4. • It took the Millenium Drought to show that
C4 grasses would survive in Melbourne
without any irrigation
• Some people assume it’s just a 25-30%
saving in water with C4 turfgrasses
• And, with no water restrictions, there has
been some movement back to C3 grasses
• The summer performance of C4 turfgrasses
is a package, with several components
9. 2. Cell membrane function
C4 cell lipids work best between 27 – 35oC
C3 cell lipids, work best between 16 – 24oC
(melt down above 40oC or so)
10. 3. C4 turfgrasses don’t suffer Heat Stress
or High Temperature Kill
C3 turfgrasses experience Heat Stress due to a
lack of evaporative cooling when foliage
temperatures exceed 32oC or so. At 42oC or so,
the cells melt down (High Temperature Kill)
C4 turfgrasses: tolerate foliage temps of 60oC for
10 hours, without damage
13. Increasing C4 root growth as
summer goes on
C4 ‘Spring Root
Decline’
July Aug Sept Oct Nov Dec Jan Feb Mar Apr May June
30
25
20
15
10
0
C4
14. C3 root growth period
C3 root recovery
C3 ‘root dysfunction’
July Aug Sept Oct Nov Dec Jan Feb Mar Apr May June
30
25
20
15
10
0
C3
15. 5. Time of year when roots are weakest
and the turf is most vulnerable
C4 turfgrasses: Spring Root Decline
C3 turfgrasses: late summer into autumn,
root dysfunction
16. 6. C4 turfgrasses quickly resurrect
from drought stress (e.g. from
summer rainfall).
C3 turfgrasses won’t recover from
summer drought stress until late
autumn.
20. 7. Most C4 turfgrasses have rhizomes
Couch, Kikuyu, Zoysia and Carpet Grass have
strong rhizomes (not Seashore Paspalum or
Buffalo, though).
C3 turfgrasses: Kentucky Blue, and to a small
extent Tall Fescue and Fine Fescue, and
Browntop Bent have some rhizomes. But not
Ryegrass, Bentgrass.
21. 8. Summary of drought resistance:
Water Budget
C4 turfgrasses: 0 – 5 ML/Ha per summer
(very flexible)
C3 turfgrasses: 8 ML/Ha per summer
(not negotiable)
22. 9. Traction and ACL injury?
AFL theory: couchgrass causes ACL injury
because of high rotational traction
There is a greater difference between one
boot and another boot, than between C4
and C3 turfgrasses
23.
24. 10. Oversowing
You can successfully and sustainably oversow a C4
sward with a C3 grass (e.g. Couch or Kikuyu with
Perennial Rye) for better winter performance.
But you can’t oversow a C3 grass with a C4 grass
for better summer performance.
25. 10. You can oversow a C4 grass with
a C3 grass, but not vice versa
Winter oversowing of Couch or Kikuyu with
Perennial Ryegrass is an excellent technique
to improve playability and colour, and protect
the underlying C4 grass.
But you can’t oversow a Perennial Ryegrass
field with Couch or Kikuyu to improve
summer performance.
30. There are other differences too (e.g. growth
habit, salt tolerance, Poa control options,
traffic tolerance etc).
If people aren’t reminded of all these benefits,
there will be a push to go back to C3 grasses
when water is plentiful.
That’s without even mentioning climate change.
