PETER McMAUGH AM
Ringing the
survival bell
ATM expert columnist Peter McMaugh AM discusses drought, turfgrass response and the role of rhizomes.
I
n the latter months of 2021 I received some documentation for review which was supposedly based around examining the drought hardiness of grasses. Its proposed definition included the following: ‘The aim of the trial is to ensure the drought tolerance of a target turf variety compared with benchmark varieties. The trial should be designed to subject the plots to increasing water stress for a period of 21 days or until 50 per cent of the turf in a plot has browned off or fired, whichever is sooner’. My immediate reaction was to say that 21 days without water did not constitute a drought, regardless of species and soil type. 46
The context of this communication was a normal home garden situation, so perhaps my reaction was too swift. I decided to cogitate on this a bit more. It seems to me that the major factors affecting drought, apart from the length of time without rain, are: l Is the grass cool- or warm-season? l What the soil type is in which the grass is growing? l How well-established the grass is? l What season of the year it is? l What climate zone it is in? When I look at the differences between warm- and cool-season types, the outstanding
AUSTRALIAN TURFGRASS MANAGEMENT 24.1
structural feature is how the stomate cells are structured and controlled. The relative number of stomates per square centimetre in the leaf surface is also important. The orientation of the leaves in a grass sward also has an influence on how quickly the sward loses water to the atmosphere. When we try to evaluate these influences of the grass sward rather than looking at individual plant structures, we quickly arrive at the interface we have with the irrigation demand of grasses to perform to the required quality level, which is different for every level of use, from high performance sport to roadside use.
