syvertson yield

							Effects of Mechanical harvesting on
    Tree Health and Yield



      Kuo-Tan Li
      Jim Syvertsen

      UF, IFAS
      Citrus Research & Education Center
      Lake Alfred
                                  6 Apr 2006
? Compensation for defoliation
  M H and abscission chemicals? 20% def.
No yield reduction even at 50 % def.
                      for 2 years (Yuan et al. 2005)
                                        ‘Valencia’ May 2003
          Leaf Photosynthesis

                                16
                                                y = 0.0599x + 8.4388
                                14                   R2 = 0.1803

                                12                   P < 0.05
                                10

                                8

                                6

                                4

                                2

                                0
                                     0 12 25        50 %
                                        % Defoliation                  (G-Sanchez
                                                                           et al. 2003)
Defoliation – Light Interception
       Avg. 10 to 12%
       leaf area
                                                                              Pre-harvest
       removed                                                                Post-harvest
                                                          100




                           Total light interception (%)
                                                           90
       No affect on leaf
                                                          80
       photosynthesis                                     70
                                                          60
       No affect on                                       50
       canopy light                                       40
       interception or                                    30
                                                          20
       leaf area next
                                                          10
       year                                                0
                                                                Hand   10 S        20 S
Flower Loss: Nodes?

      Avg. 10 to 12%                              50                        2004
      leaf area removed                           45
                                                                            2005

                                                  40
      Does not affect leaf




                             Flowering node (%)
                                                  35
      photosynthesis                              30
                                                  25
      No affect on canopy                         20
      light interception,                         15
      leaf area, or return                        10
      bloom next year                              5
                                                   0
                                                       Hand   10 S   30 S
Petal fall –Flower loss
      10 to 15%
      fruitlets
                                           25                        2004
      removed when
                                                                     2005
      harvested at
      bloom                                20




                      Flower removal (%)
      Does not                             15
      reduce final
      fruit set                            10


      Does not                             5
      reduce next
      crop yield or                        0
      fruit size                                Hand   10 S   20 S
Petal fall -- Yield

      10 to 15% fruitlet                                                2004
      removed at bloom                       100                        2005
                                             90
      Does not reduce                        80




                           Yield (kg/tree)
      final fruit set                        70
                                             60

      Does not reduce                        50
                                             40
      next crop yield or
                                             30
      fruit size
                                             20
                                             10
                                               0
                                                   Hand   10 S   20 S
Effect of Mechanical harvesting on
Tree Health and Yield
What do we know about
mechanical harvesting on   No long term
                           effect on ‘Hamlin’
citrus tree health and     yield (7- 8 years)
yield?
                           Yield Reduction
                           in ‘Valencia’
                           when harvested
                           late with or
                           aggressive trunk
                           shaking


                               Whitney et al.,
Problem: Visible
Physical injuries to trees
occur during
mechanical harvesting:



         Defoliation

         Petal fall

         Bark scuffing

         Root exposure
Defoliation
        Avg. 12 to 13%
        leaf area removed
                                                                           2004
                                                 18                        2005
        No affect on leaf
                                                 16
        photosynthesis
                                                 14




                               Defoliation (%)
                                                 12
        Does not affect
                                                 10
        canopy light
                                                  8
        interception or leaf
                                                  6
        area next year
                                                  4
                                                  2
                                                  0
                                                      Hand   10 S   20 S
Effect of Mechanical harvesting on
Tree Health and Yield
Physical injuries occur
    during mechanical
          harvesting:
       Defoliation

       Petal fall

       Bark scuffing
       Twig breakage

       Root exposure
Bark scuffing
      Replaced with
      new bark
      tissue within a
      year

      Does not
      reduce growth
      increment

      No increased
      disease
      infections or
      pest invasions
Physical injuries
    during mechanical
          harvesting:

      Defoliation

      Petal fall

      Bark scuffing, Twig loss

      Root exposure
         Root death
           Water Relations?
Root exposure – Drought stress
       Little effect on
                                         ‘Hamlin’ after 2 weeks of drought
       root water and                                    2.0                                               0.3” rain
       nutrient uptake,                                  1.8




                          Mid-day stem water potential
       exc. excessive                                    1.6
       shaking and




                          Midday Drought stress
                                                         1.4
       drought                                           1.2




                                    (-MPa)
                                                         1.0

       Little effect on                                  0.8
                                                         0.6
       fine root growth
                                                         0.4
                                                         0.2
                                                         0.0




                                                                                                Hand + Drought

                                                                                                                 10 S + Drought
                                                               Unharvest




                                                                                         20 S
                                                                                  10 S
                                                                           Hand
Root exposure
      Little effect on
      root water and
      nutrient uptake,
      exc. excessive
      shaking and
      drought

      Little effect on
      fine root growth
Root periscope




                 (K-T Li et al., 2005)
                Video of Repeated
                   measurements




Root growth
 through time
Effect of Mechanical harvesting on
Tree Health and Yield
                                                    300
Summary
                                                    250
      Annual variation in yield




                                  Yield (kg/tree)
      is not related to harvest
      methods                                       200                  2004
      Visible Injuries by                           150
      mechanical harvesting
      are relatively mild and                       100
      do not affect tree health                                2005      Hand
      and return yield                               50                  10S
                                                                         20S
                                                     0
                                                          0   1000    2000      3000

                                                              Fruit / tree
Effect of Mechanical harvesting on
Tree Health and Yield
Exception
       Harvesting
       ‘Valencia’ after
       May can remove
       young fruit and
       reduce yield of
       next crop