Ranking acidity tolerance and growth potential of Austrodanthonia accessions

Some Australian native perennial grasses that evolved on acidic soils are useful pasture species such as the 25 species of Austrodanthonia. We evaluated the range of acidity tolerance and growth potential in the field of 9 species of Austrodanthonia, comprising 18 accessions collected from southern temperate New South Wales (NSW) as well as the commercial cultivars Taranna and Bunderra. The soil had natural differences in pH in 10 mM calcium chloride (pHCa) and was classified as a brown chromosol to kurosol (yellow/red podsolic). After germination and growth in pots for 9 weeks, seedlings were transplanted into plots with pH differences (mean 4.3 or mean 4.9). Plant growth was scored for 116 days after transplanting and survival monitored for a further 361 days. Visual scoring of plant growth was highly correlated with dry weights (r2 = 0.99). Survival and shoot dry weight were greater at pHCa 4.9 than at pHCa 4.3. For example, survival was 74% at the higher pH and 47% at the lower pH after 116 days and declined very slowly subsequently. Dry weight and survival at pHCa 4.9 were separately and linearly related to dry weight and survival at pHCa 4.3, respectively. Austrodanthonia accessions/cultivars exhibited about a threefold range of acidity tolerance and dry matter production. When acidity tolerance was ranked using either dry weight or survival, the rankings were similar; however, dry weight data had a greater dispersion, thus dry weight may be the more sensitive tolerance index. On the other hand, survival may be the more cost-effective indicator of acidity tolerance. It is likely that tolerance of acidity may be attributed to tolerance of aluminum rather than of the hydrogen ion. Some accessions produced more dry matter, had higher survival and greater acidity tolerance than the commercial cultivars and thus show potential as useful pasture components.