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Q: How do I use phosphite products in my garden?
Thanks, Scott Taylor
P
hosphite products really started to gain
popularity within the turf industry in the
1990s as an effective and relatively less toxic
alternative to standard chemical fungicides.
Phosphites are effective at stopping the
development of and controlling the spread
of the Pythium fungus, commonly referred
to as root rot. However, phosphite products
do not contain any phosphorus (P) in the
phosphate form, which is the form that is
readily available for uptake by roots and is
involved in the formation of DNA as well
as the facilitation and storage of chemical
energy produced through photosynthesis.
There are a number of phosphite fertilizers
available that claim to increase flower and
fruit production. These products are usually
labeled with an N-P-K ratio of either 0-30*-20
or 0-30*-30, with the asterisk denoting nonplant-available phosphite. Phosphite products
are made by mixing phosphorus acid
and potassium hydroxide. The resulting
solution, called potassium phosphite,
renders the phosphorus unavailable in
the phosphite form with the potassium
existing as the soluble potash (K2O) ion,
a plant-available form. Any increase in
flower production from the application
of a fertilizer containing phosphite
will undoubtedly have occurred due
to the elevated levels of plant-available
potassium. Although current research
has shown that in certain conditions,
phosphites can indeed be converted,
over time, to the phosphate form
by specialized soil bacteria, it is not
considered a reliable way of providing
phosphorus to developing plants and is
best used as a foliar or soil application to
suppress the growth of fungal pathogens.
Hope that helps,
Kyle
Kyle L. Ladenburger is a passionate indoor and outdoor gardener. He is also
a freelance garden writer. With nearly 10 years in the industry working for Age Old
Organics, H\