NEWS
Further perspectives and results
on high density rotational grazing
Reprinted From: RPO Newsletter: November 2019 http://bit.ly/2SZDWIB
Heinz H. Meissner
I
have been informed that the results
and debate on this topic have been
keenly followed! Thus, as a follow
up to last month’s contribution, titled:
The grazing management model debate
continues! I have done a further litera-
ture study of comparatively new find-
ings and overviews (see below), and to
give my own perspective on the topic.
In the study by Venter and co-workers
they surveyed 48 farms country-wide
which were under consistent manage-
ment for about 15 years, to test the hy-
pothesis that rotational grazing sustains
higher animal numbers while increasing
grass cover and reducing bare ground
and woody plant cover. In a subset of
the data they compared 23 fence lines
between farm neighbours or camps with
similar fire programs, but with grazing
management varying from continuous
to ultra-high density grazing. They also
did comparisons with satellite-assisted
remotely-sensed vegetation indices.
The results from the 48 farms revealed
that stocking rates on average were
about 59% higher than the recommend-
ed rates and that adherence to high
density rotational grazing management
did not affect this. In the fence-line com-
parisons, the results yielded about a 85%
relative difference in grazing densities
but revealed no significant differences
in vegetation indices, bare ground, and
grass and woody plant cover. The abso-
lute magnitude of fence-line differences
in stocking rate of 30% and grazer per-
centage of 55% also had no consistent
effect on vegetation cover. Thus, this
analysis of the 48 farms country-wide
corroborates findings from many experi-
mental studies on rotational grazing and
adds weight to it by including a diversity
of rotational grazing intensities. The evi-
dence in the study was not compatible
with commonly observed negative ef-
fects of high stocking rates on vegetation
cover, implying that the relatively high
stocking rates were within the carrying
capacity of the farms studied. Further,
the previously untested hypothesis that
rotational grazing alters woody plant
cover was not supported in this study.
The authors concluded that, based on
these and the findings of others, con-
tinued advocacy for extreme forms of
rotational grazing management such
Grassroots
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No 1
as ultra-high density stocking rate is
unfounded.
The next study addressed the question
if heavy grazing and land degradation
have a negative effect on plant diversity
and richness (abundance). The study by
Rutherford and Powrie was undertaken
to determine the effects of heavy grazing
on richness of plant species across the
arid and semi-arid rangeland biomes of
South Africa. These were the Succulent
Karoo, Nama-Karoo, Thicket, Grassland,
Kalahari dune savanna and Mopane sa-
vanna. The related parameters of spe-
cies diversity, evenness and turnover
were also examined.
The impact of heavy grazing on plant
species richness were found to vary from
negligible or slightly positive to distinctly
negative. The sharp reductions in rich-
ness may have been partly associated
with variables other than grazing which
can occur in arid areas. Species diversity
did not always correlate well with spe-
cies richness and was often dominated
by species evenness patterns. Moderate
to substantial turnover of species oc-
curred, even with negligible change in
species richness. Species turnover was
largely associated with replacement of
species. Heavy grazing altered species
composition at all study sites, usually
with reduced grazing quality and favour-
ing annual plants. Surprisingly, however,
few of the replacement species on most
of the study areas were alien or exotic.
The results showed that the question
of whether plant species richness and
diversity is negatively influenced by
heavy grazing depends on area and
biome type.
Finally, in a review by Teague and Barnes
from results obtained mainly in the US,
they concluded that what they referred
to as ‘adaptive multi-paddock (camp)
grazing management’, leading conser-
vation farmers have achieved superior
results with this approach in ecosystem
improvement, productivity, soil carbon
and fertility, water-holding capacity and
profitability. The method is based on
multiple camps per herd with short graz-
ing periods, long recovery periods, and
adaptively changing recovery periods,
residual biomass (left-over material), ani-
mal numbers and other management el-
March 2020
ements as conditions change.
So, then what is my perspective and
recommendations? Experimental re-
sults and farmer reports to date show
both positive and negative effects
with high density rotational grazing,
and also sometimes no differences in
comparison with other grazing man-
agement systems. These effects are
in terms of biomass, species diversity,
ecosystem protection, carbon foot-
print, use of fire, animal productivity,
bush encroachment, animal species,
marketing system and profitability. I
do not find this surprising as biomes
differ as the results above show, and
even districts and farms. There are
simply too many variables to extrapo-
late from one area to the next. Graz-
ing management is a farm and farmer
issue, meaning that a farmer should
do his/her own on-farm trials within
his/her production system and ap-
proach to establish what works with
him/her. High density rotational graz-
ing can be effective, but so can other
systems; the common denominator is
comparatively long resting periods. I
agree with the Teague and Barnes rec-
ommendation of adaptive multi-camp
grazing management; the farmer
adapts his/her number of animals ac-
cording to veld biomass (and other
feed sources available) and shifts the
animals accordingly, based on expe-
rience and analyses by pasture scien-
tists where applicable.
References
Z.S. Venter, M.D. Cramer & H.J. Hawkins,
2019. Rotational grazing management
has little effect on remotely-sensed veg-
etation characteristics across farm fence-
line contrasts. Agriculture, Ecosystems
and Environment 282, 40-48.
M.C. Rutherford & L.W. Powrie, 2013. Im-
pacts of heavy grazing on plant species
richness: A comparison across rangeland
biomes of South Africa. South African
Journal of Botany 87, 146–156.
R. Teague & M. Barnes, 2017. Grazing
management that regenerates ecosys-
tem function and grazing land liveli-
hoods. African Journal of Range & For-
age Science 34, 77–86.
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