LIGHT TRIALS
Extended lighting may help in areas shaded by stands
T E C H N I C A L U P D AT E
SPOTLIGHT ON SHADE
Syngenta trials at STRI provide an insight into the effects of shade on sports turf ryegrass, and those results can now be used alongside our knowledge of the potential impact of too much light to create the optimum integrated management plan for playing surfaces
A By Glenn Kirby Syngenta Turf UK technical manager
24 THE GROUNDSMAN May 2019
better understanding of how light works and how plants utilise light will enable you to get the best from lighting, whether that’s high-tech light rigs, controlled-environment tents or the sun. Studies have shown that once light levels exceed 600-700 micromoles per m2/sec (determined using a light meter to record Photosynthetically Active Radiation, or PAR), the turf plant’s ability to photosynthesise and convert light energy into carbohydrate plateaus. At best, light in excess of 600 micromoles is simply unutilised by the plant. But if there are any other limiting factors or stresses on the plant, such as nutrient or moisture deficiency or compaction, the effect of excess light can be even more damaging. The implication is that light units can be highly beneficial to supplement light levels when they are low, but it could be important not to oversaturate plants with too much light.
Light readings in stadium shade have shown intensity can be reduced by 85 per cent; even dappled shade, from fences, structures or trees surrounding training grounds and pitches, for example, typically excludes around 40 per cent of light on turf areas.
LET THERE BE LIGHT
Measuring light during short season days, from late autumn through to early spring, means we can understand the severe restrictions it creates in trying to manage turf grass. However, studies of the daily light fluctuations have shown that, even where the total light measured would indicate sufficient is available, if the plant has been unable to fully utilise the high peaks through the middle of the day then there could be a serious shortfall of the plant’s requirement. On a bright early-spring day, turf surfaces in southern England, for example (see graph), would appear to get good levels of sunlight,