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It should be noted that this model prediction is based on a typical farm in the North Western
Free State, where rainfall variability remains to be a key risk factor (i.e. lower yield assump-
tions for maize and soybeans). With the inclusion of pasture in a cash cropping system (as
in this particular example) at least 25% of the total area planted has a risk mitigating impact.
Management of pasture ley crops before the
successive grain cropping cycle
As part of the proposed pasture ley cropping system, no-till planting of the crop is essential
for reducing the risks of soil erosion. It is beneficial to plant directly into the plant residues,
which consist of pasture material from the ley cropping season/s that has been killed with
herbicide, one or two weeks before planting.
Intervals between the killing of the pasture ley crop and the planting of the successive crop
should be short, otherwise the residues, especially legume residues with their low C:N ra-
tio’s, will decompose very quickly. Grass ley pastures have the added advantage of taking up
N rapidly during the early rains, minimising the leaching loss and then releasing it to the crop
when killed by the herbicide.
Mixed grass and legume pastures are preferred from a grazing perspective compared to pure
monospecific grass pastures. Crops grown after pure grass ley pastures (especially grass
crops such as maize) could have yield restrictions due to an N-negative period and N-fertiliser
levels should be adjusted accordingly (around 30% higher).
To prevent the grass component of the mixed pasture ley crop to dominate, judicious cattle
grazing can be used to remove the larger grass canopy, which will benefit the legume com-
ponent. When grazing ley crops in the dry season (winter), it is essential to leave sufficient
well distributed plant cover on the soil surface for the successful re-establishment of either
the pasture or the successive grain crop.
This is a key compromise that has to be reached between the needs of the animals and of the
plants in the system.
Conclusions
Pastures are most likely to produce good profits compared to grain crops on a per hectare
basis, especially on soils that have accumulated effects of land degradation which will in-
creasingly limit the grain potential in future.
Secondly, pasture leys have significant benefits and improvements to ecosystems (especially
soil health), which are not always quantified to emphasise the dual purpose of the pasture
ley crop. However, the noticeable increases in grain yields after pasture ley crops will
provide some reflection on their additional rand value, other than just the revenue generated
from the pasture ley crop from cattle grazing.
Pasture ley crops improve the productivity and enhance the sustainability of mixed farming
enterprises. For such systems to be effective, it is imperative to conduct ongoing on-farm
research of these complex systems, especially to:
Understand the competition between crops and undersown legumes.
Determine the optimum sowing rates to maximise the subsequent benefit of the ley crop.
Study the seed dynamics of annual legumes.
Study the influence of herbicide residues associated with minimum/zero till cropping
systems, especially on legume pasture ley crop establishment and growth.
Develop management strategies which maintain the pasture ley species, while benefiting
the animal production component of the integrated CA system and not resulting in anti-
quality factors affecting the animal health.
Overall, the positive attributes of an integrated crop- and pasture-based livestock CA system
will facilitate the creation of a more sustainable grain production system.
For more information contact Dr Wayne Truter ( , Mr Gerhard van der
Burgh ( , Dr Hendrik Smith ( or Mr Gerrie
Trytsman ( .
References
Jones, RK, Peake, DC, and McCown, RL. 1983. The effect of various tropical legumes on nitrogen supply. Annual
report 1982 - 1983, division of tropical crops and pastures, CSIRO: Australia. pp. 135 - 136.
Jones, RK, Dalgliesh, NP, Dimes, JP and McCown, RL. 1991. Sustaining multiple production systems 4.
Ley pastures in crop-livestock systems in the semi-arid tropics. Tropical grasslands 25, 189 - 196.
Lloyd, Dl, Smith, KP, Clarkson, NM, Weston EJ and Johnson, B. 1991. Sustaining multiple production systems 3.
Ley pastures in the subtropics. Tropical grasslands 25, 181 - 188.
McCown, RL, Winter, WH, Andrew, MH, Jones, RK and Peake, DC. 1986. A preliminary evaluation of legume ley
farming in the Australian semi-arid tropics. In: Haque, I, Jutzi, S and Neate, PJH (Eds) Potentials of forage leg-
umes in farming systems of Sub-Saharan Africa. pp. 397 - 419. (ILCA: Addis Ababa.)
Wylie, P. 2007. Economics of pastures versus grain or forage crops. Tropical Grasslands 41, 229 - 233.