Optimizing Bermudagrass Resilience: The Impact of Fertilizer Timing

Maintaining healthy, durable turfgrass is a constant challenge for sports field managers and homeowners alike. For warm-season grasses like bermudagrass, balancing growth needs with environmental regulations – particularly summer fertilizer restrictions – presents a unique hurdle. Recent research sheds light on how fertilizer timing and frequency impact bermudagrass’s ability to withstand wear and tear, offering valuable insights for sustainable turf management.

The Challenge: Balancing Turf Quality and Environmental Concerns

Bermudagrass is a popular choice for sports fields and lawns in warm climates due to its strong resistance to trampling and quick recovery through its extensive root system. However, many regions implement fertilizer restriction periods, typically from June 1 to September 30, to protect water quality by minimizing nitrogen and phosphorus runoff during the rainy season. This restriction coincides with both peak bermudagrass growth and peak field usage, creating a conflict between maintaining turf health and adhering to environmental policies.

Recent Research: A Two-Year Field Trial

Researchers at the University of Florida conducted a two-year field trial (2022-2023) in Citra, Florida, to investigate the effects of different nitrogen fertilizer application strategies on ‘Bimini’ bermudagrass. The study, published in the journal Agronomy, compared four treatments:

• Fortnightly Fertilization: Nitrogen applied every two weeks (24.4 kg N ha^-1 per application).
• Monthly Fertilization: Nitrogen applied monthly (48.8 kg N ha^-1 per application).
• Pre-Ban Single Application: A single, larger nitrogen application before the fertilizer restriction period (97.6 kg N ha^-1).
• Control: No nitrogen fertilization.

To simulate real-world conditions, a traffic simulator was used to apply 60 simulated trampling events annually. Researchers assessed turf performance by measuring Percent Green Cover (PGC), Dark Green Color Index (DGCI), soil moisture content, surface hardness, and rotational resistance during both “trampling” and “recovery” periods.

Key Findings: Frequent Fertilization Promotes Resilience

The study revealed that consistent, regular nitrogen fertilization – either biweekly or monthly – significantly outperformed a single pre-ban application, particularly under sustained trampling stress.

• Trampling Period: Throughout both years, biweekly and monthly fertilization maintained higher PGC and DGCI compared to the single pre-ban application and the control group.
• Recovery Period: During the recovery phase after trampling ceased, the consistently fertilized lawns exhibited faster and more complete recovery, again with biweekly and monthly applications leading the way.
• Soil Properties: Even as effects varied slightly between years, frequent fertilization generally improved soil moisture content and reduced surface hardness.

The research suggests that consistent nitrogen supply supports tillering, lateral growth, and canopy density, creating a stronger turf system better equipped to distribute and absorb stress. A single large application may not provide sufficient nitrogen throughout the restriction period to support ongoing tissue regeneration and canopy maintenance.

Implications for Turf Management

These findings have important implications for sports turf managers and homeowners facing fertilizer restrictions. Where regulations allow, adopting a staged fertilization strategy – applying nitrogen in smaller, more frequent doses throughout the growing season – is a more effective approach than relying on a single pre-ban application. This strategy balances environmental protection with the need to maintain high-quality, durable turf surfaces, ensuring player safety and fair play.

Looking Ahead

Further research is needed to explore the optimal nitrogen rates and timing for different bermudagrass cultivars and under varying environmental conditions. Understanding the interplay between soil properties, nitrogen loss pathways, and other management practices (like mowing and irrigation) will be crucial for refining turf management strategies and achieving sustainable turfgrass health.