eNEWS
June 2009 > UF Research: Amending soil with silicon to enhance disease resistance
by Dr. Amanda J. Gevens, Dept. of Plant Pathology, University of FL/IFAS, Gainesville, FL
Dr. Lawrence E. Datnoff, currently at Louisiana State University, Plant Pathology and Crop Physiology Dept.
Chair, Baton Rouge, LA
The focus of this research is to further
understand the interaction between
plant disease and mineral nutrition in
organic production systems. Florida
organic growers are challenged to produce
quality vegetables because environmental
conditions are often conducive for the
development of plant diseases. Although
cultural techniques are often integrated
with other management tools, plant
disease can still reduce vegetable yield and
quality. As a consequence, other strategies
must be developed for the control of plant
pathogens and the diseases they cause.
One component of such an integrated
pest management (IPM) system is the
potential use of silicon as a tool for
disease control. Although silicon is not
considered an essential element for
plants, it has enhanced the growth and
development of several monocot and
dicot species, especially under poor soil
and nutrient conditions. Silicon has
also provided effective control of both
soilborne and foliar fungal diseases. This
project continues to investigate amending
the soil with naturally mined silicon
minerals to enhance disease resistance.
The use of silicon as a soil amendment
offers a potentially sustainable method
of addressing plant disease control while
improving soil health and crop quality.
Experiments were started in Fall 2007 at
the University of Florida’s organic research
plots in Citra. The site was
selected because it was initially very low
(≤4 ppm) in silicon. Previous research has
demonstrated that soils less than 19 ppm
are considered to be extremely low in this
element. The cucumber cultivar ‘Straight
Eight’ was selected for the experiment
because it is very susceptible to a number
of plant diseases and produces fruit of a
typical commercially accepted size and
shape. The experimental design was three
silicon rates X two years with a two level
cover crop factor as a split treatment. This
cover crop factor has occurred during the
non-cash crop period when the plots were
split so that one half is seeded with either
rye grass (winter) or sorghum (summer).
All treatments were arranged in a
randomized complete block design with
four replications. Silicon amendments
were applied at three rates: 0, 200, 400,
and 600 kg of elemental silicon/ha.
Wollastonite (calcium silicate, CaSiO3),
a naturally occurring mined mineral ore,
was the silicon source used. Cucumbers
were grown following the NOPS.
In 2008-2009, we carried out a spring
and fall crop of ‘Straight Eight’ cucumber
with a summer cover crop of
sorghum and a winter cover of rye. Both
cucumber plantings experienced heavy
Downy mildew (Pseudoperonospora
cubensis, pictured above) disease pressure that
was unaffected by silicon treatment.
Additionally, our fall planting experienced
frost conditions at maturity, which
negatively impacted plant health and
fruit development. The plants’ response
to frost was unaffected by rates of silicon
treatment. Plant tissue was collected for
silicon analysis at transplanting, first
flowering, first fruit set, and two weeks
before last harvest. All data are being
processed and analyzed to determine the
overall contribution of silicon to organic
cucumber production over time.
For more information contact Florida Organic Growers at 352.377.6345 or email fog@foginfo.org.