|
The period of time a pasture is
allowed to grow or rest between successive grazings is referred to as the
rotation length or rest period. The rotation length serves as the primary
control over the frequency at which a pasture is grazed. Although there are no
ideal rotation lengths, they should be long enough to allow plants to achieve
their maximum rates of growth, but not so long that pastures become so tall and
rank that quality is reduced or that unnecessary forage losses are incurred
through increased amounts of livestock rejection, trampling, and fouling with
manure and urine.
 The information presented in Fig 4 demonstrates the general relationship between forage quality, yield,
and rotation length, and provides practical guidelines for determining rotation
lengths.
During the spring of the year, the
predominantly orchard grass pastures at Cornell grow at a rate of approximately
100 lb/DM/Acre/Day. After a 15 to 20 day growth interval (rotation length), the
forage height will reach approximately 8 to 10 inches and contain between 1200
and 2000 lb of DM/Acre available for grazing above a two inch residual stubble
height. However, during the summer and early fall months, growth rates average
approximately one-half of those observed during spring. As a result, it
requires between 30 and 40 days of growth to accumulate a similar amount of
forage during this time period.
Based on this information, as well
as that obtained from actual on-farm experiences, it is recommended that spring
rotation lengths be planned for around 15 days extending to 30 days by
midsummer, and near 40 days for late fall conditions.
Forage growth rates do not change
abruptly, but gradually, and therefore there are transition periods. During
these periods, rotation lengths must be adjusted accordingly. As spring turns
to summer, there is a transition from faster to slower growth. As a result,
although a rotation length of 15 days may be appropriate the first two times a
paddock is grazed, by the third grazing, 18 to 20 days may be required, and
during the remainder of the summer, perhaps 25 to 30 days. However, as summer
turns to fall, growth rates generally increase until the lack of sunlight and
onset of cold weather slows them back down. As a result, fall rotation lengths
may need to be first decreased by a few days, and then increased to 30 or more
days for late fall conditions.
 Fig 5 represents typical rotation lengths that might be encountered at different
times of the year with cool-season forages.
Keep in mind that the 15 day
spring and 30 day summer rotation lengths are merely guidelines used for
planning purposes. In practice, actual rotation lengths will be based on how
fast or slow the forage is growing and may vary between 12 and 42 days.
|
