WCN Dec e

Continued from Page 29 exuded by microbes bind soil particles ‘
into aggregates and earthworms burrow
through soil, creating channels for
water and air flow. Microbial metabolites
chelate micronutrients, delivering
iron, zinc and other elements to roots
in plant-available forms. Beneficial
fungi extend the crop’s root system,
exchanging water and nutrients for
photosynthate and signaling when to
activate stress defense mechanisms.
Microbial biomass also provides
nutrient storage, releasing plant-available
nitrogen, phosphorus and other
elements as populations turn over.
such as hydrogen, calcium, potassium
and magnesium, and anions, including
hydroxide, nitrate, borate and molybdate.
Binding with organic matter prevents
essential nutrients from leaching
to groundwater or precipitating out of
soil solution with other minerals. Ions
buffer into or out of soil solution to
maintain chemical equilibrium, keeping
pH near neutral and replenishing
nutrient concentrations in response to
plant absorption.
The living fraction of soil organic
matter drive all of the activity contributing
to healthy soil development.
Fungal networks, beneficial bacterial
populations, earthworms and more
contribute to carbon cycling and
organic matter fixation. Micro and macroorganisms
decompose raw organic
matter, returning essential elements to
plant available form. Sticky substances
Highly productive,
carefully managed
orchards might not
show any changes
in yield or crop quality,
but better soil
health may allow
growers to decrease
water and fertilizer
use while maintaining
productivity.
Feed the Soil its Carbon
Microbial activity, nutrient cycling,
and structure development require
carbon. Almonds and other tree crops
feed the microbiome by sending photosynthate
down to the rhizosphere, but
significant improvement in soil quality
requires more biomass. Feeding microbial
populations by growing cover crops
and applying compost or mulch can
help achieve net carbon gain, initiating
the processes that build organic matter
and improving agricultural sustainability.
Soil structure and beneficial microbial
ecology take time to develop.
During the first few years of cover
cropping, the orchard might require
more water and fertilizer to establish a
robust cover crop stand without jeopardizing
the crop’s access to sufficient
moisture and nutrition. Over time,
the investment pays off. Incremental
increases in organic matter ramp up
the soil’s capacity to sustain diverse,
active microbial populations. Increased
microbial activity accelerates humus
formation and the other beneficial
soil characteristics follow. Improved
nutrient availability, soil moisture and
beneficial microbes can improve tree
health, reducing symptoms of micronutrient
deficiency, drought and salinity.
Measurable improvements in water
holding capacity, bulk density and
nutrient availability may take several
years to develop. Soil type, management
practices, weather, water, fertilizer and
many other factors influence organic
matter accumulation and soil health.
While some soils may respond quickly,
others resist organic matter fixation.
Very sandy soils lack the clay particles
that bind and stabilize organic matter,
preventing accumulation. The type of
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30 West Coast Nut December 2021