Salt Intrusion in Coastal Well Water: Diagnosing St. Augustine Decline

A Daytona Beach homeowner's St. Augustine turned brown after well water tested "15" for salt (units unclear). Neighbor's well failed from salt intrusion. The expert recommends soil and tissue testing before assuming well failure, plus compost for salt buffering.

Interpreting Salt Test Results

"15" likely means 15 mmhos/cm (electrical conductivity) or 1500 ppm TDS. St. Augustine tolerance: moderate (up to 8-10 mmhos/cm or ~8000 ppm). At 15 mmhos, salt stress is likely.

Differential Diagnosis

• Salt injury: Uniform browning, leaf tip burn, stunted growth
• Iron deficiency: Interveinal chlorosis on young leaves; high pH induced
• Drought stress: Wilting, footprinting, gray-green color
• Chinch bugs: Irregular patches, yellowing margins
• Brown patch fungus: Circular patterns, rotted leaf sheaths
• Winter dormancy: Uniform tan after freeze

Diagnostic Steps

1. Soil test: EC, SAR, pH, nutrients
2. Plant tissue analysis: Na, Cl, nutrient levels in grass
3. Well depth comparison: Shallow wells more prone to intrusion
4. Irrigation audit: Volume, frequency, timing

Management Strategies

• Compost topdressing: 3/8" thermophilic compost buffers salt, improves structure
• Gypsum (calcium sulfate): Displaces sodium on soil particles if SAR high
• Deep, infrequent irrigation: Leaches salts below root zone
• Acidifying fertilizers: Ammonium sulfate lowers pH, improves iron availability
• Consider alternative water: Reclaimed, municipal, deeper well

St. Augustine Specifics

Mow 2.5-3.5". Monitor for chinch bugs (summer), gray leaf spot (humid), SAD virus. Iron chelate foliar sprays give quick green-up if deficiency confirmed.

Test before investing in new well—soil/tissue analysis costs far less.