28 / 112
Oktober 2016
26
FOCUS
Animals
Special
It can be accepted that with more intensive management higher
levels of commitment, organisational skills, knowledge and infra-
structure are required, which may not always be readily available.
The biggest challenge for implementing this grazing strategy with-
in an existing arable system is the lack of infrastructure, such as
(electric) fencing and watering points.
It is important to understand the reasoning behind ultra-high stock
density grazing and why strict control is required. If livestock are
given too much option of selection during grazing, the animals will
selectively and repeatedly consume preferred plants and patches
of vegetation. Very often overgrazing occurs, especially when indi-
vidual plants are subjected to multiple and severe defoliations with-
out sufficient recovery time. This often results in excessive amounts
of biomass and litter removal, causing soil exposure and degrada-
tion in heavily grazed areas.
Ultra-high stock density grazing in a crop-livestock operation is
ideally achieved by growing a wide variety of crops from all four
crop types (warm and cool season broadleaves and grasses), which
include cash crops (e.g. maize), as well as annual and perennial
ley crops (a range of crops and systems have been introduced
through a series of 26 articles in
SA Graan/Grain
during 2014, 2015
and 2016 [Truter
et al
., 2014, 2015, 2016]).
According to Lund (2015), these types of plants are called ‘super
plants’. Such a highly diverse cropping strategy should keep living
roots in the soil as long as possible. This takes the benefits to an
even higher level, implying that the harvesting of sunlight for grow-
ing crops and building soils is optimised. Soil health and function
are therefore continuously (in a cycle) impacted by root exudates
feeding soil microbes, which in return provides vital mineral nutri-
ents for the plants.
By mixing crops, the resultant root exudates from the root mass
feed a myriad different species of soil organisms, each adding their
individual qualities to the overall soil health. For example, these
root exudates are also the building blocks for soil aggregates, creat-
ing pore spaces that allow water to infiltrate and store in the soil
profile; they also break disease cycles and reduce pest levels.
A long recovery time between grazing allows the plant to establish a
healthy root system. Carbohydrates are stored in roots and provide
the energy for regrowth post-grazing. A correct stock density will
allow up to 50% of the plant being trampled to the ground by
grazing animals. Animals eat the most nutritious lush tops of the
plant and the energy rich seeds, while the lower stems are trampled
into the soil.
Soil property benefits
When utilising the ultra-high stock density grazing system, it is
essential to keep the CA principles in mind to manage for soil health.
These include:
Permanent organic soil cover to minimise bare ground.
Increase plant diversity of all crop types, warm and cool season
grasses and forbs.
Keeping living roots in the soil all year round.
Integrate livestock grazing.
The simultaneous application of these principles could fairly rap-
idly lead to an increase in soil organic matter, the key element that
Ultra-high stock density grazing systems
3
4