Effects of simulated defoliation on the productivity and resilience of pasture legumes
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Effects of simulated defoliation on the productivity and resilience of pasture legumes
Lead organisation: University of Adelaide
Project Category: Hub Projects
Project summary: 

This project builds on the work of the larger Pasture Optimisation for Drought Solutions (PODS) project, taking measurements from three small plot trials across the PODS project areas, and managing a simulated defoliation trial in the Barossa/Adelaide Hills region.

The PODS project demonstrates pasture management options to deliver enhanced drought resilience by using better-adapted pasture species and mixtures and by implementing best-practice technologies in pasture establishment and management in ley farming systems (where legume pastures such as annual medics or subclovers are grown in rotation with grain crops). Natural capital is increased by extending the pasture growing season and increasing the ground cover of pastures to protect soils for more of the year.

Primarily funded by a Future Drought Fund Soils and Landscapes Grant, PODS focuses on medium- to high-rainfall areas of South Australia, with key locations in the Upper Eyre Peninsula, Murray Mallee, and Barossa/Adelaide Hills. The SA Drought Hub is supporting an additional focus on nutritional benefits to livestock.

Livestock production potential is determined by the quantity and quality of pasture on offer. This project allows us to model what livestock production is possible during pasture establishment and quantify how grazing compromises seed set and long-term persistence. It will also allow us to determine if alternative pasture species can achieve high livestock performance compared to conventional management in low- and medium-rainfall regions.


  1. Determine the effect of simulated grazing (mowing) on biomass production, quality and seed set in the establishment year.
  2. Determine the effect of height and frequency of grazing (mowing) on biomass production and quality of simulated regenerating pasture legumes.

Project description: 

Southern Australia has a long history of sowing annual pasture legume species that increase pasture production and livestock production, and – in the mixed farming areas – the yield of subsequent grain crops.

Subterranean clover and annual medics have a long history of being sown over large areas. In the last 30 years, a range of alternative annual legume species have been developed with some now widely grown. However, farmers in some areas have little or no experience with the alternative species, which have a range of traits that have the potential to lift production, increasing levels of hard seed and therefore aiding persistence through drought.

The grazing trial is held in the Adelaide Hills, which has relatively high rainfall compared to the other trial sites, with many farms focused on high livestock production with animals grazing permanent pastures or fodder crops. Subterranean clover is the pasture legume most widely grown and is highly tolerant of being closely grazed.

Pasture quality is highest when plants are in the vegetative stage, and progressively declines as the plants move into the reproductive phase and senescence. Pasture quality can vary between species at both the vegetative phase and the reproductive phase. The height to which species are grazed and the time interval between grazing can affect pasture quality and total biomass production.

Previous work on grazing practices focused on grasses and pasture legumes common to high-rainfall areas, or combinations of these plant types. Limited research has been performed on the effects of grazing management on production and quality of alternative legume species, especially in drier growing conditions.

This project includes experiments that quantify performance of pastures during the establishment phase in response to defoliation. We will also impose two cutting heights at two cutting frequencies on a range of annual legume species and cultivars. The project will investigate whether species perform differently in terms of dry matter production and quality based on the cutting treatments.