JOHN NEYLAN JOHN NEYLAN
Summer
stresses ATM’s resident agronomic expert John Neylan looks back at the extreme summer endured by many superintendents and turf managers and writes about a surprising discovery he made while on a recent trip to a golf course in India.
Above: When soil temperatures rise above 18°C, cool-season turfgrass root growth begins to decline and ceases at 25°C. The declining roots are more susceptible to root rotting fungi and other stresses. New roots do not grow in hot weather to replace the old roots 48
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he summer of 2016/17 summer provided a range of weather extremes depending on what part of the country you were in. As you have no doubt already read in the earlier pages of this edition, it was one of the most challenging summer periods in a very long time, with the eastern seaboard from Sydney northwards in particular copping some record-breaking weather. The state-wide mean temperature in New South Wales was the third-highest on record for January, as was the mean maximum temperature, while the mean minimum temperature was fourth-highest on record for January. The exceptional warmth in New South Wales and southern Queensland persisted from January into February. Summer 2016-17 saw prolonged and, at times, extreme heat over New South Wales, southern Queensland, South Australia and parts of northern Victoria. In the Sydney region the highest temperatures of the period were recorded during 9-12 February, with Richmond reaching 47oC on 11 February. At a golf course in the same area, a top temperature of 49oC was also recorded. Under these conditions the discussion comes around to the management of cool-season grasses under such extreme temperatures and in particular the root system of creeping bentgrass (Agrostis sp.). Part of the challenge is the demand for firm and fast putting surfaces at a time when the grass should be placed into ‘survival mode’ by lifting cutting heights, applying fungicides and maintaining adequate moisture levels. It is also a prime time when all manner of products are promoted and used in an attempt to protect the plant and in particular the root system.
AUSTRALIAN TURFGRASS MANAGEMENT 19.2
When considering the root systems of heatstressed turf, thought needs to be given to how roots grow and whether it is possible to artificially alter the physiological damage caused by high temperatures. When soil temperatures rise above 18°C, cool-season turfgrass root growth begins to decline (Beard, 1973) and ceases at 25°C (Lucas, 1996). The declining roots are more susceptible to root rotting fungi and other stresses and new roots do not grow in hot weather to replace the old roots.
}Turf management under extreme temperatures is a matter of survival and has little to do with presenting an elite playing surface. Once temperatures are well outside of the accepted norm for turfgrasses, it is about minimising the stresses the turf manager can control. ~ Soil sensor data was collected from a golf course in Sydney and during January 2017 showed that the soil temperature was 25oC or greater every day except one and peaked at 35oC on two occasions (see chart on top of following page). The minimum temperature exceeded 23oC on 14 occasions! At a second site closer to the coast, the soil temperature data peaked at 29 C in February 2017. Clearly these