Herbage production and seed yield of defoliated subterranean clover swards in a cool temperate environment

Abstract

Seasonal growth patterns were determined for defoliated swards of three mid-season subterranean clover cultivars (Seaton Park, Woogenellup and Mount Barker) and one early-flowering cultivar (Nungarin) established at three times of the year (early March, mid-April, late May) in a cool tableland environment. The time of sowing significantly affected the autumn, winter, spring, and total herbage production of all cultivars. Swards sown in early March showed an autumn and spring peak in herbage with a depression in winter. Swards sown in mid-April or late May produced very little herbage in autumn and winter. Total herbage production ranged from 10.3 t/ha from a mid-season cultivar sown in early March to 3 . 2 t/ha from an early maturing cultivar sown in late May. Total herbage production of the mid-season cultivars was not related to maturity rating. However, the early maturing cultivar, Nungarin, produced considerably (46-65%) less herbage than the mid-season cultivars. Its productivity was also the most sensitive to a delayed start to the growing season. The interval between sowing and flowering was shortened by later sowing, later maturing cultivars showing the greatest decrease. Seed yields ranged from 290 kg/ha for a Mount Barker sward (sown in late May) to 1203 kg/ha for a Seaton Park sward. On average, Seaton Park and Nungarin produced the highest seed yields, a result of setting more seed but not larger seed. Woogenellup set significantly larger seed than the other cultivars. Earlier maturing cultivars had the highest seed yields and appeared relatively insensitive to low temperatures during flowering. It was concluded that the use of early maturing cultivars in this environment could substantially reduce potential pasture production. Seaton Park was considered to be the most suitable cultivar, combining a high seed yield with good herbage production.