Yellow spots near sprinkler heads on my lawn?

Yellow spots around sprinkler heads are typically caused by overwatering, fertilizer burn from concentrated nutrients, or dog urine damage. The most common culprit in New Brunswick is overwatering combined with our clay-heavy soils that don't drain well.

Overwatering is the primary cause, especially in areas like Fredericton and the Saint John River valley where clay soils are common. When sprinkler heads deliver too much water or run too frequently, the soil becomes waterlogged and oxygen-starved. Grass roots literally suffocate, turning yellow and eventually brown. This is particularly problematic during New Brunswick's humid summers when evaporation is slow and our soils already hold moisture well.

Fertilizer burn occurs when liquid fertilizer injected through the irrigation system becomes too concentrated near the heads, or when granular fertilizer gets caught in the spray pattern and receives repeated watering. The high salt content burns the grass, creating distinct circular yellow patterns. This is more common with automatic fertilizer injection systems.

Dog urine damage creates similar circular yellow spots, often with a ring of darker green grass around the perimeter where diluted nitrogen acts as fertilizer. Female dogs typically cause more damage due to their squatting behavior concentrating urine in one spot.

Check your sprinkler timing first. In New Brunswick's climate, lawns need about 1 inch of water per week including rainfall. During our typically wet springs and falls, you may not need irrigation at all. Run sprinklers early morning (5-7 AM) for deep, infrequent watering rather than daily light sprinklings. Clay soils need longer, slower application rates to prevent runoff.

Inspect the spray patterns to ensure heads aren't overlapping excessively in those areas. Adjust spray radius or replace heads if they're creating too much overlap. For clay soils common in central New Brunswick, consider installing rotary nozzles that apply water more slowly, allowing better soil penetration.

Test your soil in the affected areas. If it's compacted clay that's staying soggy, core aeration in late August will help. Add compost to improve drainage in problem spots. If it's fertilizer burn, flush the area with water and avoid fertilizing those spots for 6-8 weeks.

When to hire a professional: If you have an in-ground irrigation system that needs pressure adjustments, nozzle changes, or timer reprogramming, a landscaper experienced with New Brunswick's soil conditions can optimize your system. They can also perform soil testing and recommend drainage improvements for persistently soggy areas.

Need help finding a landscaper experienced with irrigation systems? New Brunswick Landscaping can match you with local professionals who understand our Maritime climate and soil challenges.