The Nutrition of Almonds

Phosphorus
Calcium
Almonds have a low requirement for Phosphorus (P)
but P is essential for plant growth, especially for
energy transport and production of carbohydrates.
Trees suffering from P deficiency have stunted growth
and leaves and shoots remain smaller than normal.
Phosphorus applications need to replace P removed
in harvested nuts, approximately 6-13 Kg P/ton and
provide additional P for permanent tissue if the trees
are still growing. Application of P should be made
during the “End of bloom to mid fruit development”
Calcium improves potato tolerance to diseases
and during “Post-harvest” in fertigated systems.
Potassium
Almond trees take up almost as much Potassium (K)
as nitrogen (N) and a K deficiency will reduce nut yields
and quality. Each ton of almonds removes 50-75 Kg of
K depending on variety. Potassium is needed for starch
formation, translocation of sugars and to regulate
turgor pressure (opening and closing of stomata). A
mild to moderate K deficiency is unlikely to be seen
except for overall slow growth, which reduces yield
potential. A more severe K deficiency causes leaf
margins to die and leaf tips to curl upward and overall
health is adversely affected. Significant yield loss will
result if the K deficiency is severe enough to cause leaf
symptoms.
Almonds are known to be sensitive to salinity buildup
in the root zone, which can reduce yield potential.
An increase in root zone salinity can be caused by
many reasons. Common contributing factors include;
irrigation water quality, soil type and structure, soil
drainage, annual rainfall and K fertiliser source. By
having a good understanding of the relative influence
of each of these factors, root zone salinity can be
managed, allowing all K fertiliser sources (chloride,
sulphate, nitrate and phosphate) to be considered
when designing a crop fertiliser program. With this in
mind, K can be supplied to almonds in the most cost
effective manner.
The majority of Calcium (Ca) in plants is found in the
cell membranes and cell walls where it plays a critical
role in maintaining cell membrane integrity and cell
wall strength. Localised Ca deficiencies are usually
found at the growing points because Ca is immobile
within the plant. These disorders caused by localised
Ca deficiencies are referred to as physiological diseases
because the physiology of the plant is adversely
affected but no pathogen is involved. An adequate
concentration of Ca in plants helps reduce or eliminate
physiological disorders and also helps plants resist
fungal and bacterial pathogens by suppressing the
extracellular enzymes that the pathogens secrete.
The beneficial effects of Ca on nut crop diseases is
shown in research of hazelnuts. Results from 3 years
of field research have shown that applying 40 or
80 kg/ha of Ca as YaraLiva Tropicote in early spring
markedly reduced the incidence of mouldy nuts at
harvest and after 10 or 18 days in storage (Figure
2). The same rate of nitrogen was applied in all
treatments but YaraLiva Tropicote replaced the growers
standard practice which supplied no Ca.
Calcium is essential for nut retention and applications
are most effective in early season and post-harvest.
Figure 2. Summary of 3 year study
investigating the benficial impact of soluble
calcium on mould incidents in Hazelnuts
Monitoring orchard K status
Leaf samples provide a good window into the K
nutritional status of Almond orchards. Minimum
critical leaf value for K is 1.4% and values less than
this are likely to be associated with yield loss and
adverse effects on overall health. Recent research
has shown that leaf K levels should be in the
1.6-1.8% K range for optimum tree health and top
yields.
Yara I 5