Effects of grazing management on phalaris herbage mass and persistence in summer-dry environments

Abstract

Grazing management strategies that included resting or intensely utilising pasture on a seasonal basis were compared for their effects on phalaris production and plant frequency (persistence). Experiments were established at 4 on-farm sites (Cootamundra ‘old’, Cootamundra ‘new’, Springhurst and Cavendish) in southern New South Wales and Victoria that had previously been sown to phalaris and were grazed by sheep. At each site, 8 core treatments and extra locally determined treatments were initially imposed in 1993–94 on 2 spatial replicates. In order to determine and describe any year of start effects, treatments were applied again in 1994–95 to plots that had been maintained as controls. The phalaris component of the pastures varied from a minor component to the dominant component depending on site (11–54%). Measurements of botanical composition, available herbage and plant frequency were made between September 1993 and September 1996.

Of the core treatments, autumn closure (Cootamundra old and new), winter closure and grazing between defined levels of available herbage (mob stocking) during autumn–winter (Cootamundra old and new, Springhurst), were the most effective in either maintaining or increasing phalaris herbage mass compared to the continually grazed control treatment. In addition, the frequency of phalaris was higher than the control at each of these sites for the autumn–winter mob stocking treatment. These treatments had no effect at the Cavendish site where phalaris was a minor component of the pasture. Rotational grazing, imposed at 2 of the sites (Cavendish and Cootamundra new), led to an increase in phalaris herbage mass compared to continual grazing. A further treatment aimed at encouraging phalaris seedling recruitment by using an extended spring rest until seed fall in summer followed by a rest after the autumn break was imposed at the Cootamundra old site. This treatment increased phalaris herbage mass but did not result in seedling recruitment.

The results emphasise the need for periods of rest when buds are regenerating and tillers developing over the autumn–winter period for phalaris pastures in summer-dry environments.