Discipline: pastures; Keywords: kikuyu-ryegrass pastures, stocking rates, weedy species, Plantain, clover, Lucerne, Tall Fescue, monoculture, mixed species.
Kikuyu-ryegrass may no longer be optimum in the south-eastern Cape because of a number of reasons:
• Extended periods of lower than expected rainfall
• Poor persistence of ryegrass, with a decline of as much as 44% reported in even the most productive ryegrass cultivars from year one to year two
• Although kikuyu can support high stocking rates, is high yielding during summer and has resulted in an improvement in soil C levels in the southern Cape, it requires high nitrogen fertilisation rates to remain productive, has low winter yields and its low forage quality tends to limit milk yield per animal
• Research on kikuyu-ryegrass pastures under more than 15 years of no-till management indicated that pastures often contain in excess of 60% of weedy volunteer grasses such as Paspalum urvillei, Digitaria sanguinalis, Eragrostis plana and Sporobolus africanus during summer/autumn
• Increasing fertiliser costs have resulted in producers reducing fertiliser inputs. The impact of these strategies on the long term pasture yield, persistence of sown pasture species and nutrient use efficiency are not sure.
The best forage based approach to address issues relating to low resource use efficiency, poor persistence over years and low resilience under adverse climatic conditions of pasture systems in the southern Cape, is to introduce alternative or novel pasture species. The inclusion of forage herbs, such as Plantain (Plantago lanceolata), into pastures has been reported to hold various potential advantages:
• an improvement or maintenance of milk yield compared to ryegrass during adverse climatic conditions,
• higher kg milk solids production per animal,
• lowered rates of N leaching,
• improved dry matter intake in animals,
• higher forage quality compared to perennial ryegrass-clover pastures,
• higher summer/autumn production than temperate grasses,
• a lower decline in plant population over years compared to ryegrass, and
• more resilience to periods of drought.
With this in mind, a farmlet study was conducted on the Outeniqua Research Farm over three years to determine the whole system production potential of four pasture systems based on the traditional system (Kikuyu-ryegrass), monocultures of alternative species (Tall fescue and plantain) and two pasture mixture that included alternative species (Tall fescue, plantain and red clover; ryegrass, Lucerne, chicory and plantain).
The results are preliminary, but do indicate that the inclusion of plantain, chicory, lucerne and Tall Fescue, whether in a mixture or as a monoculture, holds the potential to yield similar or even higher pasture and milk per ha when compared to kikuyu-ryegrass. The inclusion of forage herbs and legumes in pasture mixtures, in particular, could improve milk yield per cow from spring to autumn.
The establishment of alternative pasture species and mixes can also be an effective method to manage weed ingression in minimum till pasture systems in the south-eastern Cape. The inclusion of herbs, following eradication of the existing sward by herbicides, can reduce the weedy grass component in the pastures. Another strategy would be to utilise herb monocultures on areas where weedy grasses are problematic, as it can allow the use of grass-specific herbicides. The competitive yielding ability of Tall fescue pasture in the monoculture system, particularly during summer and autumn, illustrates that it, rather than a ryegrass monoculture, could also be established in areas where broadleaf weeds need to be controlled.
However, a major challenge to the adoption of mixtures into pasture systems, is the management of botanical composition due to the complexities in determining what species and/or mixture to plant and when renovation or re-establishment is required. This will require further and more detailed research to allow for more effective recommendations to be made. Here the major determinants will firstly be the properties of the area to be planted in terms of climate, soil properties and available resources (for example irrigation water supply). The second will be the motivation for the inclusion of a specific component for example: rapid establishment (ryegrass and clovers), versus persistence (fescue and Lucerne). Lastly, interspecies competition and complementarity, particularly during establishment, needs to be taken into consideration, for example including a highly competitive component like ryegrass at a high rate (ryegrass) may reduce the contribution of a more persistent and environmentally resilient species like plantain.
Van der Colf, J., Ammann, S.B. & Meeske, R., 2022. Forage herbs and mixtures: paradigm shift? In: Proceedings of the South African Large Herds Conference, Champagne Sports Resort, 6 – 8 June 2022.