Sports Turf Agronomy Advice - May 2026
As we move into May and the final stages of transition from spring into early summer, turf managers once again find themselves navigating a period of challenging growing conditions.
While longer daylight hours and improving temperatures are beginning to support growth in some areas, the impact of overall unfavourable growing conditions is continuing to influence surface performance and recovery.
This spring has presented a contrast of conditions. Periods of warm, bright days have been interspersed with cooler nights, which has slowed consistent growth and placed the plant under intermittent stress. Soil temperatures have gradually increased, but fluctuations in moisture availability have meant that growth has been inconsistent across different sites, particularly where irrigation is limited.
April was highly variable, characterised by sharp swings between unseasonably warm, dry conditions and cooler, unsettled periods. Yet again, what we used to consider as extremes are now just the norm; the thought of a consistent spring seems a thing of the past and, as turf managers, this difficult transitional period is something to adapt to and perhaps slightly adjust practices in order to achieve the best performance possible, given the conditions.
The cold nights combined with bright, sunny days and limited moisture created a classic spring stress scenario for turf as we progressed through April. The warm sunny days increase the photosynthetic rate within the plant, so it is working hard, at this key time of year. There is increased Evapotranspiration (ET) at a time you don’t really want to apply extremely cold irrigation water, in April these rates were exacerbated by strong drying winds. The cold nights with morning frosts slow the metabolic rate right down, affecting the plants recovery rate.
Physiologically, the stomata close to conserve water, this reduces photosynthetic efficiency, energy production is inconsistent which leads to a limited growth response from the plant and rooting is restricted. These factors lead to an increased risk of localised dry patch development and surface inconsistency (patchy growth, variable colour) . The challenge here is that to the untrained eye, conditions are conducive for good growth (sunny, warm days) so surfaces should be establishing well. But in reality as turf managers you are nurturing a plant under cumulative physiological stress.
The forecast for May suggests more settled conditions, with moderate temperatures and fewer extremes than experienced earlier in the spring. Night-time temperatures are expected to remain more consistently above 8°C, which will support more reliable growth patterns. Where adequate moisture is available either through rainfall or irrigation this should lead to improved recovery and sward density. However, for sites with limited irrigation capacity, dry conditions may continue to place stress on the plant and restrict growth potential.
Key Management Considerations
Water Management
Efficient water use remains a priority as we move into a period of higher demand:
- Raise heights of cut where possible to reduce plant stress
- Inspect irrigation systems to ensure uniform coverage and identify leaks
- Use moisture meters to guide precise irrigation decisions
- Prioritise hand-watering of localised dry areas over blanket applications
- Irrigate to replace only the deficit via ET to reduce over watering.
- Continue the use of wetting agents to improve water distribution and retention
These practices will help maintain surface performance while conserving water resources.
Nutrition
Nutritional programmes should remain flexible and responsive to growth:
- Apply nitrogen in line with growth potential rather than fixed schedules
- Adapt planned applications in line with changing conditions for optimum results
- Be mindful of nutrient loss where irrigation has been high
- Incorporate biostimulants such as seaweed and amino acids to support plant health under stress
Balancing inputs with growth demand will be key to achieving consistent surface quality.
Seaweeds are a traditionally used biostimulant to help mitigate stress on turfgrass. In turf management there are a variety of seaweeds on the market from different sources, Brown seaweeds (Phaeophyceae) such as Ascophyllum nodosum are used most. These have excellent stress mitigating qualities due to their ability to deal with stressful growing conditions, out of water for half the day and under water for half the day. The effectiveness of a seaweed application is down to the compounds within the seaweed when it’s applied, these differ depending on the extraction method used during the production process, but some of the key ones are:
Polyphenols: Give advanced antioxidant protection and stress resilience
Polyphenols are powerful naturally occurring antioxidants that play a crucial role in defending turfgrass against oxidative stress. These compounds help neutralize reactive oxygen species (ROS) generated during periods of drought, high temperature, or salinity
stress, thereby preventing cellular damage. In turfgrass, elevated polyphenol levels strengthen the plants defence system, enhance cell wall stability, and contribute to overall plant health and longevity.
Alginates: Improve root stability and water retention
Alginates are complex polysaccharides naturally found in Ascophyllum nodosum that play a crucial role in enhancing soil plant interactions and promoting root development. In turfgrass, alginates improve soil structure by binding particles and increasing water retention around the root zone, creating a more stable environment for growth. They also act as natural chelating agents, improving nutrient availability and uptake efficiency, vital for maintaining healthy, dense turf in high-stress environments.
Proline: Optimises stress resilience
Proline is an important amino acid that helps turfgrass survive in high abiotic stress conditions. When turfgrass is under stress, heat, drought, shade, salinity, high pH or cold, proline levels naturally increase. This boost acts as a sign that the grass is activating its built-in protection system, helping cells stay healthy and recover more quickly.
Mannitol: Enhanced water balance and stress recovery
Mannitol is a naturally occurring sugar alcohol found in Ascophyllum nodosum extracts that plays a key role in helping turfgrass cope with stress. Acting as both an osmo-protectant and antioxidant, mannitol supports water balance within cells and protects plant tissues from oxidative damage caused by heat, drought, or salinity. Elevated mannitol levels indicate that the turf is better equipped to maintain turgor pressure, sustain photosynthesis, and recover more effectively after stress.
Laminarins: Strengthened natural defence and recovery response
Laminarins are natural polysaccharides that play a vital role in strengthening plant defence mechanisms. Acting as powerful elicitors, laminarins activate the plants innate immune system, triggering the production of defence related enzymes and stress protective compounds. This response enhances turfgrass resilience against environmental stress and disease pressure, while also supporting steady growth and recovery. Elevated laminarin levels indicate that the turf is physiologically primed to respond faster and more effectively to external stress factors.
Pest Activity
May typically signals the beginning of increased pest activity:
- Chafer grubs (May beetle) may begin to emerge - monitor adult activity to inform control strategies
-
Leatherjacket populations may still be active; where damage is evident, nematode applications can be effective
- Steinernema feltiae can be applied at soil temperatures above 8°C
- Steinernema carpocapsae is suitable above 13°C
Accurate identification and correct timing of treatments are essential for effective control.
Tom Wood
B.Sc (Hons) | MBPR | FQA