Maximum Yield Canada July/August 2017

plant analysis
“WHILE HYDROPONICS
may seem like the ideal
tool to provide the optimal
level of each element in
a well-balanced nutrient
solution, in reality, nutrition
is much more complex.”
Top: Researchers often use plant analysis to determine optimal nutritional
programs for new crops at different stages of growth. Bottom: Using
plant analysis of a well-grown soil crop can be used to formulate nutrient
solutions for new crops, such as these hydroponic peanuts.
of the element shown to be low or deficient in the nutrient
solution will not improve the problem. Other factors need
to be addressed. Calcium is a common example of this, and
iron is another. Calcium-related disorders such as blossom
end rot and tip burn in lettuce and many other plants are a
result of a lack of calcium incorporated into new developing
tissue. However, in hydroponics, where calcium is typically
supplied in most nutrient products at fairly high levels, a
lack of calcium in the root zone is hardly ever the cause of
the deficiency symptoms. In this case, low foliar calcium
levels on a plant analysis report are often a direct result
of growing conditions, which have limited plant uptake of
calcium from the hydroponics solution. These conditions
include high humidity, warm temperatures, and lack of air
flow. All of these restrict transpiration from the foliage, in
turn restricting calcium uptake and transportation within
the transpirational flow inside the plant. Increasing calcium
levels in the nutrient solution to address these low foliar
calcium levels (when levels are not actually deficient) will
not assist with induced mineral deficiencies.
Nutrient interactions can also induce nutrient deficiencies
in the foliar analysis tests despite there being no actual lack
of a particular element in the nutrient solution. An example
of this is in the use of high levels of ammonium, which also
restricts calcium uptake in the root zone. This can induce
calcium deficiency in the foliage and fruit of the plant that
subsequently shows up on the foliar analysis reports.
Under certain growing conditions, such as sub-optimal
temperatures, certain plants are unable to take up iron
or phosphorus efficiently and may show low foliar levels,
despite these elements being present in the nutrient
solution at good levels. If the plant roots have been
suffering from a root rot pathogen or root die-back, foliar
mineral analysis may show multiple deficiencies in many
nutrients; however, this is simply due to the root system
being unable to take up sufficient minerals from the
nutrient solution due to tissue damage. A lack of oxygen
in the root zone can also induce mineral deficiency. This
is also due to damaged roots being unable to take up the
nutrients required for healthy foliar levels.
To avoid these types of issues, it is usually beneficial to
carry out both nutrient solution and foliar mineral level
testing, particularly in recirculating systems where certain
nutrients may become depleted rapidly. This data can then
be used to determine if there is an ongoing problem with
the formulation, lack of any one essential element in the
nutrient solution causing low foliar levels, or another issue
effecting uptake and distribution within the plant.
Where the nutrient product or formulation is found to be the
cause of low, deficient, and even toxic levels of any element
as shown up in a plant analysis report, this data can then
be used to adjust levels in the nutrient solution. Increasing
deficient levels of most elements in the nutrient solution will
rapidly lead to higher levels of uptake and incorporation
into new leaf tissue. For some elements, particularly the
micro or trace elements, foliar sprays can also assist to
help quickly overcome a deficiency issue. A follow-up
leaf analysis can then be used to confirm the deficiency or
toxicity problem has been solved.
Plant analysis is likely to become an increasingly important
aspect of indoor hydroponic production as growers come
to understand more of the complexities of crop nutrition,
boosting growth, and maximizing yields. While hydroponics
may seem like the ideal tool to provide the optimal level of
each element in a well-balanced nutrient solution, in reality,
nutrition is much more complex, and a little monitoring
and plant analysis can go a long way to reaching the full
potential of the system.
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