Maximum Yield Canada July/August 2017

plant analysis
The plant analysis lab report generated usually states
each of the macroelements (N, P, K, Ca, Mg, and S) as a
percentage of dry matter, while microelements (Fe, Mn,
B, Zn, and Cu), present in much lower concentrations, are
expressed as either parts per million (ppm), milligrams per
kilogram (mg/k), or micrograms per gram (μg/g). Some lab
reports will also include a guide to the ideal foliar level
range of each nutrient for specific crops to compare the
results against, but not all do. Instead, guidelines for the
most commonly grown hydroponic plants can be found
in plant nutrition books and websites that indicate ideal
levels for different species at different stages of growth. A
list of foliar mineral levels at which deficiency or toxicity
symptoms would be expected to occur are also useful to
have on-hand when comparing plant analysis reports.
“BY COMPARING
the foliar mineral levels
returned on a recent lab
analysis to the healthy
range for the plant
species being grown, it’s
possible to see which
nutrients fall outside the
recommended range.”
Top: Many disorders and diseases can have symptoms similar to mineral
deficiency/toxicities. Bottom: Foliar mineral analysis doesn’t take into
account nutrients incorporated into other parts of the plant, such as fruit.
When to Use Foliar Analysis
Plant analysis can be used for different purposes. It has a
vital role in crop research, where nutritional programs for
new crops may be determined by analyzing the mineral
content of well-grown, healthy plants. This data can then
be used to formulate nutrient solutions or soil programs
specifically aimed at maximizing plant nutrition for that
crop. For those running small trials, foliar mineral analysis
may be used to determine how different treatments,
supplements, products, growing environments, and
formulations affect the nutritional content of the plant.
For growers, the most common use of foliar analysis is for
when suspected deficiency or toxicity symptoms are starting
to show on plants. Since many physiological, disease, and
nutritional disorders can look quite similar, plant analysis is
often used to rule out or confirm specific nutrient issues so that
these can be rectified quickly and correctly.
Foliar analysis is often used alongside nutrient solution
analysis to determine necessary changes or supplements
to prevent deficiencies from continuing to occur. It is also
commonly used to confirm that nutrition has been optimal
and that the nutrient formulation is suitable for the current
stage of growth. Growers experiencing unexplained
symptoms such as an overall lack of plant vigour, plant
stunting, or low yields may use plant analysis to rule out
nutrition as the specific cause of any issues, or to diagnose
nutritional problems before they become more severe.
Interpretation of Plant Analysis Lab Reports
Recommendations for the ideal level of each nutrient in
foliar samples vary slightly, depending on the reference
source. For this reason, ideal levels are simply given
as a range within which most healthy plants should
fall. Typically, this is somewhat species dependant. For
example, normal foliar levels of nitrogen in crisp head
lettuce are often stated as being three to 4.5 per cent, while
in tomato, a crop requiring a higher level of nutrition, are
4.5-5.5 per cent; deficient levels would be less than two per
cent. For potassium, ideal foliar levels are 4.5 to eight per
cent in crisp head lettuce and four to six per cent in tomato,
with deficient levels being below two per cent.
Micro or trace elements often have a broader range of normal
levels in healthy plants. In tomato, iron levels should be
within the range of 80-200 ppm and manganese should be
between 50-300 ppm, with iron levels becoming deficient at
below 60 ppm and manganese below 20 ppm.
By comparing the foliar mineral levels returned on a recent
lab analysis to the healthy range for the plant species being
grown, it’s possible to see which nutrients fall outside the
recommended range. This can help pick up any potential
issues before a stage of deficiency has been reached and
plant growth becomes affected.
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