A Crop Thinning Demonstration
was held in Visalia on July 12, 2007 for CPGA members.
The following information is a summary of what was presented at the event.
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PECAN CROP THINNING
ASSUMPTIONS
Crop Setting
Characteristics
- Removing excess nuts by crop thinning in July
will NOT reduce the total weight of kernels produced at
harvest.
- The ratio of leaf surface to nuts is critical to
the trees ability to fill a crop
- Pecan trees have a limited amount of energy
dedicated to fruit production
- A Pecan tree can set more nuts than it has the
ability to properly fill with kernels
- The number of nuts to be set is determined by
tree stress and health in the late summer of the previous year
- Severely alternate bearing trees, free of stress
in an “off” year initiate a large number of nuts for the next year
- Severely alternate bearing trees under stress in
an “on” year will initiate a small number of nuts for the next year.
- Trees that produce a large crop of high quality
nuts (57 – 60% kernel) will initiate good crops for the following
year.
- Trees that produce a large number of poorly
filled nuts (45 – 55% kernel) will initiate small crops for the
following year.
- Alternate bearing occurs on an individual
tree basis in California orchards
- Crop thinning is not an acceptable long term
solution for deficient cultural imputs
Crop Thinning
Tips
- Ideally, thinning should occur prior to 50%
embryo development
- Prior to 50% embryo, thinning will have a
maximum effect on both current year quality and next years nut set
- After 50% embryo, the effect on next years set
is reduced, but current year’s quality is still improved
- Optimum thinning occurs during the period of
rapid sizing prior to shell hardening
- The “window” for thinning is usually a 2 – 3
week period in July
- Thinning after early September will have little
effect on current year quality nor next year’s nut set
- It is better to remove individual nuts from
clusters rather than entire clusters
- Tree bark will easily slip during the summer,
keep shaker pads well lubricated
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PECAN CROP THINNING PROCEDURE
Step 1: Strip an
overloaded tree of all its crop
- Study crop load
- Shake hard to remove nuts
- Estimate % left in tree
Example: 25%
- Remove trash and leaves
- Count number of nuts needed for one pound green
weight
Example: 100 green nuts per lb.
- Weigh all nuts under tree
Example: 60 lbs. of green nuts
- Multiply weight by number of green nuts per lb.
Example: 100 x 60 = 6,000
- Divide number of green nuts by 70 (dry Wichita nuts
per lb) = dry pounds per tree
Example: 6,000 divided by 70 = 85 dry lbs. per tree
Example: 85 divided by 75% = 113 dry lbs. per tree
- Multiply by number of trees per acre to determine
dry tonnage per acre.
Example: 113 lbs. x 48 trees per acre = 5,424 dry lbs. per acre at
harvest.
Step 2: Estimate
tree’s maximum load carrying ability
- Overall health of orchard
- Ratio of fruit to leaf surface and new growth
- Additional stress anticipated this year
- Previous large crop resulting in severe off year
- Previous large crop that resulted in poor kernel
yields
- Past thinning results
Example: Maximum desired production – 3,500 lbs. per acre
Step 3: Test shake
next tree to remove excess nuts.
- Calculate number of nuts to remove from each tree
Example: 1,000 divided by 48 trees per acre = 21 dry lbs. per tree
- Calculate number of green nuts per tree
Example: 21 dry lbs x 70 dry nuts per lb
= 1,470 green nuts
- Calculate number of green lbs. to remove from tree
Example: 1,470 green nuts per tree / 100 green nuts per lb.= 15 lbs
per tree
- Shake 3 – 4 seconds and weigh nuts
- Adjust as needed
- Repeat on several trees
- Repeat step 3 each day of thinning to adjust for
change in nut size
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