Pogo Turf Pro System Manual page 83

Canopy Temperature
The most influencing temperature on turfgrass performance is the canopy temperature. Many may not know that the fundamental process of
Photosynthesis depends not only upon light efficiency, but it also depends on the temperature, as the turf sees it, to be less than 86 degrees F (30
degrees C). This is not the ambient temperature that determines this. And it is not the underlying soil temperature either. It is the temperature in
the canopy of the turf system. While the effects of this threshold are seen quickly in C3 or cool season turf (Creeping bentgrass, Poa annua, etc.),
C4, or warm season grasses (bermudagrass, zoysiagrass, Seashore paspalum, etc.) too are hindered when the canopy temperature climbs too
high.
However, due to the nature of C4 grasses and how they store compounds used in Photosynthesis, this tolerance is slightly higher than C3 grasses
and falls in the range of about 89 to 93 degrees F (31 to 34 degrees C). Above this level, even the more efficient C4 grasses will suffer from too
high canopy heat. If your moisture level is not optimum (i.e. poor moisture/air ratio), you are securing a fate you don't want in the very near
future. As moisture is maintained optimally, the turf system causes a cooling effect rather than a heating effect.
It is quite possible and happens often that the canopy temperature is higher than the ambient air above it. Further, this canopy temperature is
greatly affected by the amount of moisture present in the top 5.5 cm (2.2") of the turf system. This moisture conducts heat very well from the
sunlight above. This heat then remains through the cool part of the day (and night) when the turf would rather benefit from the subsequent
cooling down of the system. Imagine that your turf system holds on to this heat through the night. Then the next day more heat is added. More
and more heat is added in the following days until there is simply no relief from the heat in the turf system. This happens far too often and is
greatly influenced by our moisture management practices.
In this condition, we see Photosynthesis non existent and we see a great loss of turf vigor and performance. It all starts with understanding the
stresses on the system and how each variable impacts them...which POGO measures precisely and easily. Also note that as temperature rises, the
impacts of EC become greater and greater on the influencing stress on turf performance.
Photosynthesis not only is influenced by temperature as noted here, it depends on free water movement and availability in addition to the
free exchange of CO out of the soil system...which only occurs when air and water balance is optimal.
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