Comparison of four phalaris cultivars under grazing: drought survival and subsequent performance under rotational grazing versus set stocking

Abstract

Four cultivars of phalaris were evaluated for their ability to survive a severe drought in 1994 in an existing grazing experiment at 2 sites near Canberra. The effect of rotational grazing and set stocking on persistence of phalaris measured as basal cover, pasture composition in spring and animal production from the pastures was assessed over the next 4 years. Basal cover of all cultivars declined sharply in 1994, but had recovered by August 1995 at a site with a relatively deep soil profile. Recovery was slower at a site with a shallower soil profile. Sirosa declined more in basal cover than Holdfast and Australian at the latter site. All of the cultivars survived the drought well but Sirosa may be more sensitive to overgrazing in drought. Compared with set stocking, rotationally grazed pastures had a higher (P<0.001) proportion of phalaris for all cultivars 2 years after management treatments began, and a higher (P<0.005) basal cover for 2 winter-active cultivars after 3 years. Overall, a divergent effect of grazing management on basal cover (management × year interaction) could only be demonstrated at P = 0.08 because of a large effect of site variation for another winter-active cultivar, Sirosa. Phalaris basal cover did not decline with set stocking and it was concluded that rotational grazing was beneficial, but not crucial, for the persistence of winter-active phalaris cultivars in this environment. Site factors and their manipulation by management were also important for the persistence of phalaris. A review of the persistence of phalaris over the entire 9 years of the grazing experiment concluded that all cultivars displayed good persistence under conditions of reasonable soil fertility. The importance of good establishment for a high presence of phalaris in later years was emphasised.