Previous PageTable Of ContentsNext Page

The persistence of phalaris under grazing

R.A. Culvenor and R.N. Oram

CSIRO Division of Plant Industry, GPO Box 1600, Canberra ACT 2601

The breeding of P halaris aquatica L. (phalaris) has led to improved seedling vigour, winter growth, seed yield and drought avoidance compared with the original cultivar, Australian. However, there have been reports that the persistence of the bred cultivars is poorer than that of cv. Australian. This difference in persistence is thought to be in response to grazing, particularly during spring, although interactions are likely with the increasing acidity of soils into which these cultivars are now sown. This paper reports a preliminary examination of variation in persistence under grazing and correlations with some vegetative characters of spaced plants.


Persistence was measured as basal cover on intermittently grazed swards of 83 half-sib families and several cultivars sown in 1987 on limed soil at Canberra. Basal cover was estimated in 1990 and 1991 by counting the proportion of hits on live base by a set of 10 pins placed at random until at least 20 hits on live base were made. The swards were subjected to heavy continuous grazing (up to 32 sheep/ha in spring) during 1990. Spreading ability (area of base), winter growth (score 1-7) and tiller density (score 1-9) were assessed on spaced plants of the same lines in 1990-91.

Results and discussion

Basal cover values for 1990 were correlated with density estimates made in the first year (r=0.52, P<0.01). The values for 1990 therefore reflect both early establishment as well as persistence. Australian was superior in ground cover and persistence to all other cultivars and families (Table 1). Compared with cv. Australian, spaced plants of the bred cultivars and most of the half-sib families were less spreading, less densely tillered and more winter active. Sirosa and Seedmaster displayed the largest decline in cover after a year of heavy continuous grazing. Basal cover in 1990 was significantly correlated (P<0.01) with the tiller density (r=0.60) and spread (r=0.36) of spaced plants. In a multiple regression, 41% of variation in 1990 sward basal cover was accounted for by these two spaced plant characters. The higher correlation with tiller density is possibly also due to further correlations between dense tillering and other characters such as shortness and prostrateness which also confer resistance to grazing damage.

Narrow-sense heritabilities among the half-sib families were moderately high for tiller density (0.45) but low for spread of spaced plants (0.10). The rhizomatous spread of phalaris plants is thought to be important for persistence by conferring the ability to recolonize space in pastures after damage. The low heritability of this character would make improvement by selection difficult. Should further research demonstrate the value of rhizomatous spread, substantial improvement might be found in a P. aquatica x P . arundinacea population under development.

Previous PageTop Of PageNext Page