Dethatch the dry spot with a dethatching rake to remove debris from around the base of the dry grass that prevents nutrients and moisture from penetrating through to the roots. Roots that fail to receive sufficient water, nutrients and sunlight turn brown and become dry and weak. Removing accumulated grass clippings and debris can restore the healthy color of the grass.
Water the dry spot immediately if it occurs soon after you fertilized the area. Excessive nitrogen burns the grass, causing it to turn dry and brown. Direct a gush of water using a hose over the dry spot to dilute fertilizer concentrations.
Aerate the soil under the dry spot in spring to allow moisture to reach the roots. Soils exposed to frequent foot traffic compact as the soil particles become tightly bound, preventing moisture penetration. This is identified by accumulated pools of water over the dry spots after a rainfall instead of draining. Use a core aerator to pull plugs of soil out so water and air easily penetrate through to the roots.
Douse the dry spot with water if you notice the dog urinating over it. Dog urine is highly acidic and contains excessive amounts of nitrogen that burns the grass, causing it to turn brown and dry. Frequent dog urination over a particular patch of grass causes nitrogen to accumulate, robbing it off its natural color. A heavy spray of water removes urine concentrations and dilutes its effect.
Water the dry spots in your lawn grass immediately if the soil underneath feels dry and crumbly. Ideally, the soil 4 to 6 inches below soil level should remain evenly moist for healthy and lush green grass. To prevent the occurrence of fungal diseases, water the soil in the morning or early afternoon so the grass blades are dry by evening.
Inspect the grass for damaging pests such as clinch bugs, sod webworms and army bugs that cause the grass to turn dry and brown. Clinch bugs turn healthy grass brown so it resembles drought-stressed grass. Sod webworms create patches of dead grass, while army webworms eat entire grass plants down to the soil. Treat the dry spot with an appropriate fungicide to prevent the problem from growing out of hand.