Silicon: a new tool for promoting turf health?

Silicon and plant health

• 1920s: silicon shown to induce resistance/tolerance to diseases and increased yields in rice

• Calcium silicate now typically applied to rice, sugarcane and other crops for increased yields and pest tolerance

• Benefits for turfgrass are now being investigated at Univ. of Florida, elsewhere

Composition of the earth’s crust

1.5All others2.1Magnesium2.6Potassium2.8Sodium3.6Calcium5.0Iron8.1Aluminum

27.7Silicon46.6Oxygen

Approximate% by weight Element

Most silicon in the earth’s crust is complexedwith other minerals and is unavailable for plant uptake

Al 2 SiO 4 (F, OH) 3, Aluminum silicate fluoride hydroxide

TOPAZ

Silica is a three dimensional network of silicon dioxide, most commonly encountered as ?

Zeolite: hydrated aluminosilicate

Not to be confused with Silicones:synthetic polymers containing silicon

Silicon is not considered an essential element except for plants related to horsetails (Equisetum)

How does silicon prevent disease in plants?

Physical resistance:Deposits in cuticle or epidermal cells may inhibit fungal penetration

Biochemical resistance: good evidence in rice that silicon triggers formation of compounds that are toxic to fungi

(coumaric, ferulic, salicylic, cinammicor caffeic acids; chitinase, peroxidase, phytoalexins)

Powdery mildew and wheat: physical and biochemical resistance

What do we know about silicon and turf health?

• 1999: Better wear tolerance on bent, zoysia

• 2000: Brown patch tolerance in zoysia• 2002: gray leaf spot

suppression/control on St. Augustinegrass when used pre-plant

• Contradictory results from other labs on brown patch, GLS

Suppression of gray leaf spot on St. Augstinegrass.South Florida, 2000

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(20 lb elemental Si/1000)

Silicon and turf health

• Effects mirror those seen in rice: disease suppression rather than disease control

• Turf results vary from lab to lab• If soil levels are higher than 40 ppm

(Melich III), addition of silicon to the soil may have no effect

Silicon concentrations in golf course soils (Melich III)

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greens tees fairways All samples

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Analysis of silica

• Acetic acid extraction is preferred: 19 ppm in soil is desired concentration

• Melich III extraction may not be as accurate, and will produce higher values (at least 2X)

Silicon concentrations in golf course soils

• Levels seem to exceed those required for enhanced disease control, but:– We used the Melich III method, which is

not widely used by silicon researchers– We have tested fewer than 20 samples– We will conduct a survey of golf course

soils and compare Melich III to acetic acid extraction values (in collaboration with Dr. Lawrence Datnoff’s lab at the University of Florida)

Silicon and turf health

• Effects mirror those seen in rice: disease suppression rather than disease control

• Turf results vary from lab to lab• If soil levels are higher than 40 ppm,

addition of silicon to the soil will have no effect

• If products are applied at low rates, addition of silicon will have no effect

Silicon sourcesCalcium silicate slag• A dry powder of pellet derived from

limestone slag, a by-product of the steel industry

• Contains 22% available soluble silicon• Products include Recmix (Reclime, Sarver,

PA) but are not commonly available in CA• At the recommended rate of 50 lb/1000 sq

ft, slag provides 11 lb silicon/1000 sq ft• Rice, wheat, sugarcane studies conducted

using pre-plant applications, incorporated into soils

Silicon Complex 7% (Grigg Bros: Logan, UT)

Silicon (SiO2) ….................................... 7.0%

Complexed with organic and amino acids

Analysis

• Univ. of Florida proposed target rate for disease, plant health is 11 lb soluble silica/1000 sq ft

• At 1-3 oz/1000 sq ft, this product provides 0.07 – 0.21 oz silica/1000 sq ft (0.12%, or 1/833 the recommended rate)

Roots Stand-Up (Roots/NovozymeBiologicals: Salem, VA)

Guaranteed Analysis:Available Phosphate (P205> ..............2%Soluble Potash (K2O) ......................12%Silica (Si) .....................................7%Derived from: Potassium Silicate, Tri-PotassiumPhosphate and Potassium Hydroxide.Non Plant Food Ingredients: Humic Acid.

• Proposed target rate for disease, plant health is 11 lb soluble silica/1000 sq ft

• At 3 oz/1000 sq ft, this product provides 0.21 oz silica/1000 sq ft (0.12% recommended rate)

Sili-Kal-B (Grigg Brothers: Logan, UT)

Total Nitrogen (N).................................. 8.0%7.0% Nitrate Nitrogen1.0% Urea Nitrogen

Available Phosphoric Acid (P2O5)......... 0.0%Potassium (K)........................................ 4.0%Boron (B)................................................ 0.5%Calcium (Ca).......................................... 10.0%Silicon (Si).................................. 0.01%

Analysis

• Proposed target rate for disease, plant health is 11 lb soluble silica/1000 sq ft

• At 3 -6 oz/1000 sq ft, this product provides 0.0003 -0.0006 oz silica/1000 sq ft

Future work• Soil survey to determine whether golf

courses would benefit from silicon applications

• Comparison of Melich III to acetic acid extractions to identify the best method for measuring silicon

• Identifying products, rates and application methods that are practical for golf courses and testing these in the field