Moisture key to turf cover survival
Moisture management is key to recovery from turf cover loss over the summer, and protecting vulnerable surfaces from further damaging effects in the following season.
Initial results of new Syngenta turf health strategy trials at STRI in Yorkshire this season showed that, even with a level of irrigation, untreated clean cut turf surfaces suffered up to 35% loss of turf cover through hot, dry summer periods of June and July. Even into September turf cover on the untreated plots was still 30% less, compared to early June.
For areas treated with Qualibra wetting agent, however, turf cover was retained within less than 5% loss through the same June to July period, and never more than 5.5% loss right through the prolonged stressful periods into September.
The trials have highlighted the risk of turf cover loss through the increasingly common challenge of extreme heat and prolonged dry weather, which can just overwhelm many existing irrigation systems.
It also demonstrated the essential role of effective wetting agent strategies to maximise utilisation of available soil moisture and give turf plants greater resilience to withstand weather extremes.
While most turf can withstand some periods of drought, when that is combined with high light intensity the cumulative stress can be overwhelming. That has particularly been the issue over the past summer. Furthermore, where dry patch develops in hydrophobic soils, - which effectively repel water droplets and lose the ability to hold soil moisture – then rainfall or irrigation runs thorough without benefit to revive turf.
Restoring soils’ moisture holding capacity and limiting the effects of dry patch build-up after prolonged drying out will be hugely important for successful overseeding to recover lost turf cover, along with giving greater survival of plants against future drought periods next season.
Seed germination
STRI trials have also shown the beneficial effect of Qualibra wetting agent applications for overseeding success, through a combination of improved germination and stronger establishment.
The application of Qualibra at 20 l/ha five days before sowing provided a 200% increase in in bentgrass germination assessed 18 days after sowing, with a 250% increase in germination with ryegrass turf species.
That led to significantly stronger growth within a month and, assessed 49 days after sowing, over 50% turf cover in Qualibra treated fescue areas compared to just 17% in untreated. In the ryegrass there was a 100% increase in cover over the same period.
It is a difficult balance to manage the appropriate amount of moisture to enable germination and seed establishment, along with quick recovery, but not keeping the surface damp for long periods of the day which could create conditions for disease to establish, as well as affecting playability.
Holding moisture lower in the soil profile with Qualibra encourages rapid root growth to reach moisture, whilst surfaces can still be effectively held drier and faster – which is also less conducive to seedling diseases.
In STRI trials Qualibra programmes at full rate prior to sowing achieved the best results, but even half rate applications achieved a significant boost in seedling establishment.
Furthermore, once seedlings are established, moisture management will be key to assuring survival during more frequent prolonged dry periods, especially on unirrigated areas and fairways.
For many extensive thinning of grass cover has now occurred three to four times in the past decade. With predictions that it is likely to be more frequent in the future. Selecting turf species and varieties to transition to surfaces more resilient to drought and heat stress is going to become more important, but takes time for seed breeders to select for and assess.
Cost savings
Significant cost and time savings can be made where reseeding and recovery actions can be avoided, along with developing more sustainable strategies that use less carbon-cost resources. That includes wetting agent strategies across fairways and wider parts of the course, along with improved turf rooting to increase utilisation of available water and nutrition.
More efficient use of available water resources is clearly desirable, with significant investment is being made in more controllable irrigation systems on many courses to cut wastage. To get the most out of irrigation systems it’s essential to balance available soil moisture as a factor of rainfall and irrigation water applied, vs evapotranspiration losses.
That can be calculated on an individual golf course scale with the Turf Advisor App weather data and irrigation records. It is also far more powerful if you can link that to records of soil moisture monitoring of surfaces – either manually with meters or remotely with in ground probes - to interpret the lasting effects from applying a set amount of irrigation water or rainfall under prevailing weather conditions.
All Syngenta trials in the development of new wetting agent technologies use moisture probes buried at set depths in the soil profile. These record and transmit data 24-hours a day, to monitor how changes in moisture at depth affect turf quality performance, turf health and playability conditions.
Hydrophopic sand
With most overseeding operations incorporated into surface renovation and improvement programmes, many now opt to integrate seed application directly with sand injection, or top dressing over intensive verti-draining.
View the effects of Qualibra in countering hydrophobic soils
However, with this strategy it is important to assess sand sources and the risk of already hydrophobic sand. This may occur where sand has been held in a bay ready for use for some period, particularly during intense hot periods, or older sand is being recycled.
Where seed is sown in hydrophobic sand that could add additional moisture stress, unit roots can reach into water retaining treated soils. Where these conditions occur Qualibra application straight after the topdressing or sand treatment can help to alleviate issues through the germination and establishment phase.
Summer stress
It’s not just moisture stress that impacts on turf health and survival over the summer. Multiple stress factors can interact, with the cumulative effect far more severe than the individual parts.
There is good evidence that when a plant is naturally responding to a primary stress through gene regulation at a molecular level, such as heat, if another stress from mowing damage or light, for example, impacts it then takes longer to adapt, and more damage is done.
While Qualibra gave the strongest beneficial responses of cover retention, the Syngenta turf health research at STRI also showed that Ryder pigment alone provided 20% better results compared to untreated. Other new development biostimulants targeting specific summer stresses and overall turf health also consistently retained improved turf performance and cover at similar levels.
Integrating all the technologies into turf health strategies that will help retain both in season playability and reduce the costly and time-consuming practice of repeatedly reseeding.
