Transcript What about Tree Health? – Jim Syvertsen (Dec. 2009)

Mechanical Harvesting:
What about Tree Health?
Jim Syvertsen and Juan C. Melgar
8 Dec 2009
CREC
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.)
So, what’s the Problem ?
1. Leaf loss
2. Twig loss
3. Root exposure – trunk shaking
4. Bark loss “Barking”
FMC Trunk shaker
@ 4 Hz, 156 lbs. & 5” displacement
10 sec. & 20 sec. shake
10 % to 20 % Leaf loss
JKBU Films Inc.
Leaf Loss
‘Hamlin’ Jan 2004
% leaf removal
20.0
11%
12%
12%
10 S
10 S +
drought
20 S
15.0
10.0
5.0
2%
0.0
Hand
(K-T Li et al. 2005)
Hand +
drought
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
Burns et al. 2001-03
Leaf Photosynthesis
16
y = 0.0599x + 8.4388
R2 = 0.1803
14
P < 0.05
12
10
8
2003 Valencia
`
6
4
2
0
0
12
25
Defoliation
50 %
Photosynthesis of remaining leaves tends to increase
Root exposure after
trunk shaking?
I Drought stress?
Midday stem water potential (-MPa)
‘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
2.0
1.8
9-Jan
1/ 9 d
1/ 12d
bc
1.6
1.4
12-Jan
a
a
c
c
ab
1.2
ns
1.0
0.8
0.6
0.4
0.2
0.0
Not
harvested
Hand
Picked
10 S
shake
20 S
shake
Hand Har
10 S
+ drought + drought
(K-T Li et al. 2005)
Bark ?
Bark patch removal (pocket knife)
Mid-day stem water potential (-MPa)
‘Valencia’ Harvest 20 Mar 2004
Drought Stress 1 day post harvest
1
ns
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Unharvest
Hand
10 S
10 S + Bark
removal
20 S
Loss of flowers & fruitlets?
Flr. & yng. frt. removal (%)
‘Valencia’ Harvest 19 Mar 2004 (full
bloom)
16
14
12
10
8
6
4
2
0
12- 13 %
Hand
10 S
20 S
No change in yield
(K-T Li et al. 2005)
Shake duration vs. fruit removal efficiency
Excessive duration Leaf loss
Flower loss
Root damage Bark loss
- Interactions with Drought
No negative effects on physiological
or growth responses in well-managed
‘Hamlin’ and early season ‘Valencia’
Canopy shakers
Do Canopy Shakers
Hurt Trees?
Old
New scuffing
Old
No changes
in water status
Mechanical Harvesting in late-season
‘Valencia’ oranges
? Problem:
- Mature and young fruit together
- Young fruit are big enough to be removed
with MH
Ho:
Delay flowering by 2-3 weeks in March/April
to have young fruits small enough not to be
mechanically harvested in May / June
Winter drought stress:
100 days in 2007, 2008 & 2009
(Tyvek®)
March 18th 2009 (drought stressed trees)
no flowers
TYVEK COVERS ARE REMOVED IN MARCH
IRRIGATION IS RESUMED FOR ALL TREATMENTS
Stem water potential (-MPa)
4.0
Covers off
Irrigation resumed
3.5
3.0
Drought stressed treatment
2.5
2.0
1.5
1.0
Well irrigated treatment
0.5
0.0
Jan
Feb
Mar
Apr
March 18th 2009 (well irrigated tree)
No flowers in droughted trees
Flowering and fruiting
for next year’s crop?
35
3500
30
3000
Rain only
25
2500
Rain + irrigation
20
2000
15
1500
10
All
Irrig.19th
5
1000
Prev. drought
Open flowers / tree
Open flowers / 30 shoots / tree
OPEN FLOWERS
500
0
0
Feb
13th
Feb
28th
Mar
13th
Mar
28th
Apr
12th
Apr
30th
May
18th
June
13th
Irrigated trees began to flower Feb 13th. Peak March 28th
Previous drought peaked Apr 12th (2 weeks)
FRUIT SET
GREEN FRUITS
Rain only: best
18
2000
1750
16
1500
14
12
1250
Rain only
Rain+irrigation
Prev. drought
10
8
1000
750
Compensation
h fruit set
6
4
500
2
250
0
0
Feb
13th
Feb
28th
Mar
13th
Mar
28th
Apr
12th
Apr
30th
May
18th
June
13th
Number of green fruits is similar among treatments
No effect on fruit yield next year
Green fruits / tree
Green fruits / 30 shoots / tree
20
OPEN FLOWERS
LEAFY OR LEAFLESS INFLORESCENCES?
(# of young leaves / open flowers)
Rain + irrigation
6.5
Rain only
6.5
Prev. drought stressed 13.4
(Leafy)
Drought-delayed treatment had a higher ratio of
young leaves / open flower than the other treatments
Compensation: Leafy shoots = greater yield
April 25th 2008
(well irrigated tree)
April 25th 2008 (previously
drought stressed tree)
With good water management:
-Fruit size caught up
-No yield loss
Water stress effects
on this year’s crop?
2007-09: No effect on fruit quality
250.0
23 March
24 April
% juice
Fruit size (g)
200.0
150.0
100.0
50.0
0.0
% Juice
Irrigation
Avg Frt Size
Drought
Irrigation
ns
ns
Drought
- No effect of previous drought stress or harvest date
- No effect on juice quality either (obrix, % acid or brix/acidity)
Irrigated through winter
After
Mechanical
Harvesting
Previously drought stressed
Prev.
drought
stressed
trees
Well irrigated
trees
Fruitlet
loss (kg)
2.4 ± 0.4
13.9 ± 4.5
Diam. (cm)
2.55 (1”)
3.15 (1 1/4”)
Summary:
No negative effects of MH on tree health or yield
of healthy well-managed trees
Winter drought stress delayed flowering but had
no effect on fruit set of Valencia to be harvested
late. Size caught up. No yield loss.
Winter drought stress did not affect % juice or
juice quality in the current crop (2007-2009).
Less young fruit loss & increased harvesting
efficiency in previously drought stressed trees
than in well irrigated trees.
Cover crops???
CREC
Mechanical Harvesting:
What about Tree Health?
Jim Syvertsen and Juan C. Melgar
8 Dec 2009
CREC