Summer fertilization of St. Augustine grass growing in moderate shade should be avoided because of increased disease activity. St. Augustine lawns may require periodic applications of iron sulfate or iron chelate to prevent iron chlorosis. A foliar application of iron sulfate at a rate of 6 to 8 ounces per 1,000 square feet effectively eliminates the symptoms of iron chlorosis. These applications may be needed several times during the growing season. Iron chelates should be applied according to the manufacturer's directions.
Uniform distribution is essential to prevent light and dark streaks across the lawn.
For better distribution, divide the fertilizer to be applied into two equal lots. Fall Fertilization Fall fertilization is the key to prolonging fall color and promoting early springs recovery of lawns. It also helps to produce a dense turf which resists winter weeds. Fertilizers used in the fall should be high in nitrogen and potassium and low in phosphorus. Grass fertilized in the fall with nitrogen and potassium have shown greater survival during winter months and faster spring recovery than grasses fertilized with high phosphorus materials in the fall.