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Writer's pictureZander Ernst

A session with Netafim SA

Sometimes we still disregard the value of a good chat over a cup of coffee (obviously Krabbefontein) with a few experts. Something we lost post-COVID. People were traveling less and to be honest we enjoyed the quiet time focused on our thoughts. Yet, now good to check in now and then, rethink our practices, and also to exchange a few thoughts on the irrigation of avocados. We love these sessions to push ourselves towards a bit of introspection. Thanks, Hein, Jovan and Louis (Bekmar Irrigation)


Which brings me to one of our biggest discussions, and one of the most frequently asked questions:


So how much water does an avocado tree need daily?

Obviously, we can get into the details and the tech. T&C's apply, climate, soil irrigation type, etc all have an effect. But here is a different perspective on things.


The average farmer in South Africa for the last 2 decades, or more, has been using 40-80 litre/hour micro-sprinklers spaced between trees. Effectively one per tree, although they were spaced to be between trees. The most noted standard irrigation schedule would be 2-3 hours, twice a week. This was over the last few years in many cases reduced to perhaps 30-litre/hour micro's schedules between 1-2 hours in light scenarios and 2-3 hours in other cases. Many farmers still prefer this twice a week schedule with an extra day over weekends if needed to top up. **as Allesbeste we have moved to lower more frequent irrigations as we try and match soil infiltration and water usage with what we irrigate. But than can be a post for a different day. So when you look at these schedules, in essence what they tell you is on a standard cycle lets for simplicity just focus on the last mentioned 30 litre-an-hour scenario. This is then a total of 120 litres of water per week. (T&C's remember that in Tzaneen we only irrigate in theoretical lower demand times during winter - as our summer time which is our high rainfall period coincides with fruit-set to harvesting) This adds to 17 - 25 litres of water per tree per day. Taking into account that this is an acceptable irrigation schedule for young trees and that theory goes that older orchards use less water (although the trees use more), because we have less evaporation and are left with mostly transpiration, our irrigation should be less on older trees. Yet more than not, we find that this or even more water is applied even on mature orchards. We look at dead-seed as stress because of drought and often chat around the braai dictates that "I still didn't give enough water, I have so much dead seed and small fruit." Then I can not resist my favourite quote from Oom Chris Barnard: "try jy bietjie 'n hamburger onder 'n oop kraan eet wat water in jou mond spoel" (yes afrikaans again - in essence saying over-irrigation suffocates your roots an inhibits nutrient uptake in anaerobic conditions). Seeds can be dead from stress induced by over irrigation as well. Taking also into account our reliance for decades now on Phytophthora treatments - not on maintenance levels but in fact what would be regarded as annual "shock treatments" - I'm still of the opinion the average avocado farmer over-irrigates their trees.


Seeds can be dead from stress induced by over-irrigation as well.

This brings me back to the question, and hopefully the answer. André Ernst in a few lengthy discussions always told us to observe - as technical and scientific as he could get - it however always boiled down to observation. Something he also learned from interaction with the late Jan Toerien (if you don't know him, or of him visit this link) and that was also confirmed to me many times by people like Lucas McClean from Rietvlei formerly from Westfalia. Such a good practice Jan introduced at Westfalia. So back to lengthy discussions, we eventually ended up that if you told a "new-to-avos-farmer" to irrigate his young avocado trees 10 litres per day or the equivalent of that through an irrigation schedule you would achieve optimal growth and root growth.


Jip for emphasis sake, 10 litres per day per tree in other words 70 litres per week is sufficient water for avocado trees in our conditions. You might argue we are way to low, Really won't mind, the fact I can emphasise is that we are not 50% out. Some factors I can suggest looking at from our own experience and working with experts in industry and listening to their expert-opinions:

  1. Soil infiltration rates

  2. Water run-off during irrigation

  3. Touch and feel your soils regularly

  4. Your soil need balance of water and oxygen in the capillary spaces - if your soils are saturated most of the time most likely you are leaning towards less oxygen and more water.

  5. Dig up your roots, or even dig profile pits and evaluate root depth. Avocados ARE NOT shallow feeders as we use to think, if you always have shallow roots, most likely you are over irrigating.


Avocados ARE NOT shallow feeders

Today on our drip for example our standard cycle is 5-10 litre per tree on young trees per day, and this often is slightly reduced depending on ridge size and tree density, also taking into account factors like canopy coverage. These are our healthiest orchards, producing the highest yields, with the most uniformity. Lets not even start on fruit size, but that might just be Maluma :)


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