Spotlight on turf health

Light is the key element of photosynthesises that drives health and performance of turf plants, along with water, nutrition and CO₂. Yet, in most situations, its management has previously been limited to cutting back vegetation to reduce the adverse effects of shade. 

Now, as with all spheres of science and research, the more we understand about an issue and the better we can measure the scale of the problem, the greater the opportunity to do something about it, writes Syngenta Technical Manager, Pete May in Greenkeeper International.

With all the tools now available to better manage the influences of light on turf performance, along with the techniques to understand where and when they can be best utilised, greenkeepers have the chance to hugely improve turf health and consistency of surface conditions. 

Research has shown how some grass species and cultivars are more effective in low light situations or, increasingly importantly in climate shift conditions, how some can better withstand high light intensity. Finer grass species, such as bent grass , for example, can be particularly hard hit by low light levels with short days or shaded conditions. 

Abiotic turf stress research at the STRI and Syngenta-sponsored PhD studies at Harper Adams, for example, have shown how in low light conditions a Primo Max II programme can help to mitigate health and turf quality effects. 

Studies concluded the physical growth regulatory action holds back the vertical extension of leaves in search of light in shaded or low light conditions, and encourages stronger lateral growth. That improved density enables greater green leaf area for light absorption, an improvement in playability and no reduction in ball speed. Scientific research has demonstrated how Primo Maxx II growth regulation increases the concentration of chlorophyll in the leaf and enhances photosynthetic efficiency, enabling plants to perform better in low light conditions. 

In recent years we have had innovative pigment technology in Ryder that can enable turf plants to mitigate the effects of excess light causing stress and cell damage within the leaf. 

New technologies could see those same properties available to build into future agronomy programmes without resorting to coloured pigments – making the benefits available to links courses, for example, where light intensity can be particularly severe, but a more naturalistic turf colour required.

Now, Syngenta research with Vyplenza biostimulant has shown the potential to enhance the plant’s ability to utilise available light. That’s crucial in high light intensity situations, where excess light to the plant’s requirements can cause intense stress - primarily in mid-summer, but also late spring when light can be strong but temperatures or water availability limits plant activity. In these conditions Vyplenza has been shown to uplift the plant’s natural genetic activity in response to light intensity by up to 23%. 

What is most exciting, is that we can begin to build up layers of protection against the adverse effects of light in mid-summer.

And then, going into the autumn as light levels begin to fall, genomic testing has shown the Vyplenza programme can give a 53% increase in genetic activity associated with photosynthetic light harvesting.

That is becoming even more significant, with climate shift making the situation ever more challenging. Historically, as conditions for growth slowed down later in the season, the light requirement for performance correspondingly reduces. 

However, with a warming climate and generally more available moisture in the later season, turf wants to continue to grow, but with the light levels rapidly falling turf can frequently be left in a stressful energy deficit. That imposes greater stress and impact on turf health and vigour, at the very time when microdochium patch disease can thrive in the mild wet autumn conditions. 

 It’s well documented that average DLI (Daily Light Integral) levels fall by around 25%-30% per month through the autumn. The DLI is a measure of the number of photons of Photosynthetically Active Radiation (PAR) light that falls on a surface over a 24-hour period, which is effectively the useable light by the plant. 

Even with climate shift, the duration of day length doesn’t significantly change; there may be some effect of greater light intensity without cloud cover, but that effect is only marginal, compared with then other effects of climate shift.

US research, at Arkansas University,  showed creeping bent grass, for example, typically requires a Daily Light Integral (DLI) of around 30 to maintain healthy turf quality. Syngenta research at STRI using light management technologies, however, indicated that comparable optimal turf health could be achieved at a DLI of 25, compared to a typical DLI 30 in untreated turf. When light levels are low that could make a significant difference.

The implication is that where Vyplenza is being used to enhance the photochemical efficiency of harvesting available light, plants can continue to perform more effectively and reduce the impacts of stress at lower DLI. 

We now understand that once light levels exceed around 600-700 micromoles per m²/sec, then the turf plant’s ability to photosynthesise and convert sunlight energy into carbohydrate plateaus.

At best the excessive light is wasted, but when coupled with other factors, such as extreme soil temperatures, low soil moisture or low nutrition the additional stress could in fact be extremely damaging.

When measuring overall light availability through the day, you also have to consider the duration of light intensity. While three or four of strong light in the middle of the day may appear to provide sufficient total energy, in reality plants can only utilise a certain level of light at any one time and any excess is wasted - or worse still physically damaging – with other hours at lower intensity providing insufficient energy to support optimal plant growth.  That can be particularly apparent in autumn and early spring, where morning and late afternoon light is weak.

One of the keys to the changing management techniques has been the ability to measure and record light intensity on turf surfaces more effectively. At its simplest, a hand-held light meter can better quantify impacts on different areas of a green at any given time, and help prioritise greenkeepers’ actions to reduce the effects. 

Once you move up towards installed meters that constantly measure and record light intensity and duration, such as the Syngenta SPIIO currently in use for UK R&D and turf management in the US, it gives the potential to tailor decision making and treatment timing to make best use of available technologies.