Mechanical Harvesting: What about Tree Health? Mechanical Harvesting: What about Tree Health? Jim Syvertsen and Juan C. Melgar 8 Dec 2009 Jim Syvertsen and Juan C. Melgar 8 Dec 2009 CREC

1. Leaf loss 2. Twig loss 3. Root exposure – trunk shaking 4. Bark loss “Barking” So, what’s the Problem ? Research studies using well-managed trees repeatedly mechanically harvested for 5 to 7 years: NO reductions in tree growth, yield or tree health for ‘Hamlin’, ‘Pineapple’, ‘Valencia’ & ‘Marsh ’ (Whitney, Burns, Syvertsen et al.)

FMC Trunk 4 Hz, 156 lbs. & 5” displacement 10 sec. & 20 sec. shake JKBU Films Inc. 10 % to 20 % Leaf loss

Leaf Loss ‘Hamlin’ Jan % 12% 12% (K-T Li et al. 2005) 2 %

How much leaf loss is too much? Fact is: Healthy Citrus trees: > leaves than req. for max. yield Defoliation up to 50 % of ‘Hamlin’ and ‘Valencia’ for 2 yrs No reduction in yield yet even at 50 % defoliation Photosynthesis of remaining leaves tends to increase Burns et al % Leaf Photosynthesis Defoliation P < Valencia

Root exposure after trunk shaking?  Drought stress?

‘Hamlin’ Harvest 7 Jan 2004 after 3 weeks drought Drought Stress: 9 Jan, 2 days post harvest irrigated and 0.34” rain on 9 Jan PM (K-T Li et al. 2005) Midday stem water potential (-MPa) Notharvested HandPicked10 Sshake20 Sshake Hand Har + drought 10 S + drought ns

Bark patch removal (pocket knife) Bark ?

Loss of flowers & fruitlets? ns ‘Valencia’ Harvest 20 Mar 2004 Drought Stress 1 day post harvest

% No change in yield (K-T Li et al. 2005) ‘Valencia’ Harvest 19 Mar 2004 (full bloom)

Excessive duration Leaf loss Flower loss Root damage Bark loss - Interactions with Drought Shake duration vs. fruit removal efficiency No negative effects on physiological or growth responses in well-managed ‘Hamlin’ and early season ‘Valencia’ Canopy shakers

Do Canopy Shakers Hurt Trees?

New scuffing Old

No changes in water status Old

Mechanical Harvesting in late-season ‘Valencia’ oranges ? Problem: Mechanical Harvesting in late-season ‘Valencia’ oranges ? Problem: -Mature and young fruit together - Young fruit are big enough to be removed with MH -Mature and young fruit together - Young fruit are big enough to be removed with MH

H o : Delay flowering by 2-3 weeks in March/April to have young fruits small enough not to be mechanically harvested in May / June

March 18 th 2009 (drought stressed trees) no flowers Winter drought stress: 100 days in 2007, 2008 & 2009 (Tyvek ® )

TYVEK COVERS ARE REMOVED IN MARCH IRRIGATION IS RESUMED FOR ALL TREATMENTS Covers off Irrigation resumed Drought stressed treatment Well irrigated treatment

March 18 th 2009 (well irrigated tree) No flowers in droughted trees Flowering and fruiting for next year’s crop? Flowering and fruiting for next year’s crop?

Prev. drought OPEN FLOWERS Irrigated trees began to flower Feb 13 th. Peak March 28 th Previous drought peaked Apr 12 th (2 weeks) Rain only Rain + irrigation All Irrig.19 th

FRUIT SET Number of green fruits is similar among treatments No effect on fruit yield next year Rain only Rain+irrigation Prev. drought Compensation  fruit set Rain only: best

OPEN FLOWERS Prev. drought stressed 13.4 (Leafy) Rain + irrigation 6.5 Rain only 6.5 LEAFY OR LEAFLESS INFLORESCENCES? (# of young leaves / open flowers) Drought-delayed treatment had a higher ratio of young leaves / open flower than the other treatments Compensation: Leafy shoots = greater yield

April 25 th 2008 (well irrigated tree)

April 25 th 2008 (previously drought stressed tree) With good water management: -Fruit size caught up -No yield loss

Water stress effects on this year’s crop?

- No effect of previous drought stress or harvest date - No effect on juice quality either ( o brix, % acid or brix/acidity) Fruit size (g) ns % juice : No effect on fruit quality 23 March 24 April

Prev. drought stressed trees Well irrigated trees Fruitlet loss (kg) Diam. (cm) 2.4 ± (1”) 13.9 ± (1 1 / 4 ”) Previously drought stressed Irrigated through winter After Mechanical Harvesting

Summary: Winter drought stress did not affect % juice or juice quality in the current crop ( ). CREC Winter drought stress delayed flowering but had no effect on fruit set of Valencia to be harvested late. Size caught up. No yield loss. No negative effects of MH on tree health or yield of healthy well-managed trees Less young fruit loss & increased harvesting efficiency in previously drought stressed trees than in well irrigated trees. Cover crops???

Mechanical Harvesting: What about Tree Health? Mechanical Harvesting: What about Tree Health? Jim Syvertsen and Juan C. Melgar 8 Dec 2009 Jim Syvertsen and Juan C. Melgar 8 Dec 2009 CREC