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Jonathan Dixon

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Avocados Australia

Avocado trees follow a predictable annual growth cycle. The cycle begins with root growth in winter, followed by flower induction in spring, flowering in late spring to early summer, fruit set and growth over summer, and another round of root growth in fall. Understanding an orchard's growth cycle allows growers to time management activities like fertilizer, fungicide, and pruning applications optimally throughout the year to balance tree growth, flowering, and fruit production. The growth cycle also influences alternate bearing and internal starch levels in avocado trees.

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Avocado Tree Growth Cycle Simon Newett Jonathan Dixon
This session ?What is a growth cycle? ?Why are growth cycles important? ?The dynamic nature of the growth cycle ?How you can use it as a powerful management tool ?Case studies ?Interactive discussion
Tree Growth Cycle (Phenology) ?Crop phenology is simply the seasonal change in growth that occurs over a reproductive cycle ?With tree crops it is an annual cycle ?Once identified it gives the opportunity to recognise competitive interactions between various components of the tree ?It can be developed and used as a management tool
Avocados Have A Predictable Annual Cycle ¡­ flowering ¡­fruit set ¡­fruit maturation ¡­shoot Dr. A.W. Whiley ¡­root growth growth
The Annual Cycle
The Annual Cycle
The Annual Cycle
The Annual Cycle BAY OF PLENTY, NEW ZEALAND F lo w e r b u d b r e a k F lo w e r R o o ts S p rin g le a f F lo w e r in d u c tio n / in itia tio n R o o ts F ru it g r o w th R o o ts S u m m er le a f F ru it d ro p S u m m e r le a f R o o ts F ru it d ro p JU N JU L AUG SE P OCT NOV DEC JA N FEB MAR APR M AY JUN
Why is the Avocado Tree Growth Cycle Important? ?Best timing of management activities oFertiliser, Phytophthora control, Water ?Gives an understanding of what may happen when there are problems e.g., Late hanging fruit can alter the flowering, growth flushes and starch in the tree ?Greater understanding of how the tree grows ?Lead to greater grower innovation in tree management
Photos of the same tree October 2007 and 2008
The Two Year Growth Cycle Why two years? ?The timing of phenological events can change from year to year ?The strength of the phenological event can also depend on what has happened in the previous year ?It is cumulative influences in the previous two years that determine the crop that is harvested
Flower Induction/Initiation on Spring flush Orchard Time Previous crop One April Regular Two early February Off year Three early March Off 2 years ?As much as six weeks difference between orchards ?Could affect timing of fertiliser and pruning Source: NZ Annual Research Report 2006
Three threads come together
Alternate Bearing Cycle
6 00 2 6/ 6 /0 00 10 5/2 6 /0 00 10 4/2 6 Tauranga Te Puna /0 00 10 3/2 6 /0 00 10 2/2 06 0 0/ 0 The Starch Cycle 1 1/2 5 Flowering /0 00 10 2/2 5 /1 00 10 1/2 5 /1 00 10 0/2 5 /1 00 10 9/2 5 /0 00 10 8/2 5 / 0 00 10 7/2 05 /0 0 10 6/2 5 /0 00 10 5/2 5 /0 00 10 4/2 5 /0 00 10 3/2 5 /0 00 10 2/2 5 0 0 Flowering 0/ 0 1 1/2 4 /0 00 10 2/2 4 /1 00 10 1/2 4 /1 00 10 0/2 4 /1 00 10 9/2 4 /0 00 10 8/2 4 /0 00 10 7/2 04 /0 0 10 6/2 4 /0 00 10 5/2 4 /0 00 10 4/2 /0 10 9 8 7 6 5 4 3 2 1 0 Average starch content (%)
Two year cycles with starch levels
Achieving The Right Balance ?Correct timing will help you achieve the optimum balance between:- ?leaf growth ¨C fruiting - root growth ?This balance will achieve:- ?good fruit set, but also . . . ?adequate leaf canopy (¡°the factory¡±) and root growth (¡°raw materials supply route¡±) to feed the fruit and set the tree up for the next year
The Concept Of The ¡°Sink¡± ?When part of the plant (e.g. fruit) is actively growing it acts as a ¡°sink¡± for resources such as sugars, water, minerals, chemicals . . . ?Whilst this part of the tree is the primary ¡°sink¡± it takes priority over other parts of the tree in attracting these resources
Some Management Practices Where Correct Timing In Relation To The Growth Cycle Is Critical . . . ?Water ? Nitrogen ?Phosphorous acid ? Minimal nitrogen (NZ?) ?Calcium ?Sunny? ? Boron ?Cincturing
Case Studies ?Timing of phosphorous acid ?Timing of calcium fertiliser ?Timing of SUNNY?
CORRECT TIMING OF PHOSPHOROUS ACID APPLICATION ?Refer to the growth cycle and look for when the roots are the primary ¡°sink¡± ?Roots are a strong ¡°sink¡± when there is little leaf, flowering or fruit development taking place ?Generally two opportunities per year, one is better than the other ?Other points to consider: ?Potential phytotoxicity of phosphorous acid to feeder roots ?MRLs in fruit
Critical application times for phosphorous acid for Phytophthora root rot control
Calcium Fertiliser Application For Optimising Fruit Content ?Refer to the growth cycle and look for when the fruit is the primary ¡°sink¡± ?Calcium is taken up via the water stream and distributed in the plant wherever water goes ?Fruit have stomata for about the first 6-8 weeks of their development, then they close up permanently forming the lenticels ?Whilst the stomata in the fruit are still open water moves through the fruit depositing calcium there ¨C this is therefore the most critical time for accumulating calcium in fruit
Uptake Of Calcium Into Fruit 8000 7000 6000 Fruit Ca (mg/kgdw) 5000 4000 3000 2000 1000 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Weeks after fruit set Source: Witney et al. (1990)
The Starch Cycle Critical time to have adequate calcium available in the soil solution
Correct Timing Of Sunny? For Improving Fruit Set And Size ?There is a fine balance at flowering time between resources being directed towards fruit set or leaf growth ?Excessive nitrogen in the plant at this time can swing the balance in favour of vegetative growth at the expense of fruit set ?Sunny? is a plant growth substance that suppresses shoot growth and swings the balance towards fruit set ?Refer to the growth cycle and consider the turning point for this resource allocation
FRUIT vs. SHOOT competition
FRUIT vs. SHOOT competition Sunny? Dr. A. W. Whiley
The Starch Cycle Critical time to apply Sunny? (when 50% of the flowers on the tree have opened and before more than 10% of the spring shoots have begun to grow)
The Starch Cycle When not to apply a HIGH dose of nitrogen
Grower Exercises 1 Where on the growth cycle would you pick as the most appropriate time(s) to apply the following:- ?Water ? Nitrogen ?Phosphorous acid ? Minimal nitrogen (NZ?) ?Calcium ? Boron ?Sunny? ?Cincturing
Grower Exercises 2 Based on your knowledge of the growth cycle what does it mean for the tree when:- ? There is a frost ¨C winter, over flowering? ? The fruit is hung late before harvest? ? There are changes in the timing of phenological events?
Acknowledgements
Jonathan Dixon

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Jonathan Dixon

  • 1. Avocado Tree Growth Cycle Simon Newett Jonathan Dixon
  • 2. This session ?What is a growth cycle? ?Why are growth cycles important? ?The dynamic nature of the growth cycle ?How you can use it as a powerful management tool ?Case studies ?Interactive discussion
  • 3. Tree Growth Cycle (Phenology) ?Crop phenology is simply the seasonal change in growth that occurs over a reproductive cycle ?With tree crops it is an annual cycle ?Once identified it gives the opportunity to recognise competitive interactions between various components of the tree ?It can be developed and used as a management tool
  • 4. Avocados Have A Predictable Annual Cycle ¡­ flowering ¡­fruit set ¡­fruit maturation ¡­shoot Dr. A.W. Whiley ¡­root growth growth
  • 8. The Annual Cycle BAY OF PLENTY, NEW ZEALAND F lo w e r b u d b r e a k F lo w e r R o o ts S p rin g le a f F lo w e r in d u c tio n / in itia tio n R o o ts F ru it g r o w th R o o ts S u m m er le a f F ru it d ro p S u m m e r le a f R o o ts F ru it d ro p JU N JU L AUG SE P OCT NOV DEC JA N FEB MAR APR M AY JUN
  • 9. Why is the Avocado Tree Growth Cycle Important? ?Best timing of management activities oFertiliser, Phytophthora control, Water ?Gives an understanding of what may happen when there are problems e.g., Late hanging fruit can alter the flowering, growth flushes and starch in the tree ?Greater understanding of how the tree grows ?Lead to greater grower innovation in tree management
  • 10. Photos of the same tree October 2007 and 2008
  • 11. The Two Year Growth Cycle Why two years? ?The timing of phenological events can change from year to year ?The strength of the phenological event can also depend on what has happened in the previous year ?It is cumulative influences in the previous two years that determine the crop that is harvested
  • 12. Flower Induction/Initiation on Spring flush Orchard Time Previous crop One April Regular Two early February Off year Three early March Off 2 years ?As much as six weeks difference between orchards ?Could affect timing of fertiliser and pruning Source: NZ Annual Research Report 2006
  • 13. Three threads come together
  • 15. 6 00 2 6/ 6 /0 00 10 5/2 6 /0 00 10 4/2 6 Tauranga Te Puna /0 00 10 3/2 6 /0 00 10 2/2 06 0 0/ 0 The Starch Cycle 1 1/2 5 Flowering /0 00 10 2/2 5 /1 00 10 1/2 5 /1 00 10 0/2 5 /1 00 10 9/2 5 /0 00 10 8/2 5 / 0 00 10 7/2 05 /0 0 10 6/2 5 /0 00 10 5/2 5 /0 00 10 4/2 5 /0 00 10 3/2 5 /0 00 10 2/2 5 0 0 Flowering 0/ 0 1 1/2 4 /0 00 10 2/2 4 /1 00 10 1/2 4 /1 00 10 0/2 4 /1 00 10 9/2 4 /0 00 10 8/2 4 /0 00 10 7/2 04 /0 0 10 6/2 4 /0 00 10 5/2 4 /0 00 10 4/2 /0 10 9 8 7 6 5 4 3 2 1 0 Average starch content (%)
  • 16. Two year cycles with starch levels
  • 17. Achieving The Right Balance ?Correct timing will help you achieve the optimum balance between:- ?leaf growth ¨C fruiting - root growth ?This balance will achieve:- ?good fruit set, but also . . . ?adequate leaf canopy (¡°the factory¡±) and root growth (¡°raw materials supply route¡±) to feed the fruit and set the tree up for the next year
  • 18. The Concept Of The ¡°Sink¡± ?When part of the plant (e.g. fruit) is actively growing it acts as a ¡°sink¡± for resources such as sugars, water, minerals, chemicals . . . ?Whilst this part of the tree is the primary ¡°sink¡± it takes priority over other parts of the tree in attracting these resources
  • 19. Some Management Practices Where Correct Timing In Relation To The Growth Cycle Is Critical . . . ?Water ? Nitrogen ?Phosphorous acid ? Minimal nitrogen (NZ?) ?Calcium ?Sunny? ? Boron ?Cincturing
  • 20. Case Studies ?Timing of phosphorous acid ?Timing of calcium fertiliser ?Timing of SUNNY?
  • 21. CORRECT TIMING OF PHOSPHOROUS ACID APPLICATION ?Refer to the growth cycle and look for when the roots are the primary ¡°sink¡± ?Roots are a strong ¡°sink¡± when there is little leaf, flowering or fruit development taking place ?Generally two opportunities per year, one is better than the other ?Other points to consider: ?Potential phytotoxicity of phosphorous acid to feeder roots ?MRLs in fruit
  • 22. Critical application times for phosphorous acid for Phytophthora root rot control
  • 23. Calcium Fertiliser Application For Optimising Fruit Content ?Refer to the growth cycle and look for when the fruit is the primary ¡°sink¡± ?Calcium is taken up via the water stream and distributed in the plant wherever water goes ?Fruit have stomata for about the first 6-8 weeks of their development, then they close up permanently forming the lenticels ?Whilst the stomata in the fruit are still open water moves through the fruit depositing calcium there ¨C this is therefore the most critical time for accumulating calcium in fruit
  • 24. Uptake Of Calcium Into Fruit 8000 7000 6000 Fruit Ca (mg/kgdw) 5000 4000 3000 2000 1000 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Weeks after fruit set Source: Witney et al. (1990)
  • 25. The Starch Cycle Critical time to have adequate calcium available in the soil solution
  • 26. Correct Timing Of Sunny? For Improving Fruit Set And Size ?There is a fine balance at flowering time between resources being directed towards fruit set or leaf growth ?Excessive nitrogen in the plant at this time can swing the balance in favour of vegetative growth at the expense of fruit set ?Sunny? is a plant growth substance that suppresses shoot growth and swings the balance towards fruit set ?Refer to the growth cycle and consider the turning point for this resource allocation
  • 27. FRUIT vs. SHOOT competition
  • 28. FRUIT vs. SHOOT competition Sunny? Dr. A. W. Whiley
  • 29. The Starch Cycle Critical time to apply Sunny? (when 50% of the flowers on the tree have opened and before more than 10% of the spring shoots have begun to grow)
  • 30. The Starch Cycle When not to apply a HIGH dose of nitrogen
  • 31. Grower Exercises 1 Where on the growth cycle would you pick as the most appropriate time(s) to apply the following:- ?Water ? Nitrogen ?Phosphorous acid ? Minimal nitrogen (NZ?) ?Calcium ? Boron ?Sunny? ?Cincturing
  • 32. Grower Exercises 2 Based on your knowledge of the growth cycle what does it mean for the tree when:- ? There is a frost ¨C winter, over flowering? ? The fruit is hung late before harvest? ? There are changes in the timing of phenological events?