Pasture establishment

Two months after sowing, there was an indication (P=0.067) of a higher mean number of seedlings for all species at Ladbrooks compared with Ashley Dene. The number of seedlings/metre of drill row for perennial ryegrass was higher than brome and cocksfoot at Ladbrooks. At Ashley Dene, the number of seedlings for perennial ryegrass was ~1.5 times higher than other species. However, this was not significantly different (P=0.53) due to a high CV at Ashley Dene compared with Ladbrooks. The mean number of seedlings for tall fescue (63.4) was intermediate at both sites.

There was no interaction (P=0.64) among species in root weight between the sites. However, the mean root weight was lower (P<0.05) for cocksfoot than other species at both sites (Figure 4-5). The lowest seedling root biomass of cocksfoot at both sites is probably due to its slower germination/emergence (Chapter 3) and establishment (Charlton and Stewart, 1999) compared with the other grass species in the current study. Previous studies also showed that, cocksfoot germination/ emergence (McWilliam

et al., 1970) and also establishment (Charlton and Stewart, 1999) were slower than brome, tall fescue

and especially perennial ryegrass.

The lower PAWC at Ashley Dene compared with Ladbrooks caused 43.7%, 63.1% and 72.4% lower shoot biomass for brome, tall fescue and perennial ryegrass, compared with 28.9% for cocksfoot. These results demonstrate that cocksfoot was slower to establish. However, with the lower moisture content available in the Lismore stony soil at Ashley Dene, compared with the Wakanui silt loam soil at Ladbrooks, the cocksfoot seedlings root and shoot biomass were affected less than the other species.

108

After 62 DAS at Ladbrooks, shoot dry weight of perennial ryegrass, tall fescue and cocksfoot was 0.127, 0.101 and 0.0521 g which were similar to a previous study which showed 0.176, 0.91 and 0.34 g seedling weight respectively for the same species at 57 DAS (Moot et al., 2000). At the same time at Ashley Dene, shoot dry weight of perennial ryegrass and tall fescue was ~0.045 g which was four and two times less than the results from Ladbrooks and also the results showed by Moot et al. (2000). This also confirms the effect of drought on shoot weight of perennial ryegrass and tall fescue which influenced shoot weight of ryegrass seedlings more than tall fescue under the same level of moisture stress at Ashley Dene.

At both sites, seedling shoot dry weight was higher (P<0.01) for brome and perennial ryegrass. Compared with other species, the larger seeds for brome contain more seed reserve and appear to have enabled its seedlings to grow faster than other species. Shoot dry weight for perennial ryegrass seedlings was higher than tall fescue and cocksfoot which is reportedly be due to its use of endosperm reserve for faster germination/emergence (Brock et al., 1982). Earlier emergence also allowed plants the ability to expand the leaves, intercept light and utilise moisture and nutrients earlier faster than slower emerging species. The rapid emergence of perennial ryegrass (Section 2.8.6) is one of the reasons it is favoured as a pasture species even though it may not persist dryland environments. The root/shoot ratio was not different among species but was higher at Ashley Dene, due to the high shoot dry weight (P<0.01) at Ladbrooks. This suggests, the higher PAWC at Ladbrooks did not affect root biomass but enabled higher shoot DM compared with Ashley Dene which was due to higher leaf expansion and radiation interception by the seedlings leaves at Ladbrooks. Reduced leaf area is the most obvious response of plants to restricted water availability (Section 2.3.1), and this caused seedlings to have less shoot weight at Ashley Dene with a lower PAWC compared with the seedlings at Ladbrooks.

Easton (1994) reported that the slower establishment of tall fescue particularly compared with ryegrass, is a limitation for its use, and affects its production in the establishment year. However, this was not the case in the current study. The hydrothermal time results (Chapter 3) showed that, ≥60% of ‘Finesse Q‘ tall fescue seeds were able to germinate in a wide range of temperature and water limitation (Section 3.5.5). Also the field experiment results at Ashley Dene showed that, 62 days after sowing, 42% of the tall fescue sown seeds had emerged (Section 4.11.1). This was similar to the number of emerged perennial ryegrass seedlings and was higher than the number of cocksfoot and brome seedlings at the same time. From sowing date to 4/5/2015, before the second application of herbicide at Ashley Dene, tall fescue showed the highest proportion (23%) of the weeds (of mostly browntop and fathen reported in Section 4.11.6) compared with other grasses. This was comparable with 17% for cocksfoot. However, tall fescue production was more vulnerable to invasion by weeds than other

109

grasses at Ashley Dene. Previous studies also reported that tall fescue is more affected to invasion by weeds such as browntop if fertility requirements are limited, like the situation at Ashley Dene in this study (Lambert et al., 2004, Saul and Chapman, 2002).

The number of tillers per plant was not measured in the current study. However, field observations showed that tall fescue had relatively fewer tillers per plant, once established. This is consistent with previous studies that showed, new tiller formation in tall fescue is one-third slower than ryegrass (Milne et al., 1997).