Effects of sunny and shady aspect on pasture yield, digestibility and sheep performance in Canterbury

Abstract

Annual pasture dry matter (DM) production from improved brown-top-dominant hill pastures varied from 3.5 to 7.4 t DM/ha over three years. A south aspect produced on average 14% more dry matter than a north aspect; both had spring and autumn growth peaks, and a summer depression which was greater on the north aspect. A nucleus flock of hoggets was set-stocked on each aspect from October to June and numbers of extra sheep were adjusted monthly if necessary to maintain similar quantities of available herbage on each aspect. Both nucleus flocks generally grew at similar rates so their seasonal growth patterns were similar. In the second and third year those on the south aspect grew 3 to 5% more wool. Net liveweight gain per hectare was greater on the south than the north aspect in the first year owing to a higher seasonal stocking rate on the south aspect, but in two subsequent years production was similar. The digestibility of pasture on offer to stock was 75 to 80% in spring and 45 to 50% in summer. It recovered to 50 to 55% in autumn then deteriorated to 40 to 45% in June. Small differences were measured between aspects.