93
March 2014
qualities will essentially determine to a large extent the forage
quality and anti-qualities components expected of the species.
Management and utilisation
To optimally utilise the benefits of a pasture crop, both in the context
of contributing to soil health and secondarily the provision of
grazing or fodder, the correct establishment, fertilisation, irrigation
and weed control practices are instrumental. In this series we
will highlight the most important aspects with respect to these
management practices for the most common and recommended
pasture species.
Once the pasture has been successfully established, the utilisation
of the pasture needs to be conducted in such a way that it stimulates
the growth of the pasture species, rather than restricting its growth
through over-utilisation and consequently damaging the growth
points.
The correct stocking rates will play an empirical role in the utilisation
of the pasture. These stocking rates will ultimately establish the
grazing system required to optimally utilise the pasture and achieve
maximum livestock production from the area. The time at which
different pastures are to be utilised, will also be highlighted in this
series, as this aspect will be used to select the correct pasture crop
in rotation and/or for soil conservation strategies.
Management challenges
Some pasture crops are not always the easiest species to establish
and in some cases to manage. Nutrient and water management of
pasture species can become challenging, especially if an intensive
grazing management system is implemented. Often pasture crops
fall victim to pest infestations and require some form of management
change together with intensive treatment to overcome the situation
to heal the pasture crop.
Many times certain uncontrollable environmental conditions can
bring upon certain anti-quality factors which a land user needs to
be aware of, as this can be detrimental to the livestock herd’s health
and production potential. There often exists situations where fire
can have severe effects on the regrowth rate of certain species,
and specific management inputs will be required to support such
a pasture crop, to achieve its full growth potential at a later stage.
Soil conservation and health benefits
Primarily pastures are planted to produce grazing or fodder, however
in integrated CA cropping systems, the main contribution of the
pasture should be to conserve and heal the soil for sustainable and
profitable crop production.
Many pasture species can fulfil these requirements since most of
the species are perennial and have remarkable root systems which
facilitate soil health recovery. Very important benefits which pasture
crops accentuate include:
Improving nitrogen for subsequent crops (with legumes)
Rebuilding soil organic matter and improving soil structure
The control and management of weeds
Providing a disease and pest break
Reducing runoff, soil erosion and deep drainage.
It is however an opportunity for land users to utilise these
pasture crops at the same time as this utilisation stimulates both
above-ground (stem and leaf) and below-ground (root) growth.
The secondary benefit of pasture utilisation by livestock, is the
importation of nutrients, microbes and additional organic matter
through urine and dung. It is also quite common that intensively
cultivated soils planted to pasture ley crops experience a degree of
surface compaction/crusting in the first year or two depending on
the soil type. This surface compaction/crusting can lead to erosion
if excessive thunderstorms are experienced, however as a result of
hoof impact of grazing animals the surface crust is disturbed and
can facilitate better moisture infiltration. In addition to this, plant litter
is also trampled into the soil assisting with the decomposition of the
material which then contributes to the soil organic matter cycle.
Animal production aspects
Since crop land is being rested or conditioned for future grain crop
use (within a long term and diverse CA crop rotation system), the
period which these areas are withdrawn from grain production,
provide the opportunity to dual purposefully heal (rehabilitate) the
soil and utilise the pasture crop simultaneously.
Livestock are the key factor to facilitate and accelerate the
aforementioned approach in a profitable manner. Grain producers
often have the added advantage of crop residues which can
add significant value to a fodder flow programme for a livestock
enterprise. It is however imperative that the pasture crops should
be managed to achieve good livestock production per hectare
rather than production per animal.
Specific pasture crop types and benefits
When selecting a pasture crop to be included into a grain cropping
system to support CA principles, it is essential that the pasture
crop is selected with a clear understanding of its management
requirements and challenges.
Pasture crops vary from warm season and cool season types, they
include leguminous crops for biological nitrogen fixation, which
consequently result in these pasture crops having a higher forage
quality. Certain pasture crops have a higher requirement for water
and nutrients and others are more tolerant of poor sandy soils and
drier conditions.
Some species are more tolerant of acidic soils and others more
tolerant of brackish soils. Winter versus summer seasons provide
different challenges, therefore the appropriate selection of a pasture
crop to be integrated into a cropping system will depend on the need
of the land user.
Conclusion
Integrated crop and pasture-based livestock production systems
have enormous potential to support and enhance the principles of
CA. If these CA-based crop-pasture rotation systems are designed
and implemented appropriately, degraded cultivated soils will
recover and improve, providing the critical basis for sustainable
crop-livestock intensification.
For more information, contact Dr Wayne Truter at
wayne.truter@
up.ac.za
, Prof Chris Dannhauser at
Dr Hendrik Smith at
or Mr Gerrie
Trytsman at
SA Grain/
Sasol Nitro photo competition
– Amanda van Blerk 2013
Currently, most traditional agricultural practices lead to severe land degradation. This situation forces land users to consider more sustainable land
use options, such as conservation agriculture.This series of articles to follow in the coming months will highlight some of the pasture crop species
that can play an imperative role in CA-based crop-pasture rotations.
