The effect of improved aluminium tolerance on establishment of the perennial grass, phalaris, on strongly acid soils in the field and its relation to seasonal rainfall

We examined the hypothesis that the higher aluminium (Al) tolerance of recent cultivars of the perennial grass, phalaris (Phalaris aquatica L.), improved establishment on strongly acid soils and that expression of this tolerance depended on seasonal rainfall conditions. Establishment under a range of conditions by a new cultivar (Advanced AT) with the highest Al tolerance yet achieved was compared with another relatively tolerant cultivar (Landmaster) and less tolerant cultivars and some alternative species on strongly acidic soils by sowing twice per year at six sites over 3 years (2004-06). Seedlings were considered established if they survived the first summer as shown by frequency and yield in the year after sowing. Low autumn rainfall in all years hindered weed control and delayed sowing. Under adequate rainfall in 2004 and 2005 sowings, Advanced AT and Landmaster established similarly and were denser and more productive, on average, than Holdfast and Sirosa, which in turn were higher than Australian II, an order related to Al tolerance measured in solution. Persistence in later years was ranked similarly. Under very adverse spring drought conditions in 2006, Advanced AT established better than Landmaster at the most acidic sites as hypothesised. Soil pH of sites where Advanced AT established better than Landmaster in 2006-07 was <4.2 in CaCl(2). The results suggested that current recommendations on the tolerance of phalaris to acid soils are too conservative and that phalaris is more suitable for acid soils in southern Australia than these recommendations indicate.