April 13, 2018
CapitalPress.com
15
Prune orchards of the future may vary
By TIM HEARDEN
For the Capital Press
RED BLUFF, Calif. — What will
the prune orchard of the future be
like? It depends on a variety of fac-
tors, researchers say.
New orchard layouts could de-
pend on soil types, while new crop
management techniques and new va-
rieties other than the now-dominant
French prune could resist diseases
and reduce the need for thinning,
said Franz Niederholzer, a Universi-
ty of California Cooperative Exten-
sion pomology farm adviser.
“The way it looks now may not
be the way it turns out,” Niederhol-
zer told about 60 growers during a
recent workshop in Red Bluff.
Niederholzer gave attendees elec-
tronic devices to vote in instant sur-
veys and asked them to envision the
“perfect orchard.” Majorities indi-
cated they would want it to produce
6 dry tons per acre with spacing of 18
feet wide by 14 feet between trees.
Asked what they think are the
biggest obstacles to planting prunes
in 2018, most growers cited prune
prices and cost of production, in-
cluding pruning costs. Most growers
said their next plantings would be
entirely new orchards rather than in-
terplanting.
In actuality, optimal spacing can
depend on soil types, which can in-
fluence a tree’s production. Soil can
vary even in small blocks, and Nie-
derholzer suggested that growers
consider soil mapping and matching
spacing and irrigation to the map.
“Consistent production is really
important,” he said.
Also, planting and managing
trees in such a way that it maximiz-
es sunlight on the trees will increase
yields, he said. In a recent newslet-
ter, he explained that replacing an
orchard spaced 18 feet-by-16 feet
with one with rows 17 feet or 16
feet apart could increase per-acre re-
turns by as much as $760, assuming
a $2,000-per-ton average dry fruit
price to the grower.
While new planting schemes
can boost production, researchers
are looking into ways to improve
orchard health by developing new
rootstocks.
UCCE advisers have been evalu-
ating alternative rootstocks in Cali-
fornia Dried Plum Board-supported
field trials throughout the Sacramen-
to Valley.
Among the research:
• Scientists in Butte County are
testing rootstocks that reach full
bloom at different times, with the
intent of spreading out bloom timing
and reducing the risk of a crop fail-
ure because of bad weather, accord-
ing to a UCCE prune newsletter.
Prune production took a nosedive
in 2016 after cold, wet and windy
weather created adverse conditions
for bees during the height of polli-
nation.
• Farm advisers are watching
disparities in tree trunk sizes on test
plots in Butte and Yuba counties, ac-
cording to the newsletter.
The trees with larger trunks in
Butte County had a higher dry yield
per tree, a higher “dry away” ratio
(the ratio of green fruit weight to dry
fruit weight) and smaller fruit, while
the smaller-trunked trees had lower
dry away ratios and larger fruit.
This tree size and yield dispari-
ty may be partly caused by soil and
water differences between the sites,
researchers said.
In the prune orchard of the fu-
ture, a grower choosing a rootstock
will need to consider whether the
objective is to plant larger, more vig-
orous trees or to plant smaller trees
at a higher density, the newsletter
explained.
University of California Cooperative Extension pomology farm adviser Franz Niederholzer says such factors as rootstock choice and cropload management will
determine how prune orchards perform in the future. Photo by Tim Hearden/For the Capital Press
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