The Rural Voice, 2006-04, Page 18Turning sunlight into meat
If you think of a pasture as a giant solar panel
powering gour livestock enterprise gour management
will change, sags grazing expert Jim Gerrish
Story and photo by Keith Roulston
It is the oldest tool in the toolbox
of livestock fanners but when Jim
Gerrish talks about it, pasturing
takes on a space-age connotation.
For Gerrish, a Idaho -based
grazing specialist formerly with the
University of Missouri, a pasture is a
gigantic solar collector and
improving pasture management is all
about "building a better solar panel".
"If you think of every acre you
manage as a 43,560 -square -foot solar
panel, you easily begin to see how to
improve your operation," he told
graziers attending the 2006 Profitable
Pastures conference in Elmwood,
March 8.
To build a better solar panel of
your pasture, the key is maximizing
photosynthesis, Gerrish bxplained.
"Bare soil does not capture solar
energy. Dead, brown plants do not
,capture solar energy. Only green,
growing leaves take solar energy and
make it into livestock feed."
So pasture management becomes
about creating the conditions for
maximum collection of solar energy.
"An excellent pasture should have at
least 90 per cent of the ground
covered with green, growing plants."
Despite the fact most people agree
on the importance of proper pasture
management, their practice falls
down badly. "In most of North
14 THE RURAL VOICE
America I believe farmers and
ranchers lose up to 50 per cent of
their production potential due to
grazing (pasture) too short and not
providing adequate rest periods for
plants to recover," Gerrish said. "The
key principle is it takes grass to grow
grass!"
Over the length of the grazing
season you should be able to have
your animals harvest 70-80 per cent
of the growth on your pasture field,
Gerrish says. By comparison, a
continuously -grazed pasture typically
sees animals harvest 30-50 per cent
of the forage produced. In the most
intensively managed pastures, he has
seen that figure hit 90 per cent of the
forage produced. "That's better than
cutting and chopping without the
expense."
The solar panel depends on
leaves, so you won't take advantage
of the available sunlight if the plants
are too short or too tall.
If you have a healthy pasture to
start with, the key to productivity is
residual management: it's not how
much growth there is when you turn
your cattle or sheep into a paddock,
it's how much is left when you move
the animals on to the next fresh
pasture.
While good management might
allow you to harvest up to 90 per cent
of the crop throughout the grazing
season, you want to only harvest 50-
60 per cent of what is growing during
each rotation of the pasture.
Leaving a good amount of
residual plant behind means more
leaves to capture more sunlight and
grow faster, he said. .
Using slides Gerrish demonstrated
the three phases of pasture
development. A phase one pasture
has too little leaf cover and perhaps
only captures 20 per cent of
radiation. This pasture is, however,
made up of the newest, youngest and
highest -quality leaves.
Phase two pastures are the ideal
solar collector making use of 60-70
per cent of solar radiation. "Ideally
you always want your pasture in
phase two," Gerrish said. This can be
accomplished by putting your
livestock into the pasture at "high"
phase two and taking them out at
"low" phase two.
Phase three pasture is too tall
with too much shading .and too
many dying leaves. This is hay.
If you take your livestock out
while the pasture is in low phase two,
it will probably need only a 30 -day
rest and regrowth period. That means
on a 180 -day grazing season, you'll
get six harvests off that paddock.
Continued on page 16