Pasture rotation

This extension
service document is the holy grail of rotational grazing
information for Virginians.  Although the information is geared
toward ruminants like cows and thus will only provide a limited amount
of food for chickens, it answers questions I’ve been pondering all
year, like:

• What can livestock eat on pasture during the summer August slump?
• When is nutritional value of pasture plants highest?
• How long should I leave animals on pasture before rotating them
  out?
• How long should I rest the ground before rotating animals back
  into a used pasture?

I still want to
experiment with chicken-specific plantings and with forest pasture perennials, but it doesn’t
hurt to know the conventional wisdom about rotational pastures before
trying to reinvent the wheel.  Below, I’ve summarized the key
points, but I highly recommend you visit the webpage linked to above if
you want to know more.





Seasonal pastures

A traditional pasture of
perennial grasses and legumes goes through seasonal cycles of forage
abundance.  The specifics of the cycle will depend on your
location and on the types of plants in your pasture, but the chart to
the right should get you started.



You’ll notice that
pasture plants could be divided into three categories — cool season,
warm season, and winter growers.  You may already be familiar with
this distinction if you’ve ever been responsible for choosing the grass
type to seed into a lawn.  Cool season grasses are best suited to
northern locations since they stop growing (and may even die) during
hot, dry summers while warm season grasses are good during southern
summers, but don’t grow much during cold weather.

In Virginia, the top
pasture contenders for each category are as follows:

Cool season — There are three
primary cool season grasses grown in Virginia — tall fescue,
orchardgrass, and bluegrass — along with several legumes — notably
white/ladino clover, red clover, and alfalfa.  Bluegrass has the
thinnest leaves and stems and is probably most palatable to chickens,
but the species will quickly be shaded out of mixed pastures unless
you’re careful to graze the pasture often enough to keep the taller
grasses chomped down.  Fescue is the least tasty cool season
grass, but is the most abundant — if you graze your pastures hard and
continuously, chances are
they’ll turn into stands of fescue.  Mixing in a legume with your
grasses improves the palatability
of the forage while also providing nitrogen for the other plants. 
White dutch or ladino clovers are shallow rooted, so they are easily
stressed by drought, but the plants do well under continous grazing
conditions since their growing tips are protected right at the soil
surface.  I noticed that our chickens prefer red clover, which is
deeper rooted and tends to be more succulent in the summer, but which
will die if grazed too hard.  Alfalfa is similar to red clover in
growth, but is even deeper rooted, so tends to be more productive.

Warm season — In Virginia,
warm season plants can fill in the midsummer slump.  Annuals like
sudangrass, forage sorghum, sorghum x sudangrass hybrids, pearl millet,
foxtail millet, and crabgrass are sometimes grown, but you have fewer
choices if you want to seed your pasture in perennials and forget
it.  Switchgrass, Caucasian bluestem, and bermudagrass are the
only perennial warm season grasses that are typically grown in Virginia
pastures, and even these may die during cold winters.  Bermudagrass is considered
by many to be the most palatable to livestock.  Although most
sources don’t recommend planting Johnsongrass, this plant is a warm
season grass, which explains why my
chickens have been so excited about it during the hot, dry
months.  Finally, you might consider alfalfa.  Although
alfalfa does most of its growing during the spring and fall like cool
season plants, the legume has deep roots that make it less sensitive to
drought, so some fresh growth will come up in the summer.

Winter — For lush winter
pasture in Virginia, you have to depend on annuals, especially
rye.  Perhaps the new research on perennial grains will turn up a
winter pasture plant that you wouldn’t need to seed into bare ground
every year.  Alternatively, you can keep ruminants fed in the
winter by letting portions of your pasture go fallow in August and turn
into standing hay, then turn your livestock in to graze the growth
throughout the winter.  Chickens can’t get much out of hay, so
this technique would need tweaking for the poultry flock.

Rotational grazing times and rest periods

In most cases, rotating
your livestock into and out of pastures by eye works well, but the
extension service did have some useful rules of thumb.  For cool
season plants, you’ll want leave your animals in the pasture for 5 to 7
days, then let the pasture rest 15 days in the spring or 25 to 30 days
in the summer.  Switchgrass should be grazed down to 8 to 10
inches, then rested for 4 weeks.  Caucasian bluestem is similar,
but is grazed lower, down to 3 to 4 inches.  Bermudagrass is
grazed heavily — down to 1 to 2 inches — then rested a mere 2 to 4
weeks until it has 6 to 10 inches of new growth.  Finally, alfalfa
is grazed to three to four inches and then is given three weeks to
recover.



The idea in all of the above
cases is to keep the pasture plants putting out fresh new growth. 
As the drawing to the left shows, grasses and perennial legumes are
most nutritious at the leafy stage.  When the plants are allowed
to turn their energy toward flowering and setting fruit, their protein
and mineral contents drop drastically, replaced by hard-to-digest
compounds like lignin.  (Keep in mind that chickens love grass seeds, so it doesn’t
hurt to sometimes let your grasses go to seed.)





Number of pastures

In Virginia, you need at
least six pastures to ensure optimal pasture health.  Grazing your
animals on a pasture for a week or a bit less will force the livestock
to eat the pasture plants relatively evenly rather than continually
consuming the regrowth of their favorites, which in turn allows those
favorite plants to survive long term.   And, as explained in
the last section, this type of rotation results in tender, delicious
pasture plants when you rotate your animals back in.



During times of low
forage productivity, you may need to add additional pastures. 
These can be pastures that are usually treated as hayfields but are
grazed during the winter or midsummer (a technique that works best for
ruminants.)  Alternatively, you can produce special pastures
formulated to suit the needs of your animals during the summer lull (an
annual pasture of forage sorghum or a perennial pasture of
bermudagrass) or winter slump (annual rye.)





My conclusions

Bits of our pasture are
currently bare, either because the chickens overgrazed those spots or
because we cut down towering weeds that had shaded out the
understory.  It looks like I need to think about diversifying our
pastures by planting some clover, alfalfa, bermudagrass, and
bluegrass.  Meanwhile, it’s been clear for a while that our
growing flock needs more pasture area, so Mark has already started
fencing in two new areas.  It looks like I’ve got a lot more
experimentation to do for the next growing season!