36
Almond Facts
JULY | AUGUST 2017
IN YOUR ORCHARD
weather and that is not near equipment or fuel storage.
Stockpiles should be oriented in a north-south direction
to aid in drying and covered with white-on-black tarps.
Monitor humidity and open the tarp when appropriate to
reduce condensation and mold formation. Also monitor
and treat for insect, bird, and rodent pests. If rain
threatens, ensure piles are covered. Finally, be aware that
stockpiles are a potential fire hazard.
Stockpiles should be fumigated to reduce insect
infestation. NOW is an excellent storage pest and can
survive in stockpile conditions. Furthermore, this pest
can continue to feed and reproduce within stockpiles,
increasing damage as well as aflatoxin risk. Although time
consuming, fumigation is critical in killing larvae and
eggs, reducing damage.
Be wary of too much moisture in stockpiles. Studies
have shown that hull moisture above 14% and a holding
temperature greater than 120°F will increase the risk for
concealed damage and mold. If needed, delay harvest
until nuts can dry. If already in stockpiles, remove tarps
during the day to dry and cover at night. If harvesting in
rainy conditions, keep the nuts in the tree if possible to
aid in drying. If already on the ground, try to encourage
drying by removing leaves, twigs, and other material.
This may take several passes with the pick-up machine
or conditioner.
Postharvest Irrigation
and Nutrition
The initiation of fruit bud formation occurs for most
almond varieties in mid- to late August. Severe stress
imposed during this period can reduce floral bud count
and fertility in the following years. Trees should be
irrigated as soon as possible after harvest to reduce stress.
During this period, the tree is also building nitrogen stores
for the following year. Approximately 20% of the nitrogen
budget should be applied in the post-harvest period. The
rate may be reduced if mid-July leaf samples were above
2.5%. No more than 50 lbs of nitrogen should be applied,
however, as research has shown that the shorter days and
lower ETc demands limits the amount of nitrogen uptake
to about this much for a mid-August harvested variety.
Rates for later harvesting varieties should be less. There
probably is minimal value in applying nitrogen after the
beginning of October.
Hull Analysis for Boron
Boron is an important micronutrient for almonds. Boron is
critical for flower fertilization, as it is involved in directing
the germinating pollen tube. Deficiencies lead to reduced nut
set, and in severe cases, an appearance of a “nonproductive
symptom.” Within the tree, boron deficiency can lead
to gummy nuts in the spring, dieback of small twigs and
a “weeping branch” look. Boron is also toxic at high
concentrations. Boron toxicity is often observed in areas with
high soil boron or in blocks irrigated with water containing
boron. Boron toxicity symptoms appear as gummy nuts
that may form «stick tights,” as well as gum exuding from
pruning wounds, bud and leaf scars, and spurs.
Critical threshold levels for boron hull values are as follows:
To determine if an orchard is deficient in or showing
toxicity from boron, hull samples must be collected.
Since the hulls serve as the primary boron sink, they
tend to accumulate the nutrient, and provide a consistent
reading. Leaf values are not effective in determining
adequate boron levels, regardless of timing. Furthermore,
leaf tissues cannot reliably detect toxicities and are
inconsistent at the lower end of the sufficiency levels.
Boron deficiency can be alleviated through applications of
boron to the soil. Caution should be used when determining
the rate of material applied, as high rates of application
may cause toxicity. Generally, a one to two pound/acre of
elemental boron is a reasonable soil application (~10-20 lbs
of a 20% boron product). There have been some reports
that boron applied in the summer may lead to stick-tights at
harvest, suggesting that it may be better to apply boron after
harvest. A foliar spray of boron should always be considered
between postharvest and pinkbud.
The Final Thought
Over the past few years there has been an increase of
almond thefts. These include from stockpile yards and
missing truckloads. Although it is a busy time, be mindful
of the activity and stick to the protocol of verifying drivers
and receiving signed pickup sheets. In larger operations,
consider assigning only the most trustworthy employees to
handling trucking and delivery information.
Hull Boron Level (PPM)
Deficiency
<80 PPM
Sufficient
100 - 160 PPM
Toxicity
>300 PPM
