Tagasaste silvopastures in steep-hill country. 1. Tagasaste edible dry-matter production and nutritive value.

Context: Tagasaste (Cytisus proliferus) has potential to supplement pasture production in steep-hill country and increase pasture resilience. Aims: To (1) quantify production of edible dry matter (EDM) of pruned 2-year-old tagasaste shrubs and branches from unpruned 10-year-old tagasaste trees, and (2) determine the effect of proximity of the 10-year-old tagasaste trees on selected pasture species established as spaced transplants. Methods: A site was established on the eastern coast of the North Island of New Zealand on steep-hill country (>20° slope). Tagasaste and pasture species production was measured over 3 years. Results: Tagasaste shrubs produced an average of 2.7 kg EDM shrub−1 year−1 and a tree branch produced 129 g EDM year−1. The metabolisable energy content of tagasaste branches averaged 10.0 MJ kg EDM−1, the crude protein content ranged from 18% to 27% and neutral detergent fibre content averaged 39%. Branch diameter and length were poor predictors of EDM branch−1. There was no effect of increasing proximity to tagasaste on DM production of the resident pasture. Effects of increasing proximity to tagasaste on the growth and survival of selected pasture species are reported in a companion paper. Conclusions: Edible-DM production was much greater from shrubs than tree branches and it was not possible to predict branch EDM from branch diameter or length. Implications: A tagasaste silvopasture is likely to be more productive if tagasaste is managed for grazing in situ than if using mature trees for harvesting of branches for browse. The production of edible dry matter (EDM) of 2-year-old tagasaste shrubs averaged 2.7 kg shrub−1 year−1 on one steep, north-facing hillside on the eastern coast of New Zealand. This equated to the production of 2.2 t EDM ha−1 year−1 at spacings of 3.5 m (816 shrubs ha−1), with a metabolisable energy content averaging 10.0 MJ kg EDM−1. In low-producing (<4 t DM ha−1 year−1) pastures on drought-prone, steep-hill country, inclusion of tagasaste could increase edible forage production by 50%. [ABSTRACT FROM AUTHOR]