Avocado Tree Water Requirements and Irrigation Systems

Avocado Water Requirements

A sufficient and well-distributed water supply is vital for a healthy avocado orchard that can offer sustainably high yields for many years. Since avocado is native to the humid subtropical and tropical regions with abundant rainfall, crop cultivation in different climatic zones and environmental conditions may need extra irrigation to cover the plant’s water requirements.

After transplanting, the farmer can create a basin around each tree to collect water from rain or irrigation. The grower can regularly water the newly planted avocado trees until they are established. The amount and frequency of irrigation will change as the trees mature.

In my fields in Crete (Greece), winter rainfalls are sufficient to cover the water needs of avocado trees during that period. However, during summer, I apply irrigation through drippers once every ten days, for 1-2 hours. While this practice is efficient for my orchards, I advise other avocado growers to form specialized irrigation schedules for their fields.  

How much water does an avocado tree need?

Avocado is considered a water-intensive crop. The exact amounts of water needed depend on the environmental conditions, the soil characteristics, and the age of the trees. Generally, a mature tree needs at least 1,000-1,300 mm (40-50 in) of rain per year (1). In Mediterranean climates, a single tree may require up to 51 mm (2 in) of water per week during the dry and warm summer months. More specifically, based on scientific data, in hot climates, avocado water use is around 45 liters per day (l/day) in spring, 136 to 220 l/day during summer, and 121 l/day in autumn (2, 3). The avocado tree has shallow roots that are spread mainly in the top 20-60 cm of soil and are not very efficient in exploiting water from deeper soil layers. As a result, rainfalls and/or irrigation should keep the soil’s upper 15-20 cm (6-7 in) moist (4).

These amounts should be delivered to the plants in smaller quantities with more frequent irrigation sessions. However, the farmer should know that too frequent light irrigation may encourage shallow root system growth, making the plant less tolerant to drought and strong winds. Flooding is not desirable as it promotes root rot as well as water and nutrient runoff and should always be avoided, in my opinion.

When and how to irrigate an avocado tree? 

Avocado trees have large soft leaves and evaporate a lot of water in warm weather, so they need regular watering (5). The most critical periods are the flowering and fruit set. During these growth stages, the farmer should interfere with irrigation if the rainfalls are insufficient to reduce fruit drop and increase the final fruit size (3).  

For determining the frequency of irrigation sessions, the farmer should take into account the:

• Local and seasonal environmental conditions. In areas with long, dry, and warm summers, irrigation may be needed every 7-10 days during summer. While, in most cases, winter rainfalls can cover the water plant needs, it is best to irrigate if there are long dry spells and the soil has dried out. Many farmers use mulching (green manure) as soil cover to preserve the soil moisture.
• soil characteristics (e.g., more frequent irrigations with fewer water quantities in sandy soils)
• the acceptable stress level that the trees will experience
• availability of water

Best irrigation systems for avocado trees

The main two irrigation systems used successfully in avocado farming are drip irrigation and low-volume sprinklers. You may irrigate your trees using a drip system with either two to four emitters per tree or small micro-spray emitters (2). To have the best results, it is advised to place the drippers on the ground close to the active root systems (at the limits-projection of the canopy). As the tree grows, remember to change the position of the drippers as well. In orchards where a drip irrigation system is used, the farmers can choose to fertilize their trees using fertigation (= fertilization + irrigation, i.e., water-soluble fertilizers injected into the irrigation system). If you choose this system, you may prefer a single trunk training system for your trees, with a higher canopy that does not interfere with the water distribution. On the other hand, sprinkler irrigation has been reported to improve the fruit size and oil percentage (6).

Avocado trees are sensitive to high soil salinity. For this reason, irrigation water quality plays an important role. Water with less than 100 ppm of chloride salts is suitable for avocado farming (7). High iron concentration (more than 1 milligram per litre) in the water can also create significant problems for avocado growers. This is more common when using underground water resources (4).

As mentioned above, each field is different. To form a more suitable irrigation schedule, the farmer can use various instruments to assess the moisture level accurately and determine readily available water. Some cost-effective techniques include using simple technology like tensiometers or porous blocks that can help a grower decide when and how much to irrigate (8, here).

References

1. https://www.californiaavocadogrowers.com/cultural-management-library/irrigating-avocado-trees
2. http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/CULTURAL/citruswatering.html
3. http://www.avocadosource.com/journals/saaga/saaga_1991/saaga_1991_pg_91-93.pdf
4. https://www.agric.wa.gov.au
5. https://www.jica.go.jp/project/english/kenya/015/materials/c8h0vm0000f7o8cj-att/materials_02.pdf
6. https://www.fao.org/3/X6902E/x6902e06.htm
7. https://www.elgo.gr/images/ioanna/periodiko/Teyxos_22/AVOCADO.PDF
8. https://www.californiaavocadogrowers.com/cultural-management-library/assess-avocado-grove-irrigation-methods

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