Revitalizing "Wichita" Pecan Productivity Through Corrective Pruning - First Year Results
Director, County Extension, Pinal County
Michael Kilby, Specialist, Plant Science
A pruning study was established in stressed pecan trees to identify effective means
of returning unproductive trees to full productivity. The study was comprised of two
pruning systems and one untreated check. The number of nuts harvested from pruned trees
was lower than that harvested from the unpruned trees, but the quality of the nuts from the
pruned trees was improved when compared with the unpruned trees.
Reduced yields in low altitude pecan orchards are a common problem in Arizona.
Yields over 2,000 pounds per acre are common through out the pecan belt of North America while
yields in low altitude orchards in Arizona often average 1,700 pounds per acre. These reduced yields
can negatively impact the economic viability of orchards.
Reduced yields are often traced to environmental or nutritional stresses endured by the tree.
Stressed trees will often show shortened internodes; small, sparse leaves, reduction in male and
female flowers; as well as poor fruit retention and nut quality. In an attempt to identify ways
to rejuvenate stressed trees, an orchard pruning trial was established in 1997.
Eighteen "Wichita" trees were selected in a block from a section of an orchard showing
severe stress symptoms near Casa Grande, Arizona. Six trees were left unpruned as a check.
The remaining twelve trees were either severely headed back or moderately headed back.
All treatments were applied in a completely random design. Nut quality data were collected at
harvest in December of 1997. Yield data and nut quality data will be collected during the
1998 and 1999 harvests. Nut samples were collected from trees dropping fruit during harvest.
Those samples were evaluated for nut quality parameters. Results were tabulated and are recorded
in Table 1.
Results and Discussion
Only four moderately pruned and one severely pruned tree produced nuts during the first year
after pruning. At the same time, all six unpruned trees did produce nuts but the average nut size
and the percent kernel of those nuts were lower when compared with the nuts from the treated trees.
Table 1 lists the number of trees dropping at nuts at harvest,
the average nut size and the average percent kernel from each treatment.
The average nut size from the severely pruned tree was 6.41 grams compared with 6.26 grams
from the moderately pruned trees and 5.83 from the unpruned trees. The percent kernel from the
severely pruned tree was 60% while the moderately pruned and unpruned trees produced percent kernel
of 56 and 55% respectively.
This is a part of publication AZ1051:
"1998 Citrus and Deciduous Fruit and Nut Research Report," College of
Agriculture, The University of Arizona, Tucson, Arizona, 85721.
This document located at http://ag.arizona.edu/pubs/crops/az1051/az105116.html
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