Grazing strategies for resilience of ryegrass (

Abstract

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.

Agronomic performance of summer forage crops on a Waikato dry-stock farm

“…Using the analyses provided by Tozer et al (2021), it has been estimated that deferred grazing could provide approximately 57700 MJ ME/ha, which was similar to that provided by the 21-spp-adj mix in this study, but much lower than that provided by the rape monoculture and simple mixtures containing rape. Assumptions were that (i) there were no costs associated with energy production of deferred pasture; (ii) 2400 kg DM/ ha were produced between 21 September (when the field site was sprayed out) and 31 October with a ME value of 10.7 MJ/ha and growth rate of 60 kg DM/ha/ day, which was typical for mid-spring growth for this farm, and (iii) pasture deferred from 13 October until 26 January (when crops in this study were harvested) accumulated 4000 kg DM/ha with a ME value of 8.0 MJ ME/ha.…”

“…Deferred grazing is a tool that can be used to accumulate pasture for livestock in mid-summer. It has negligible production costs, but the energy yield is likely to be low due to the low nutritive value of the deferred pasture (Tozer et al, 2021).…”

“…Assumptions were that (i) there were no costs associated with energy production of deferred pasture; (ii) 2400 kg DM/ ha were produced between 21 September (when the field site was sprayed out) and 31 October with a ME value of 10.7 MJ/ha and growth rate of 60 kg DM/ha/ day, which was typical for mid-spring growth for this farm, and (iii) pasture deferred from 13 October until 26 January (when crops in this study were harvested) accumulated 4000 kg DM/ha with a ME value of 8.0 MJ ME/ha. These assumptions were based on interpolated data from Tozer et al (2021) from a replicated field study in Lower Kaimai. The Kaimai site had a similar longitude, pasture-base and rainfall to the farm in the current study.…”

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

“…Perennial ryegrass, cocksfoot and prairie grass can also benefit from grazing exclusion during their reproductive period in late spring-summer. This enables reseeding and stimulates regrowth tillering when conditions are suitable for growth in autumn (Hume et al 1990;Dowling et al 1996;Tozer et al 2021). In our study, all species were defoliated at the same time.…”