4th

NQ AVOCADO STUDY GROUP Minutes from meeting at David Adil‟s orchard Mareeba

9:00 am till 2:30 pm Tue 28 April 2009

Aim of project

“Make Australian avocado production more internationally competitive”

Main topic of today

“Nutrition”

Take home messages

First fix Phytophthora root rot

No roots (because of poor Phytophthora control) = poor nutrition

Poor irrigation management = poor nutrition

Unless you are monitoring your leaf and soil nutrition you are just guessing - and probably

wasting money

Regular leaf & soil analyses build a nutrition history for your farm & every farm is different

A little bit often for nutrient applications is usually best

Tailor your nutrition to tree growth stages (phenology cycle)

There is little evidence to show that foliar nutrition works, except boron at flowering (uptake

by flowers not leaves), and it confounds leaf analyses.

Take particular care with boron fertilising – there is a narrow window between deficiency

and toxicity

PROGRAM

MORNING TEA

Welcome and introduction – Matt Weinert

Avocado nutrition & fertigation and the close link between irrigation & nutrition –

Graeme Thomas, GLT Consulting

Avocado nutrition overview – Simon Newett

Case study of fertiliser recommendations based on a soil and leaf analysis – Graeme

Phosphorous acid monitoring & possible trial – Graeme Thomas

BBQ LUNCH

Overview of orchard and farm walk – David Adil

Decide on topic and date for next avocado workshop, complete evaluation sheets

David Adil discussing a point with Graeme Thomas during the

farm walk

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Present (50+3)

Janelle & David Adil, Nathan & Dwayne Ashford (P & C Howe), Jackie Atkinson, Eric &

Tracey Battistin, M. Battistin, Ron Blundell, Susan Christensen, Mick Coleman (G, E & L

Masasso), Mick Coles, Sam & Kylie Collins, Yan Diczbalis, William Ericson, Dino Falvo,

Colin & Nathan Foyster, Ian Gardner, Chelley Howe, Peter Holt, KW & SP Hunt Farming,

Andrew Irving, Damien Kohlman, Dell & Don Lavers, Ian & Ann Leighton, Wes Marks,

Warren Mulla, Remzi Mulla, Frank Munoz, Aaron Myrteza, Matthew Perkes, Giovanni

Ravanello, Tony Salmon, Ron Schweitzer, Gerry De Speville, Doug Stuart, Mario Tessar,

Theart Farming, Mark Toohey, Clare Visin (Kamai P/L), Karl Ward, Bob Waterman, Ted

Winston, Leonie Wittenberg, Michael Zappala, Walter Zugno

Simon Newett & Matt Weinert Qld PIF), Graeme Thomas (GLT Horticultural Services P/L)

'Whilst every care has been taken in preparing these minutes, Queensland PIF accepts no responsibility for decisions or actions taken as a result of any data, information, statement or advice, expressed or implied, contained in these minutes. The views and recommendations of the speakers are not

necessarily endorsed or supported by Queensland PIF"

Note: there wasn‟t time on the day to present all the information intended but a copy of all MS Powerpoints presentations (those covered on the day and those not) are included with

these minutes, they include photographs of avocado nutrient deficiency symptoms.

AVOCADO NUTRITION

Graeme Thomas, GLT Consulting and Simon Newett, Queensland PIF, Nambour

Here are some additional notes covering the discussion and questions that arose.

Phytophthora root rot Graeme began by pointing out the importance of first controlling Phytophthora root rot -

without a decent feeder root system the trees can‟t take up water or nutrients!

Phytophthora can demolish a perfectly healthy root system within only 3 weeks!

Last week on the Sunshine Coast, which has had some very wet spells this year, very few

feeder roots could be found. This particular farm recorded a root phosphorous acid level of

40ppm in November last year (above the recommended minimum level of 25ppm) but it is

expected to have dropped to about 15ppm by February therefore giving no protection. This

is a serious position to be in and given that another very wet spell has just been experienced

(late May) in that area the outlook for the health of the trees (and of course next year‟s crop) is not good.

Graeme‟s next point was that you need to pay attention to detail in managing your orchard.

Use of manures Manures can vary greatly in their analysis. Always make sure you obtain a nutritional

analysis for manure before you purchase it and factor the nutrition applied via manures into

your annual nutrition program. One of the dangers of using manures is that nutrients can be

released at unpredictable times, a large release of nitrogen at the wrong time of year can

affect crop set and fruit quality. Another danger is that manures can contain a lot of chloride

Please also refer to copies of MS PowerPoint presentations attached.

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and/or sodium, these two elements are very available to plants and toxic to avocados, hence

the importance of getting an analysis.

Manganese toxicity Manganese can be toxic and sometimes there will be a band of high manganese soil that runs

through a district. High manganese is often found in red volcanic soils. The amount of

manganese in the soil solution increases as the soil pH drops and as conditions get wetter.

Thus in soils inherently high in manganese a soil pH of 6.5 (instead of the usual 5.5) is

recommended.

Effect of temperature on nutrient availability Nutrients are less available at lower soil temperatures. Zinc is a good example of this.

Boron Boron must be applied to the soil. Foliar boron sprays are only a stop gap measure to be used

at flowering time if your leaf tissue levels are already deficient. Dr Tim Smith‟s research

showed that an application of foliar boron only generated a response if the leaf tissue boron

level was already deficient (below 30ppm). Foliar applied boron is taken up by the flowers

and not the leaf. However treat boron applications with care – there is a very narrow window

between boron being deficient and toxic especially on lighter soil types. Seek expert advice

on boron rates; your soil texture has a major bearing on the rates required. The AVOMAN

software gives a customised boron application based on many factors. Boron leaches easily

from the soil so little and often is the key.

Leaf nutrient tissue testing The timing of leaf sampling for analysis is critical in order to make sense of your results.

The recommended time is autumn (April/May) when the summer leaf flush leaves are fully

grown and hardened. This is the time of year when nutrient levels in the leaf are the most

stable (leaf growth has finished and flower bud break and flowering have not commenced).

The optimum levels were established for this time of year. Refer to the pictures of the

growth cycles given below for timing of these events.

There is another time of year when a check is sometimes done – this is when the spring leaf

flush has matured (about Nov/Dec), (Andrew Irving of Howe farming said that Oct was the

time on his orchard). Optimum levels have not been established for this time of the year but

the optimum levels for autumn are used as a guide.

Sample a minimum of 40 leaves and pick them from across the block and from all sides of

the tree. A zigzag pattern should be followed across the block or as Graeme put it “wander like a drunken sailor” across the block.

Question: Can you sample young trees? Response: Yes but be aware that optimum leaf levels in young trees are different from mature trees, especially nitrogen which is a lot higher.

Question: What about sap testing? Response: Sap analysis in tree crops is unreliable. Sap nutrient levels can vary enormously from one day to another especially following rainfall or irrigation. Leaf tissue tests on the other hand tell a story of what has happened over the previous few months.

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Question: When sampling on sandy soils should you sample deeper? Response: Not necessarily because 80% of the feeder roots will still be in the top 8” of soil so this is the area roots source nutrients from and the area you should be most interested in. Deep sampling is sometimes done to provide more information if a problem occurs – in some situations subsoils can be very acid or may contain toxic levels of a nutrient.

Gypsum Gypsum is a mild fungicide (against Phytophthora root rot) as well as being a source of

calcium. Regular light applications are beneficial but monitor via calcium levels in the soil

regularly to ensure it is kept in balance with other nutrients.

Question: How often should you soil sample? Response: On heavier soils every 3 years is usually enough whilst on sandy soils every two years is recommended. Andrew Irving from Howe farming samples annually.

There is a danger in poor soils that during very wet conditions nutrients from deeper levels

will be brought to the surface layers but avocados should not be grown in these soils anyway.

Question: Which is best – boric acid or solubor? Response: Not a great deal of difference but boric acid seems to give a better response in heavier soils, also solubor changes into boric acid in the soil anyway.

Question: How effective is zinc sulphate heptahydrate compared with zinc chelate? Response: Proper trials are needed to compare these two and different responses may be received in different soils, however in most cases zinc sulphate heptahydrate works quite adequately and is cheaper. Question: What about liquid calcium fertilisers? Response: Probably OK (applied to the soil) but they can be expensive. A waste of time applying as a foliar spray. Question: Is humic acid effective? Response: Gerry de Speyville (Agrichem) said that there were responses on sandy soils but not on clay soils.

Nitrogen If nitrogen levels are too high they give rise to poor quality fruit (high nitrogen results in low

fruit calcium). In terms of the timing of nitrogen, small amounts throughout the year with a

greater proportion in autumn and a lower proportion through winter seem to be giving good

results. Large applications around the flowering, fruit set and early fruit growth period will

promote leaf growth at the expense of fruit set, retention and quality.

Importance of the first 6 weeks after fruit set During this period the trees must be “singing”. This is the time when fruit size is determined and also the time when fruit calcium content (and therefore quality) is determined. If there is

any moisture stress through this period then fruit will be smaller. If there is insufficient

available calcium in the soil lat this time and/or moisture stress occurs then fruit calcium

levels will be low giving the fruit a shorter shelf life and making them more prone to rots.

Rootstocks Follow the results of the rootstock trial in NQ. Note: there are different sources of Velvick

rootstock seed; the best are from Velvick trees that are isolated from other varieties and

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therefore are self pollinated producing seed that are more true to type. Others close to other

varieties get cross pollinated so the seed is more variable and not as good.

Shepard There was general acknowledgement that the Shepard variety generally behaves quite

differently especially in terms of its timing compared with Hass and NQ growers would

benefit from a closer look and study of the phenology of this variety. Refer to growth cycles

below.

Monitoring phosphorous acid levels in roots

A test is available that allows you to monitor the level of phosphorous acid in feeder roots

and thus help you make treatment decisions. It is desirable to have a phosphorous acid level

in the feeder roots of over 25ppm to stop Phytophthora growth but less than 150ppm which

inhibits root growth.

For foliar sprays the pH of the solution should be between 7 and 7.5. At pHs below this (i.e.

acid) you risk phytotoxicity which is brought about by the acidity of the spray releasing

copper from residues of fungicide sprays on the leaves. If too much copper is released it

causes leaf burn.

Phytophthora root rot update Timing of phosphorous acid applications

Timing is critical in order to maximise the amount of phosphorous acid that you get into the

feeder roots and to minimise the amount that finds its way to the fruit. Based on the principle

that when you apply it the material will go to that part of the tree that is actively growing

(known as the “sink”) you need to follow the growth cycle and time the application to

coincide with when root growth is taking place and other parts of the tree are not growing.

From top: Growth cycles for Shepard in Mareeba, Hass in Mareeba, and Hass in Walkamin. The observations to construct these growth cycles were collected as part of the AVOMAN

project in the 1980s.

flower bud break

flower

leaf flush

fruit thinning

root growth

suggested times to apply

phosphorous acid

The amount of feeder roots you require for a sample is what will fit in the circle formed between touching the tip of your thumb and index finger (thus more feeder roots are required than shown in this photo). Testing kits are available from: SGS Agritech, PO Box 549, 214 McDougall St, TOOWOOMBA QLD 4350

Phone: 46 33 0599, Fax: 46 33 0711 Email au.agritech.twb@sgs.com

A test including GST and recommendations costs $92.40

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Since phosphorous acid can be slightly toxic to roots above about 150 ppm, it is

recommended that it be applied slightly after the peak of root growth and when no other

significant growth is taking place in the tree. Based on this theory the two windows of

opportunity (to apply phosphorous acid) in the growth cycles shown above are in May/June

and again in early December (as indicated by the blue arrows).

Graeme has found that if we achieve high root phosphorous acid levels in spring then

adequate levels generally persist till the following autumn.

Foliar sprays Ensure high spray volumes are used – 2,500 to 3,000 L/ha for large trees.

Don‟t add wetting agents as these sometimes lead to leaf burn.

Bark painting Trials with bark painting on older trees are not giving consistent results, but it appears to be

more effective on young trees. Gerry de Speyville says however that Agrichem is likely to

go ahead with registration of the penetrant used with phosphorous acid in bark painting.

Graeme said there is a risk of chemical cincturing of the tree if the wrong rate of

phosphorous acid or penetrant is used.

Question: How long should you wait after treatment with phosphorous acid before taking a root sample? Response: About 2 to 3 weeks.

Suggested research project for NQ

A trial needs to be done in NQ especially on the Shepard variety where monthly applications

of phosphorous acid are applied then tested for whilst also noting the stage of the growth

cycle. Once the mango conference is over ATAGA plans to call a meeting to plan the

funding and requirements of this research. Agrichem offered to assist also.

FARM WALK - David Adil

David started growing avocados here 13 years ago. He lost some trees on the poorer soils

and has since moved onto the better soils. Two very wet spells have affected his orchard,

one in February 2008 when 26” fell in 28 days and in January/February this year when 26” fell at an average rate of 1” per day. He has lost 100 trees and has another 100 that he describes as sick.

Chronic boron deficiency a year or two ago caused what he calls “scabby branch”:

Chronic boron deficiency a couple of years ago caused this scaly bark

symptom that which David calls “scabby branch”

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Don‟t have the sprinkler too close to the tree trunk because it over waters the side of the trunk it is closest too and creates a dry „water shadow‟ on the other side.

Graeme described the practice of cincturing branches. Branches are cinctured in autumn (no

more than one quarter of the branches in the tree) and these branches can be the ones

removed if you are using „selective limb removal‟ as a canopy management practice after the

fruit is harvest from that branch about 12 months later.

Damage from ectropis loopers (above) & the well camouflaged moths on the avocado tree trunk (right, heads individually

arrowed) that lay the eggs that hatch into these loopers

A symptom of stress (especially moisture stress) is incomplete abscission of the fruit stem (red arrow left), this symptom is called ‘ringneck’. Ringneck can lead to a dead (dark brown) seed coat (above right) which results in a smaller fruit. Compare this with the larger fruit (to its left) that has a live (light ochre colour) seed coat. Stress causes premature death of the seed coat. The hormones that make the fruit grow are made in the seed coat so if the seed coat dies the fruit stops growing.

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ACKNOWLEDGEMENTS

Very many thanks to David Adil and family for hosting the meeting and to Graeme Thomas

(GLT Horticultural Services P/L) for travelling to FNQ to present at the meeting.

NEXT MEETING

Topic: Phytophthora cinnamomi root rot management

When: About Sep 09

Venue: To be advised

Topics suggested

Topic Votes

Phytophthora root rot control 26

More about „Shepard‟ and its management FNQ 12

Phenology (growth cycles) 11

Rootstocks 9

Canopy management 8

APPENDICES & ATTACHMENTS

Grower feedback from the meeting

MS PowerPoint “Avocado nutrition” - Graeme Thomas

MS PowerPoint “Fertigation principles” - Graeme Thomas

MS PowerPoint “Avocado nutrition overview‟ - Simon Newett

MS PowerPoint “Avocado nutrient deficiency/toxicity symptoms” - Simon Newett

MS PowerPoint “Different fertilisers” - Simon Newett

Simon Newett

Queensland DPI&F

PO Box 5083 SCMC

NAMBOUR QLD 4560

Email: simon.newett@dpi.qld.gov.au

Phone: 54 449 619

Fax: 54 412 235

Matt Weinert

Queensland DPI&F

PO Box 1054

MAREEBA QLD 4880

Email: matthew.weinert@dpi.qld.gov.au

Phone: 4048 4651

Fax: 4092 3593

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AVOMAN APPLICATIONS FOR AVOCADO NUTRITION MANAGEMENT

The AVOMAN avocado management software includes several features that support

nutrition management:

Illustrated Help files (see some of the topics listed below)

Customised nutrient requirements based on integrating leaf and soil results, soil

texture, local crop phenology, variety, rootstock, recent conditions etc

Record keeping and reporting for fertiliser applications

Record keeping, reporting and graphing soil & leaf analyses

A jobs „browser‟ which can be used to quickly find information from your records, e.g. your last boron application

Lists of some of the nutrition topics for which there is

comprehensive information in the AVOMAN help files

Window in AVOMAN where AVOMAN‟s tailored nutrient recommendations are displayed to convert into rates of chosen fertilisers

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Example of a fertiliser report listing the applications required for the season. These recommendations were generated by AVOMAN.

Example of a leaf analysis chart showing leaf nitrogen levels over five seasons

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Example that shows how the Jobs & reminders browser is used to zero in on records of boron

applications to „Bundaberg Hass‟ block and identify when the last application was made

A fertiliser report that summarises the amounts of fertilisers required for the season for the block

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RESULTS FOR FEEDBACK SHEET

North Queensland (Avocado Nutrition 28/04/09)

Your current farm practice:

1. Do you have a regular and effective root rot prevention and control program? YES 10 NO 4

2. How often do you get leaf analysis done? (Please circle the most appropriate answer)

EVERY YEAR 9 EVERY 2ND YEAR 1 DON‟T DO ONE 3 (EVERY 6-8 WEEKS 1)

3. How often do you get soil analysis (including pH) done?

EVERY 1-2 YEARS 11 EVERY 3-5 YEARS 3 DON‟T DO ONE

4. How do you decide your fertiliser rates and program? (tick the box(es) that apply)

I decide the program on my own …………………… 4

I use the services of a consultant……….................. 11

With the assistance of a DPI&F officer…………….. 0

I use AVOMAN to help make decisions…………..… 0

My fertiliser rep makes the recommendations……... 3

5. How many times per year do you apply boron? Not sure, 1, 4, 5-7, 5-7, 7, 8-10, 10, 10-12, 12, monthly, 20, „often‟, „however many is

recommended by Graeme‟

6. If you fertigate, how often do you check the uniformity and output of your irrigation system?

EVERY 6 MONTHS EVERY YEAR 8 LESS THAN ONCE PER YEAR 2 N/A 3

7. Do you actively work to increase or maintain your organic matter levels, e.g. by mulching? YES 12 NO

Today‟s workshop:

1. How useful did you find this workshop? Please circle the most appropriate description.

NOT USEFUL FAIRLY USEFUL USEFUL 5 VERY USEFUL 7 EXTREMELY USEFUL 3

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2. List the 3 most useful things that we did today and why?

Phytophthora info, tissue sampling, irrigation changes ie sprinkler location.

Graeme Thomas spoke, Graeme Thomas spoke again, Simon Newett.

Plant nutrition, phosphoric acid foliar spraying, Phytophthora.

Fertiliser program fine tuning, fine tune phytophthora.

Put emphasis on major nutrients & explained importance, spoke about not applying

if not required, Timing! – Importance of, leaf testing.

Nutrition explanation, rootrot / phytophthora control, orchard walk

Orchard walk – view trees, Graeme Thomas – knowledge.

Farm walk

Nutrition, root rot.

Nit fertiliser, control & when phytophthora rot

3. Did you feel able to participate? (Please circle the most appropriate description) NO 1 A LITTLE SOME 5 MANY CHANCES 4 EVERY CHANCE 5

4. Have you established new contacts today and/or had beneficial discussions with others? YES 12 NO 2

5. Have you learnt something new about avocado production and/or fruit quality today? YES 14 NO 1

6. Has what you learnt today made you question your current farm practices? YES 14 NO 0

7. Do you think, from what you learnt today, you will make a change to your farm practice? YES 13 NO 1

If yes briefly describe:

Watch out and follow (try to), phenology. Must organise orchard into current irrigation blocks before next leaf samples. Application (N.P.K) Analyse leaf test more, record & plan applications better. Application of nitrogen. Adjust nutrition. Maybe – need more resource into outcomes, especially on Shepard avo‟s. More control phytophthora for root health. Concentrate on & analyse soil/leaf reports.

8. In running the day, what could we do better?

More time (too rushed)

Keep on time

Key speakers should stay longer

Have Graeme & Simon here longer

Very well run

More lunch

Key speakers need to be around a bit longer so we can speak to them a bit more.

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9. Any other comments:

Need to keep on time – invitation 9am start Editors note: these meetings are always designed to start with smoko at the advertised time for several reasons - to enable late comers to arrive without disrupting proceedings (particularly out of respect for special invited speakers and other growers who are trying to listen), allow growers to have a cuppa, relax a bit and to catch up („network‟) with others so that 30 mins later they are ready to give their full attention to invited speakers when they start – this approach we believe is working very well – however in future we will specify on the invitations that the meetings commence with smoko.

More work to be done in different FNQ growing areas. Hass have huge difference

between Malanda/Atherton/Walkamin. Flush times different. When to inject? How

big is the window?

Less comment from salesmen.

Where were the fennel sausages?? Slipping Matt!

More work looking into Shepard variety rather than Hass or other varieties we don‟t grow.

Minutes of last meeting

1. Did you receive minutes of the last meeting? YES 10 NO 3

2. Did you read them? YES 10 NO

3. What did you like about them?

Help remember about the meeting

Clarity

Good for reference

Good to read and refresh the mind with same things over and over.

4. Any suggestions to improve them?

No

Finish at 6pm for drinks (beer) can be supplied by TGT & Elders &

Landmark!