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Spring sown sub clover: will it regenerate?

P.M. Evans, B.A. Rowe and J.A. Carpenter

Department of Agriculture, Kings Meadows, Tasmania 7249

Previous studies of flowering times of sub clover showed the early flowering cultivar Trikkala becoming of mid season maturity when sown in autumn in the Tasmanian environment (1). If flowering is retarded by autumn sowing in higher latitudes, then, conversely, it could also be accelerated by sowing in late winter and early spring.

Since it is not uncommon for Tasmanian pastures to be sown in spring there is a need to study the behaviour of sub clover cultivars included in these mixtures.

Methods

Eight commercial sub clovers ranging in maturity from Nungarin to Meteora (Table 1). were sequentially sown in pots at monthly intervals from May to December, thinned to four plants per pot, replicated three times and grown outdoors. Flowering date was recorded when three out of four plants in a pot had at least one inflorescence. Plants were watered as required.

Results and discussion

Time to flower became shorter with each successive sowing up to and including November (Table 1), thereafter taking longer or becoming erratic for all cultivars except the very early ones.

Table 1: Days to flower for sequential sowings of e sub clover cultivars with mean maximum 8 minimum temperatures and corresponding photo-period or each month

d.n.f. = did not flower

*not all Plants flowered

Since mean rainfall in the sub clover growing areas of the State exceeds 50 mm in November and severe water stress does not develop till December or January, early September-sown Nungarin, Dalkeith or Trikkala should normally be able to set seed and regenerate. Nungarin and Dalkeith are too early to be productive in this environment. However, Trikkala regenerating the following autumn will be a very useful mid season cultivar of about the same maturity as Woogenellup. The data suggest these two cultivars have different sensitivities to vernalisation or photoperiod: or differing optimum temperatures for flowering, making them flower 65 days apart when sown in December (Table 1).

It is not possible to separate the effects of photoperiod and temperature on flowering in this uncontrolled environment because they are closely correlated.

1. Evans, P.M., Carpenter. J.A. (1987), Proc. 4th Aust. Agr. Conf. 163.

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