Persistence and tolerance to soil acidity of phalaris and cocksfoot in north-eastern Victoria

Abstract

Persistence of Phalaris aquatica L. cv. Sirosa (phalaris) and Dactylis glomerata cv. Porto (cocksfoot) was evaluated for 5 pH treatments at 2 field sites on acidic soils. At one site (Beechworth) the soil was strongly acidic [pH(CaCl2) 14.21 to depth (80 cm) and contained concentrations of CaCl2-extractable aluminium (Al) >11 ¦g/g. At the other site (Lake Rowan) the soil pH (0-10 cm) was 5.0 and A1 concentrations were 4 ¦g/g. At Beechworth, lime incorporated at 5.5 t/ha improved establishment of phalaris but plant density declined, and by 30 months after sowing, phalaris plant densities were similar to treatments receiving no lime. Establishment of cocksfoot was less affected by lime application than phalaris, and plant densities were similar to those of phalaris by 26 months after sowing. However, there were no differences between pasture species where no lime was applied. Considerable re-establishment of cocksfoot seedlings occurred regardless of soil treatment. Despite the reported relative sensitivity of phalaris to Al in solution culture experiments, at Beechworth phalaris had more root development at depth than cocksfoot or annual pasture. Although concentrations of Al in the subsoil were high, the perennial deep root system of phalaris may give it an advantage over cocksfoot in terms of survival over summer. A larger root system at depth may give phalaris greater potential than cocksfoot for reducing nitrate leaching and soil acidification. On less acidic soils at the Lake Rowan site, lime application did not affect establishment of either phalaris or cocksfoot. Phalaris had greater persistence than cocksfoot at Lake Rowan. Dry summer conditions at Lake Rowan were the likely cause of poor persistence of cocksfoot. More drought-tolerant cocksfoot cultivars are required if this species is to be a useful perennial grass for pastures in ley cropping areas of Victoria and southern New South Wales.