Growing avocados - irrigation principles

Page last updated: Monday, 14 January 2019 - 8:32am

Please note: This content may be out of date and is currently under review.

Fertigation

Fertigation is the delivery of fertilisers, or plant nutrients, to your trees via your irrigation system. Many avocado growers have set up fertigation systems as part of their irrigation systems. This requires specialised equipment and careful design.

Frost mitigation

Under tree mini-sprinklers can be used to help reduce the impact of mild frost events (see ‘Growing avocados – frost’ for more information on frost). Water by nature is more than 0°C, so by distributing this under trees you are providing warmth to the surface. Also, as water freezes it gives off heat, so by providing water to freeze, you are generating heat. However, water cannot flow when it is frozen, so any under-tree irrigation systems must be started before the temperature gets to a point where the water freezes in the pipes or emitters. Most growers have these automated with temperature sensors and operate short bursts of irrigation through the orchard until the temperature rises again. The temperature sensor must be located at the coldest point of your orchard.

Excess irrigation

We have emphasised the point of avoiding moisture stress and that avocado trees require a plentiful supply of irrigation and this needs to be applied at regular intervals. It is equally important to highlight that the avocado tree is also highly susceptible to water logging. Avocado trees are reported to start to show signs of root damage after just 24 hours of water logged soil. This is due to a lack of oxygen in the soil when it is saturated. The heavier your soil (the higher the clay content), the greater the likelihood you have of having extended periods of saturated soil. This is due to the slower infiltration rate of heavier soils resulting in the water taking longer to drain away. The other major danger of excess irrigation is that such conditions can be highly favourable to the development and spread of Phytophthora cinnamomi, or die back. This fungal like water-mould thrives in moist, warm soil, plus trees that are stressed as a result of water logging are much more susceptible to attack. Therefore, it is important to let the soil dry to your chosen refill point rather than irrigating too frequently.

Irrigation and the environment

Water is a limited commodity, so we should be aiming to waste as little as possible. Careful irrigation has less impact on the environment. Over watering is not only wasteful, but expensive due to increasing power cost for pumping and can impact on the environment. Excess leaching combined with fertilising can result in sub soil acidification and also ground water pollution in extreme cases.

Acknowledgement

This article has been adapted in part from ‘Irrigation requirements of avocado’ (Farmnote 42/88) by Bob Paulin. David Williams was also involved with the authorship of this webpage.

Contact information

Declan McCauley
+61 (0)8 9777 0184