Foliar analysis reports returned from
the lab usually state macro elements
(N, P, K, Ca, S, Mg) as a percentage and
micro elements as either ppm or mg/Kg
which are equivalent. Some lab reports
will use a comparison chart to indicate
how the results stack up against optimal
levels for the plant species tested;
otherwise growers need to carry out
their own comparison. There are many
references for the ideal foliar minerals
for commonly grown hydroponic crops
and these may differ slightly from
source to source, often the ideal level is
stated as a range within which normal
healthy tissue should fall (Table1).
Nutrient Solution Analysis
Sending samples of nutrient solution
to an agricultural lab for analysis is
a common practice with commercial
growers, however, smaller systems also
benefit from this particularly where
recirculation of the nutrient solution is in
use. Much like a water analysis, nutrient
solution samples are collected in clean,
rinsed bottles and sent off to the lab as
quickly as possible. Samples can be
kept under refrigeration, if necessary,
before shipment. The most commonly
analyzed samples are of nutrient
leachate — that is the nutrient solution
that drains from the base of growing
containers/slabs or beds. These samples
give valuable information on how levels
of each of the specific nutrient ions
change as the solution flows through
Mixed crop systems using recirculating
nutrient solutions can have rapid changes in
nutrient ratios which are quickly picked up
by solution analysis.
the root system, thus identifying any
deficiencies, accumulation of elements,
or general changes in balance of
the nutrient formulation due to plant
uptake. Samples of nutrient taken from
recirculating systems such as NFT,
DFT, raft/pond type systems should be
carried out after the solution has been
in use for at least a week to assess how
the balance of nutrient ions is changing
over time. Data from these analysis
reports then can be used to make
adjustments to the nutrient solution —
elements that are declining over time
can be boosted and any accumulation,
particularly of any unwanted elements
such as sodium, can be identified. Use
of solution analysis allows a grower
to determine when a recirculating
nutrient solution requires replacement
to bring the balance of elements back
in line with optimal levels. Solution
analysis also allows a check to be
made of system equipment such as EC
and pH meters and probes. Samples
should be tested for EC and pH with
the grower’s meters before being
sent off to the lab; these can then
be compared to the lab reported EC
and pH levels which are taken with
fully calibrated equipment to ensure
accuracy levels. Nutrient solution
samples are typically sampled for: EC,
pH, nitrate, ammonium, total nitrogen,
phosphorus, potassium, calcium,
sulphur, magnesium, iron, manganese,
zinc, boron, copper, and sodium.
“
USE OF SOLUTION
ANALYSIS ALLOWS
a grower to determine
when a recirculating
nutrient solution
requires replacement
to bring the balance of
elements back in line
with optimal levels.”
Nutrient solution or leachate testing is a useful
diagnostic tool when symptoms start to appear.
Maximum Yield
41