34
Almond Facts
SEPTEMBER | OCTOBER 2015
Time To Consider
DAVID DOLL
When planning a new orchard, it is important to consider location,
water availability and quality, irrigation system selection, pre-
plant soil modification, rootstock, and variety selection. Mistakes
made during the planning process will be present throughout the
orchard’s life. Below are some considerations to keep in mind when
selecting a site, rootstock, and variety.
Site Selection and Modification.
Soil typ
e - Soils that have a high water holding content can be
problematic when trying to access the orchard in early spring.
Furthermore, these soils may also increase the risk of “wet
feet” and
Phytophthora
infections. Rocky soils can make orchard
operations like harvesting and mowing challenging, but generally
can be managed unless it is more rocks than soil. Saline-alkaline
soils will have challenges with water infiltration. These soils often
require pre-plant leaching or modification to leach salts.
Salinity -
Soil salinity should be below1.5 dS/m as an average
of the rooting depth (five feet). To determine the salt levels, soil
samples should be collected from each of the differing soil types
in the field.. Sample plugs or auger cores of each soil type in 4-5
locations. At each location, sample every 12 in of depth to 60 in.
Combine and pool samples at a given depth (e.g. combine and
mix 4-5 samples at 12 in depth, 4-5 samples at 24 in depth etc).
A composite sample should be pulled for every 20 acres, with a
minimum of three samples for smaller fields.
Nematodes -
When soil sampling, collect for salinity, set aside
some of the soil from the 12-24” depth samples for nematode
analysis. Submit the soil to a lab that can test for nematodes. For
almond and other stonefruit, nematodes of concern are ring, root
lesion, and rootknot. If counts are greater than 50 per liter (or 500
grams) of soil for root lesion and rootknot, or 25 for ring, contact
the local UC Cooperative Extension farm advisor for specifics
TIME TO CONSIDER
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on pre-plant soil treatment options. Some common
species of root lesion nematodes feed primarily on
weeds and are of little concern to almond growers.
Therefore you must request that the lab identify which
species of root lesion is present.
Water source -
The source of irrigation should be
considered when planting. This includes the quality
and quantity. Ideally, water should be less than 1.0
dS/M in EC, with a sodium adsorption ration (SAR)
less than 3, chloride under 5 meq/L, and boron under
0.5 mg/l (0.5 ppm). Water pH should be 7.2 or less,
and may need to be amended if it is too alkaline. If
the SAR is greater than three, gypsum should be used
to increase calcium levels. If water contains higher
amounts of sodium, chloride, or boron, either an
in-season or dormant leaching program should be
planned, which will require 15-30 percent more water,
depending on the salt concentration. Gallons per
minute of a well should be known prior to establishing
the irrigation system.
Soil pH -
Soil pH over 7.5 will make some
micronutrients bind more strongly to soil particles and
reduce their availability to be taken up by plant roots.
. Low pH will also effect micronutrient availability,
especially if pH is below 6. If the soil is highly alkaline (or
acidic), and amendments can not reduce (or increase) soil
pH adequately, poor growth and deficiency will occur.
Ideally, the range is between 6.4-7.5, with peach-almond
hybrids performing better in alkaline soils. Acidifying
agents may help reduce pH in alkaline soils, although the
amounts needed to modify the soil are often very high.
In acidic soils, lime should be considered to help increase
the pH into the desired range.
Soil stratification -
Soil layering can create
problems with water infiltration. Backhoe pits should
be dug to determine if soil layering occurs and if the
soil should be modified. Soils with stratifying layering
in the top four feet probably require some type of
modification. If the soils contain multiple clay lenses,
slip-plowing may be the best option, while deep
ripping is often sufficient to break up hard-pan layers.
If you decide to modify a soil, consult with a local
Extension advisor for details on local soil conditions.
When modifying soils, the shank length must be 1.5
times greater than the targeted depth of modification.
Water table -
If in a high risk area, dig backhoe pits
to determine the depth to the water table. If the water
