By having a well-designed and well-thought-through water treatment
plan, growers can continually improve their water quality.
“My water treatment goal is very different,” he said.
“My goal is to deliver water that is going to produce
the healthiest plants possible. I have learned over
the nearly 30 years of being a biochemist and
studying water treatment that accomplishing that
goal will take care of the other goals related to
mechanical issues and the destruction of potential
plant pathogens.”
While incorporating chemicals into their water
supplies can keep the growers’ equipment clean
and control pathogens, Hayes cautions that these
same chemicals can have an adverse effect on the
growers’ plants.
“Plants can be sensitive to oxidizers,” he said. “Even
though growers may not be seeing any negative effects on the plants, these chemicals may be affecting plant growth. The beneficial microbes around
the plant roots may also be negatively impacted.”
Hayes said the most common oxidizers used for
greenhouse vegetable crops include different forms
of chlorine, chlorine dioxide, ozone and peroxide.
“Some oxidizers are more prone to phytotoxic
effects than others,” he said. “With all oxidizers,
it is a case of what is the target level, what level
is being taken up by the plants and how well
can that level be controlled? Many growers don’t
24
understand and know what level of oxidizer
residual is being delivered to their plants. This can
occur with any of the oxidizers. The control system
that is used to inject and monitor the oxidizer is
critical. Some oxidizers are very pH sensitive and
in order to work correctly the pH has to be within
a narrow range. Other oxidizers create byproducts
that can be phytotoxic or have negative effects on
the plants depending on what inorganic or organic
compounds are in the water.”
Avoid a pieces-parts system
Hayes said a common mistake made by growers
trying to install a water treatment system is they
look at it as a component purchase.
“A grower thinks he needs a filter so he buys one
and installs that into his irrigation system,” he said.
“Then the grower may consider adding an oxidizer
to treat the water and adds that to his system. What
eventually happens is the grower has installed a
conglomeration of components that are dispersed
throughout his system that were never designed
to work together. Some of those components can
cause problems for each other and sometimes they
can leave gaps in the system.”