Overton, Texas
August 22, 2008
Forage legumes can provide
livestock producers some relief from the skyrocketing cost of
applying nitrogen fertilizer to their pastures, said a
Texas AgriLife
Research scientist.
But there is a lot of "hype" surrounding forage legumes such as
crimson or arrowleaf clovers, said Dr. Ray Smith, AgriLife
Research legume breeder based in Overton.
"They're not a ‘get-out-of-jail card.’ They're not a silver
bullet, but they do offer some valuable alternatives to
high-cost nitrogen," Smith said.
Smith has long advocated the use of clover and ryegrass winter
pastures to offset winter feeding costs and supply nitrogen for
warm-season grasses.
Given enough moisture, it has always been an economically sound
investment for cow/calf and stocker operations, he said. Now,
with nitrogen costing 80 cents per pound, it has become not just
an option but a necessity so East Texas forage-based cattle
operations can remain profitable.
"A healthy stand of arrowleaf or crimson clover over-seeded on
warm-season perennial grass pasture in East Texas will provide a
nitrogen input of up to 100 pounds of nitrogen per acre per
year," Smith said. "However, this is only accomplished through a
grazing system with the recycling of animal waste. You've got to
be thinking in terms of (recycling through) animal grazing."
About 80 percent of the Earth's atmosphere is nitrogen gas, but
it's not in a form plants can use. However, forage legumes such
as clovers have a symbiotic relationship with rhizobium bacteria
that live in small nodules on the plant's roots, Smith said.
They take nitrogen gas in the air and convert it into a form of
nitrogen that plants can use.
The nitrogen-fixing abilities of legumes is a fact, Smith said,
but many myths persist about the practice.
For example, one piece of misinformation that continues to
circulate is that if one grows clover with ryegrass then no
applied nitrogen will be needed for the ryegrass.
"Wrong!" Smith said. "Clover will not directly provide nitrogen
for the ryegrass in a ryegrass-clover mixture. It will provide
nitrogen to the warm-season grass (that comes later) through
recycling."
Also, the amount of nitrogen fixed from the air by legumes is
dependent upon the amount of nitrogen already in the soil. It is
common practice to plant a clover-ryegrass mix to extend the
winter grazing period, Smith said. However, ryegrass needs
nitrogen before the clover can provide it. The problem can be
solved by correct timing of a nitrogen application. "The
clover-rhizobium symbiosis is regulated by the amount of
nitrogen available in the soil," Smith said. "The sandy, acid
soils of East Texas are low in soil nitrogen, but soil nitrogen
increases if nitrogen fertilizer is applied. If a
clover-ryegrass mix is planted and fertilized, then the
nitrogen-fixation process will be slowed or turned off. The
ryegrass will do great, but the clover will not contribute very
much to the mix."
Smith said the solution is to not apply nitrogen fertilizer at
planting. These mixtures of clover and ryegrass are generally
planted in October. "This will give the early advantage to the
clover, which will start fixing nitrogen," he said. "A low rate
of N -- 50 to 60 pounds per acre – can be applied to the
clover-ryegrass mix in late December or January. This will
increase the ryegrass growth and allow the mix to efficiently
fix and use nitrogen."
Another myth, Smith said, is that clovers can cause animal
health problems, but this is also erroneous. There are no
animal-health problems associated with clovers grown in East
Texas, except for some problems with bloat, which can be easily
managed.
"Bloat can be a problem, but it is not limited to clovers,"
Smith said. "Any fast-growing cool-season forage – ryegrass,
wheat, clover – can cause bloat."
It's easy to prevent bloat, he said. Don't turn hungry cattle
into lush pastures. Feed hay with winter pastures, and put out
anti-bloat blocks.
Bigger issues that face producers this year are seed, fertilizer
and other production costs, Smith said.
Seed costs for ryegrass and clovers are going up for the same
reason as other agricultural commodities: fertilizer, fuel, and
the attraction of growing other more lucrative crops, such as
wheat, Smith said.
Fall seed costs for clover will range from $14/acre for white
clover to $22/acre for Apache arrowleaf clover to $44/acre for
crimson clover. More seed cost information can be found at
http://aggieclover.tamu.edu . |
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