Tagasaste silvopastures in steep-hill country. 2. Effect of increasing proximity to tagasaste on growth and survival of companion pasture species

Context: Tagasaste (Cytisus proliferus), a fast-growing leguminous tree, has potential to supplement pasture production in steep-hill country and to increase pasture resilience.

Aims: In the companion paper, we quantified tagasaste production characteristics. Here, we determine the effect of proximity of 10-year-old tagasaste trees on productivity of eight pasture species including grasses (perennial ryegrass, Lolium perenne; cocksfoot, Dactylis glomerata; prairie grass, Bromus willdenowii; microlaena, Microlaena stipoides), perennial legumes (white clover, Trifolium repens; red clover, T. pratense; lotus, Lotus pedunculatus), and an annual legume (subterranean clover, T. subterraneum).

Methods: A site was established in the East Coast region of the North Island of New Zealand on steep-hill country (>20° slope). Herbage production, nutritive value and survival of pasture species established as spaced transplants were measured over 3 years.

Results: Cocksfoot had high survival, herbage production and metabolisable energy content but was negatively affected by proximity to tagasaste. Microlaena was not significantly affected by proximity to tagasaste; however, it was much less productive and had lower nutritive values than the other grasses. Only 40% of perennial ryegrass transplants survived 3 years, and survival of perennial legumes was negligible. Subterranean clover was able to set seed in the open and in shade.

Conclusions: Cocksfoot was the most productive grass species, and microlaena was least affected by proximity to tagasaste. Given the poor persistence of perennial clovers, annual clovers may be better suited to a tagasaste silvopasture on steep, dry hillsides.

Implications: Mixtures of cocksfoot and subterranean clover may be well suited to summer-dry hillsides, between and under trees in a tagasaste silvopasture. Microlaena may provide some forage and can maintain groundcover despite shade.