Effects of stocking rate and closing date on subterranean clover populations and dry matter production in dryland sheep pastures

Abstract

The effect of stocking rate (8.3 [low] and 13.9 [high] ewes+twin lambs/ha) and time of closing in the spring on subterranean clover morphology, phenology, seedling population and the subsequent clover and pasture dry matter production were monitored over 2 years in a cocksfoot-subterranean clover pasture. Mean subterranean clover seedling populations (per m2), measured in autumn 2007, after grazing treatments in the previous spring, were greater (P<0.05) at the low (2850±267) compared with the high (2500±217) stocking rate and with the earlier closing dates (P<0.05) (3850±398, 2950±242, 2100±126 and 1700±152 at 2, 4, 6 and 8 weeks after the first flower, respectively). Seedling populations measured in 2008, after grazing treatments in the second spring, were lower at both stocking rates (1290±89 at low and 1190±70 at high) and at each closing date (1470±84, 1320±84 and 940±66 at 3, 5 and 8 weeks after the first flower, respectively). The effect of stocking rate and closing dates in spring on pasture and clover production in the following autumn was proportional to seedling numbers in both years. Clover production in the following spring was unaffected by stocking rate or closing date in the previous year at the relatively high seedling populations generated by the treatments.