Abstract
Potassium and chloride both suppressed Rhizoctonia blight in St. Augustinegrass and the two combined together as KCl was superior to K or Cl applied separately. Potassium applied as K₂SO₄ showed little disease suppression. Increasing rates of KCl on a Tifgreen bermudagrass green showed a strong correlation (r² = 0.9700) of reduction of dollar spot. K applied as K₂SO₄ and Cl applied as CaCl₂ had little effect. Glasshouse results showed increasing K applied as K₂SO₄ from 0 to 97.6 kg ha⁻¹ and Cl applied as CaCl₂ from 0 to 97.6 kg ha⁻¹ reduced dollar spot infection by 26% 1 week after inoculation. Bipolaris cynodontis infection on common bermudagrass in the field was reduced by 26% as Cl applied as CaCl₂ increased from 0 to 48.8 kg ha⁻¹ and K applied as K₂SO₄ increased from 0 to 48.8 kg ha⁻¹. Glasshouse studies showed increasing Cl applied as CaCl₂ reduced Bipolaris cynodontis on Tifgreen bermudagrass by 20% 1 week after inoculation and 30% 2 weeks after inoculation as rates of Cl increased from 0 to 97.6 kg ha⁻¹. Dollar spot infection of glasshouse-grown Tifgreen bermudagrass was reduced by 26% and 33% one and two weeks after infection as Cl applied a CaCl₂ increased from 0 to 97.6 kg ha⁻¹. Increasing K applied as K₂SO₄ reduced dollar spot by 26% and 21% one and two weeks after infection as rates of K increased from 24.4 to 97.6 kg ha⁻¹. Leaf tissue concentration of N was not affected by increasing rates of Cl applied as CaCl₂ or K applied as K₂SO₄ increased from 0 to 97.6 kg ha⁻¹. Leaf tissue K was not affected by Cl applied as CaCl₂ as rates went from 0 to 97.6 kg ha⁻¹ and increasing K above 48.8 kg ha⁻¹ did not increase leaf tissue K. Leaf tissue Cl decreased as K applied as K₂SO₄ increased from 24.4 to 97.6 kg ha⁻¹. Leaf tissue N from 20 to 24 g kg⁻¹, K from 13 to 16 g kg⁻¹, and Cl from 4.5 to 6 g kg⁻¹ had no effect on the infection by Bipolaris cynodontis on field-grown common bermudagrass.
Rider, Larry Ray (2001). Relationships between potassium, chloride, and disease incidence in St. Augustinegrass and bermudagrass. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -2001 -THESIS -R53.