Search

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. Growth and survival of eight pasture species in proximity to the forage shrub tagasaste were quantified in drought-prone hill country. Cocksfoot and subterranean clover were highly productive only in lightly shaded areas, whereas microlaena, although less productive than other grasses, was not significantly affected by shade treatment, and perennial legumes showed negligible survival. Cocksfoot and subterranean clover could be established between trees in a tagasaste silvopasture, with naturalised microlaena maintained beneath the canopy to provide groundcover. [ABSTRACT FROM AUTHOR]

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]

Perennial ryegrass (Lolium perenne L.) is a widely sown pasture species in temperate regions. Under heat and moisture-deficit stress, its production is suppressed and tiller mortality increases, particularly when plants are simultaneously exposed to other stresses such as intense defoliation. We investigated the effects of extended grazing exclusion periods in spring and summer on herbage and soils of rotationally grazed, perennial ryegrass-dominant pastures at a summer-wet site and a summer-dry site in sheep and beef hill country in New Zealand. Treatments comprised 'grazed' (conventional rotational grazing), 'early opening' (grazing exclusion from mid-spring to mid-summer to allow perennial ryegrass to flower), and 'deferred grazing' (grazing exclusion from mid-spring to late summer to allow perennial ryegrass to flower and set seed). At both sites, deferred grazing increased perennial ryegrass tiller density and total vegetation cover, and reduced the abundance of broadleaf species and Pseudopithomyces chartarum spores for up to 15 months after exclusion compared with the grazed control. Herbage production was reduced during the deferred period but there was a growth surge thereafter so that herbage production over the study period was similar in the deferred and grazed treatments. Pasture nutritive values were lower in the deferred than the grazed treatment during the exclusion period but were similar in all treatments by the end of the following winter. In the autumn after deferring, seedlings contributed ~50% of the perennial ryegrass tillers present at the summer-dry site but only ~10% at the summer-wet site, where regrowth tillering of existing plants contributed a high proportion of the perennial ryegrass tillers present. Overall, early opening had few effects on the pasture, whereas deferred grazing had numerous positive effects on the pasture but only short-term effects on soil quality. We investigated the impacts of deferred grazing (livestock excluded from mid-spring to late summer to enable perennial ryegrass to flower and set seed), early opening (livestock excluded from mid-spring to early summer to enable perennial ryegrass to flower) and standard rotational grazing on hill country pastures and soils under beef and sheep grazing. Compared with standard rotational grazing, deferred grazing had positive effects on pasture productivity but only short-term effects on soil quality, whereas early opening had few effects on the pastures or soils. [ABSTRACT FROM AUTHOR]

For Australian and New Zealand dairy farms, the primary source of home-grown feed comes from grazed perennial pastures. The high utilisation of perennial pasture is a key factor in the low cost of production of Australian and New Zealand dairy systems and, hence, in their ability to maintain international competiveness. The major pasture species used are perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.), normally grown in a simple binary mixture. As pasture production has been further driven by increasing use of nitrogen fertiliser and irrigation, farms are getting closer to their economic optimum level of pasture utilisation. Increasing inputs and intensification have also increased scrutiny on the environmental footprint of dairy production. Increasing the diversity of pasture species within dairy swards presents opportunities to further increase pasture utilisation through additional forage production, extending the growing season, improving forage nutritive characteristics and, ultimately, increasing milk production per cow and/or per hectare. Diverse pastures also present an opportunity to mitigate some of the environmental consequences associated with intensive pasture-based dairy systems. A consistent finding of experiments investigating diverse pastures is that their benefits are due to the attributes of the additional species, rather than increasing the number of species per se. Therefore, the species that are best suited for inclusion into dairy pastures will be situation specific. Furthermore, the presence of additional species will generally require modification to the management of dairy pastures, particularly around nitrogen fertiliser and grazing, to ensure that the additional species remain productive and persistent. Diverse pastures offer benefits to pasture-based dairy systems in terms of increased forage and animal production, improved resilience and the potential to reduce nitrate leaching. The management required to maintain the diversity in the pastures may limit their application. However, the benefits of diverse pastures can be archived with only three species making their management and application simpler. [ABSTRACT FROM AUTHOR]

Abstract: Grazing semi-natural grasslands may enhance their wildlife faunal diversity and abundance by modifying the plant species composition through exploiting the dietary choices of the domestic livestock, yet diet preferences in these grasslands are often poorly understood. We therefore investigated diet selection of beef cattle in semi-natural pastures, grazed at moderate stocking (MS) or lenient stocking (LS), using the global positioning system (GPS) to track their foraging paths. This was combined with use of an automatic system to record foraging behaviour in free-ranging ruminants and measurements of vegetation structure (pasture height and plant functional groups) at a given location. The diet selected by each animal at each grazing location was then determined from a vegetation map surveyed using GPS along with a geographical information system (GIS). Patches containing clover comprised only 17.5% and 3.1% cover in the MS and LS swards, respectively. Clover was also mostly distributed in the sward as singular patches, rather than as larger aggregated clumps and it appeared that these species were not as strongly selected as has been reported for less heterogeneous pastures where they are more prevalent. This study demonstrated that GPS tracking of livestock foraging paths could be combined with vegetation mapping and automatic grazing behaviour measurements to investigate diet preference in complex, heterogeneous swards. [Copyright &y& Elsevier]

1. Vulpia ( Vulpia bromoides and V. myuros) and barley grass Hordeum murinum are prevalent annual grass weeds of native grasslands and grazed pastures in temperate climates, for which more effective control strategies are needed. Annual grass weeds can negatively impact natural grassland ecosystem function, in addition to causing productivity loss in agricultural systems. 2. We investigated the effects of gap size, time of sowing, grazing method (continuous or rotational grazing) and species sown in the gap (vulpia and/or barley grass) on vulpia and barley grass panicle production and intrinsic rate of population growth (λ) in southern Australian pastures. From these data, we estimated the critical gap size below which vulpia and barley grass populations would decline (λ < 1). 3. Panicle production declined rapidly with decreasing gap size, particularly in rotationally grazed pastures. Barley grass produced more panicles than vulpia in some treatments, while time of sowing, and sowing these annual species in mixture had little effect on panicle production. 4. The rate of population growth (λ) increased with gap size, but at the same rate in rotationally and continuously grazed pastures. There was no effect of annual species treatment (vulpia or barley grass) or time of sowing on the rate of population growth. The critical gap diameter was 0·04 cm and 2·31 cm for continuously and rotationally grazed pastures, respectively. 5. A sensitivity analysis showed that reducing plant fecundity (seeds plant−1) and propagule survival prior to seedling establishment by 60% could increase the critical gap diameter by 1·8 cm. 6. Synthesis and applications. The results of this study highlight the importance of minimizing bare ground throughout autumn and winter to suppress annual grass weed population growth, as λ was unaffected by time of sowing. Estimates of λ and the critical gap diameter show that rotational grazing will better control weedy annual grasses than continuous grazing. Further, similar sensitivities of the critical gap diameter to fecundity and propagule survival prior to establishment lend support to weed management strategies that focus on reducing both fecundity and propagule survival. [ABSTRACT FROM AUTHOR]