Overton, Texas
March 25, 2005
An agricultural researcher here is
looking at using perennial tall fescues in East Texas as
possible replacement annual winter forages.
"The problem with the annual winter forages is that they have to
be replanted every year," said Dr. Gerald Evers, forage
management expert with the
Texas Agricultural Experiment Station.
Winter forages allow beef producers to reduce one of the largest
out-of-pocket costs during the winter – feed costs. But
re-establishing winter forages every year is expensive. On
average, a producer spends from $20 to $40 per acre in seed
costs, fertilizer and field operations, Evers said.
Tall fescues are perennials, and unlike winter annuals such as
ryegrass, could – if managed correctly – last years. But current
fescues, though well adapted for climates and soils in the
Midwest, are not so well adapted to most soils in southern
climates, he said.
The sandy soils of the South are the limiting factor in
maintaining a tall fescue stand in East Texas, Evers said. Tall
fescues become dormant as average temperatures rise and the
length of day increases in early summer. Becoming "dormant"
means they cease growing and shut down many of their metabolic
processes.
But a summer rainfall can "wake up" tall fescues, causing new
top growth, regardless of temperature and day length. As the
sandy soils of East Texas and the South quickly dry out, the
summer temperatures cause the new growth to die. It is this
cycle of dormancy, wake-up, then dormancy again, that can kill
out tall fescue stands, Evers said.
"Repeated growth initiation followed by senescence of top growth
... causes depletion of carbohydrates in the root system,
resulting in grass stand deterioration," he said.
Another issue is that tall fescues are infected with a fungal
endophyte that is toxic to beef cattle and other livestock.
Endophyte is Greek for "in the plant," meaning the fungus grows
throughout the plant's tissues and is not confined to its
exterior.
Though not lethal, the endophyte's toxic effect on animal health
becomes more severe during the summer. Animals grazing older
fescues realize lower weight gains, experience reproductive
problems and, in extreme cases, have reduced blood circulation
to their extremities.
Ironically, this same endophyte confers grazing tolerance and
drought and disease resistance to tall fescue.
"Without the endophyte cattle will graze out tall fescue and
kill a stand in two or three years," Evers said.
But Evers suspects both these detriments to many U.S.-grown tall
fescues may not be present in new varieties of Mediterranean
origin now being developed in New Zealand.
First, these varieties cease growth when day length and
temperatures rise regardless of serendipitous rainfall. These
varieties are know as "obligatory" summer-dormant types.
"A preliminary experiment planted at Vernon, Texas, in October
2000, proved that an obligatory summer-dormant tall fescue had
superior summer drought resistance and persistence after three
growing seasons," Evers said.
Second, some varieties carry an endophyte that is not toxic to
animals. Called "endophyte safe," these fescues have the same
grazing tolerance and drought and disease resistance as the
older fescues.
In this year's experiment at the Texas A&M University
Agricultural Research and Extension Center at Overton, Evers
will compare three tall fescue varieties with different levels
of summer dormancy.
The three varieties will be an "obligatory" summer-dormant type,
a summer-active type, a highly summer-dormant type and Jesup, a
summer-active tall fescue adapted to the southeastern United
States.
Two lines are of the obligatory summer-dormant variety, one
without endophyte and one with the safe endophyte. Jesup also
has the safe endophyte.
Evers has planted seed of all varieties in pots. These will be
grown outside throughout the late winter and spring. In mid-May,
Evers will move half the plants into a greenhouse. No moisture
will be given to the greenhouse fescues in order to simulate
drought conditions.
"The idea is to see if drought affects their entering dormancy,"
Evers said.
As summer approaches, Evers will move all the plants to growth
chambers, where temperature, light and soil moisture will be
strictly controlled.
The idea is to find out to what degree fluctuating temperature
and moisture affects summer dormancy in all varieties.
"Different growth chamber treatments will determine how
temperature interacts with the various levels of summer dormancy
in tall fescue on starting and maintaining dormancy," he said.
"Placing the pots outside in mid-August under natural day length
and temperature with moisture will determine plant survival from
previous treatments and document the time the various levels of
summer-dormant tall fescue germplasm will break dormancy in
Northeast Texas."
If tests this year and the next show promise, the next step will
be to see how cattle perform grazing tall fescue, Evers said. |