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.

Effects of grazing management on Sirosa phalaris herbage mass and persistence in a predominantly summer rainfall environment

“…Preliminary results (Harris and Ayres 1997), at a high elevation site on the Northern Tablelands of New South Wales, showed good persistence of Australian phalaris under continuous grazing, despite severe drought in 1994-95. In contrast to the present experiments, similar studies in a southern, winter rainfall zone Virgona et al (2000) found that at 3 of the 4 sites studied, autumn-winter, rather than autumn-spring management was important for phalaris persistence.…”

“…Fertilised swards of Sirosa phalaris sown with a companion legume were studied at 3 sites on the North-West Slopes. Results of comparable TPSKP grazing management studies on Sirosa phalaris in predominantly winter rainfall zones of south-east Australia were reported by Virgona et al (2000).…”

Interaction of plant genotype and management in the persistence of a perennial grass exposed to grazing and soil fertility stresses

“…If Holdfast GT survives equally as well as Australian, this experiment demonstrated it has production advantages in winter when feed is usually in short supply. If pastures can be managed through long‐term adherence to rotational stocking, destocking under very adverse conditions or tactical rests (Virgona et al ., ), then the winter‐active cultivars other than Holdfast GT (Holdfast, Sirosa, Landmaster, Advanced AT, Atlas PG) remain an equally or more productive option, and more productive in winter than Australian, and some will be preferable in moderately–strongly acidic soils (Advanced AT, Landmaster). Soil fertility strongly affected the ability of the phalaris stands to recover their basal frequency by vegetative expansion after the early decline due to overgrazing during drought.…”

“…Although rotationally stocked plots in this study were grazed to low residual mass in each grazing cycle, the high herbage mass achieved during the rest period clearly benefitted survival due probably to factors such as the development of larger phalaris plants, deeper roots and higher carbohydrate levels. These results confirm other reports of benefits from rotational stocking on phalaris composition and herbage mass (Virgona et al ., ; Warn and McLarty, ; Chapman et al ., ) and basal frequency (Culvenor, ). Studies have shown that tactical rests particularly in the autumn–winter winter period can also be effective in maintaining phalaris composition (Virgona et al ., ) and that flexibility in grazing interval is required to cope with varying seasonal conditions (Virgona and Bowcher, ).…”

Does greater night‐time, rather than constant, warming alter growth of managed pasture under under ambient and elevated atmospheric CO2?

“…Compared with normal Phalaris‐ based pasture systems that are subjected to periods of drought and where the main source of nitrogen is through symbiotic nitrogen fixation by clover, this experiment features a very high production rate. Virgona et al . (2000) reported spring pasture growth rates of up to 10 g/m 2 d −1 while Lolicato (2000) reported maximum spring growth rates of 15 g/m 2 d −1 for hybrid Phalaris.…”