Effect of sowing time on the establishment and early production of tropical and temperate pasture mixtures under irrigation in south-eastern Queensland

Abstract

The most effective time to sow irrigated perennial pastures containing tropical and temperate species was investigated over three years at Gatton, south-eastern Queensland. Three mixtures were sown each month between September and June and in split sowings where the tropical species were sown in September or March, and the temperate species in May. Autumn sowings produced the most seedlings of sown species 40 d after sowing. Of the autumn months, May was the most suitable, with an establishment of 181 plants/m2 and a weed population of only 19 plants/m2. Tropical grass establishment was less than 8 plants/m2 from all sowing times. A considerable proportion of tropical grass sown in autumn appeared in spring. Split sowings were not as effective as autumn sowings and favoured the tropical species, which were sown first. Dry matter yield of sown species in the establishment year varied from 0.9 t/ha for February sowings to 12.0 t/ha for April sowings; weed yields varied from 5.8 t/ha for September sowings to 0.8 t/ha for May sowings. Tropical grass contribution was greatest from the split sowing in which the tropical species were sown in September. Temperate species yields were highest from May sowings. In the second year yields of temperate species declined substantially, mainly because of poor persistence of ryegrass. Although tropical grass yields increased in all treatments, this increase was not sufficient in the autumn sowings to compensate for the low ryegrass yields.