOMY OF AVOCADO (PERSEA AMERICANA) MILL. LAURACEAE. Acta Hort. (ISHS) 275:387-394
26. Thorp, T.G. (1992). A study of modular growth in avocado (Persea americana Mill.) PhD.Dissertation. The University ofAdelaide,South Australia.
27. Whiley, A.W. and B. Schaffer. (1994). Avocado, p. 3–35. In: B. Schaffer and P.C. Andersen (eds.). Environmental physiology of fruit crops. vol. 2. Sub-tropical and tropical crops. CRC Press Inc.,Boca Raton,Fla.
28. Wikipedia, (2007). Avocado. Retrieved March 5, 2007, from Wikipedia Web site: http://en.wikipedia.org/wiki/Avocado
29. Yahia, E.M. 2001. Manejo postcosechadel aguacate, In: Memoria del 1er. Congreso Mexicano y Latinoamericanodel Aguacate.Uruapan, Michoacán, México. Octubre 2001.
30. Yahia, E. 2003. Manejo postcosechadel aguacate, 2ª. Parte. Boletín informativo de APROAM El Aguacatero, Año 6, Número 32, Mayo de 2003.