February 2023 - 18

PRODUCTION
MAINTAINING
Water Quality
Understanding and managing your water effectively
can improve production quality in the greenhouse.
BY HEATHER MACHOVINA
A
n important factor to consider in any greenhouse
is the quality of water being used to irrigate the
crops. Many growers will face crop challenges that
can be traced back to the quality of water they are using
and its affect on pH and electrical conductivity (EC) in the
root zone, says Brian Bourdon, senior manager of offsites
and crop supply chain at Four Star Greenhouse Inc.
" Knowing your water quality will allow you to be
proactive rather than reactive in producing high-quality
crops, " he says.
" Certain genera grow much better at a low pH
(petunias), others at a high pH (geraniums), while some
crops like New Guinea impatiens prefer low feed levels
(low EC) and others, like petunias, prefer high EC. "
Knowing these differences can be helpful, but also
overwhelming, when trying to grow multiple crops in one
greenhouse. " I often tell growers to worry less about
the specifics and try to maintain a general pH in the root
zone of 5.8 to 6.2 and EC of 0.6 to 1.0 when using the
1:2 method for testing, " says Bourdon. He adds that most
crops will grow well in these ranges, but depending on
your water source, these goals can be difficult to achieve.
WATER QUALITY BASICS
Getting a water test from a reputable lab to analyze
your water quality is a great first step. These tests are
affordable and can save you a lot of problems.
" Even if you are on a municipal source like we are here
at Four Star Greenhouse, it's still a good idea to send
samples out to be tested, " Bourdon says. Municipalities
tend to have consistent results throughout the year, but
Four Star still tests at least twice per year to be sure. Well
water can vary more and should be tested more frequently.
Bailey Nurseries tests its water quality at different
frequencies, depending on the location. Jean-Marc
Versolato, Midwest plant health department manager at
Bailey Nurseries in Minnesota, says the water is tested
18
FEBRUARY 2023 GPNMAG.COM
The copper ionization system used at Bailey Nurseries.
ALKALINITY
One important aspect of the water test results is the
total alkalinity level, which has a big impact on pH in the
root zone. The pH of your water test is good to know but
does not impact the rise or fall of the pH in your root zone,
according to Bourdon.
" Knowing your alkalinity is crucial to knowing which
fertilizers to use on a regular basis, " he says. " With
moderate alkalinity levels (50 ppm to 125 ppm), you
can usually have good success with the right fertilizers
alone but, as alkalinity levels rise, pH of the root zone
becomes a greater challenge, and you may need to look
at additional solutions. "
A common method is acid injection with the amount
of acid needed depending on alkalinity level. Sulfuric
acid is probably the most common, but nitric, citric and
phosphoric acids can also be used, Bourdon says. Each
has their own advantages and disadvantages, and it's best
to research the right fit for your operation.
three times per week for pH, alkalinity and copper, since
they use a copper ionizer to sanitize the irrigation water.
At the Oregon location, greenhouse water is tested weekly
during the growing season, and monthly outside of that
time, for pH, EC, sodium hypochlorite, and alkalinity.
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February 2023

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