Summary. Irrigated, pure stands of perennial ryegrass (Lolium perenne cv. Yatsyn), prairie grass (Bromus willdenodii cv. Matua) and tall fescue (Festuca arundinacea cv. AU Triumph) were compared with Italian ryegrass (L. multiflorum cv. Concord) under grazing in the subtropics of south-east Queensland. Pastures were fertilised with 50 kg nitrogen/ha . month as urea and annual dressings of 20 kg phosphorus/ha and 50 kg potassium/ha (as superphosphate and muriate of potash, respectively). There were 4 pasture treatments grazed by multiparous Holstein-Friesian cows at 3 cows/ha in a 1-week-on, 3-weeks-off rotation with 2 replicates and 3 cows/treatment block. Feed on offer was measured weekly and pasture quality, at the mid point of each of the 4 seasons. Detailed measurements on plant and tiller dynamics were recorded on fixed quadrats within the grazing areas from November to May in the second and third years. Yield of pasture on offer was greatest with prairie grass and the difference was most marked in spring and early summer. Yield of fescue was generally higher than that from the other 3 grasses in the autumn. In the second and third summers, the grass weed component in the 2 ryegrass, and to a lesser extent the prairie grass, pastures was greater than the sown grass component. Fescue generally produced forage lower in quality than the other 3 grasses although the differences were small in summer. The forage quality of Italian ryegrass was higher than perennial ryegrass in most seasons and for most attributes measured. Generally prairie grass had similar quality forage to the ryegrasses but at times it was as low as fescue. Fescue was the most persistent grass; it maintained a frequency of occurrence of 88, 56 and 71% in the first, second and third autumn periods, respectively, compared with 36, 37 and 21% for perennial ryegrass. To achieve these persistence figures, perennial ryegrass needed over-sowing in each autumn. Plant density and tiller numbers per plant fell in all grasses from November to May but the fall was significantly less in fescue than in other grasses. It was concluded that all 3 temperate perennial grasses demonstrated traits which were useful for subtropical dairy pastures. Fescue was the most persistent and the only grass which could sustain grazing in autumn. The performance of Italian ryegrass was as good as that of perennial ryegrass in the first year but fell substantially in the second and third years as the level of summer grass invasion suppressed the existing population and made oversowing increasingly less effective. Prairie grass produced the highest dry matter on offer under grazing, its forage quality was generally similar to that of the ryegrasses and it regenerated from self-sown seed.
Abstract. The dry matter (DM) yield, plant persistence and forage quality of tall fescue (Festuca arundinacea) and perennial ryegrass (Lolium perenne) were compared in the subtropical environment of southern Queensland, Australia. The field study was conducted under irrigation with pure, nitrogen fertilised stands of 10 commercial tall fescue cultivars (Advance, AU Triumph, Bombina, Cajun, Dovey, Maximise, Midwin, Torpedo, Quantum and Vulcan), 3 experimental cultivars (ITF 97010, ITF 97020 and PWF 29) and Dobson perennial ryegrass. From July 1997, plots were defoliated at 4-week intervals for 3 years. Changes in crude protein content and in vitro DM digestibility (IVDMD) were determined at 1, 2, 3, 4, 6 and 8 weeks post-defoliation in October (spring) 1997, January (summer), March (autumn), June (winter) and September (spring) 1998.Some cultivars of irrigated tall fescue were shown to be better adapted to a subtropical environment than perennial ryegrass. After 3 years, cumulative DM yields were in excess of 30 t/ha for Dovey, Quantum, ITF 97010, AU Triumph and Cajun tall fescue compared with 12 t/ha from Dobson perennial ryegrass swards.Plant development had a considerable influence on crude protein content and IVDMD of tall fescue and perennial ryegrass, more so than the length of the regrowth period. As plant tissue matured, the forage quality during spring declined linearly for crude protein content and for IVDMD (1998 only), and declined exponentially for IVDMD during spring (1997), summer, autumn and winter (1998). Quality losses may be minimised if tall fescue cultivars are defoliated every 2-3 weeks during spring and summer and every 3-4 weeks during autumn and winter.
The growth, persistence, and rust sensitivity of a range of temperate grasses were measured to assess their potential for irrigated pastures in the subtropics. Characteristics considered important for adaptation to the subtropics include a relatively even growth rate throughout the year, rust tolerance, and the ability to persist under humid conditions. Cultivars and experimental lines from Lolium perenne (perennial ryegrass), L. rnultiflorum (Italian ryegrass), Festuca arundiizacea (fescue), Festuca x Lolium (festulolium), Bromus spp. (prairie grass and bromes), Dactylis glomerata (cocksfoot), and Phalaris aquatica (phalaris) were sown at Gatton, south-eastern Queensland, in pure stands or mixtures of annual and perennial grasses, using high seeding rates, 50 kg N/ha.defoliation, and full irrigation throughout the year. As a group, the fescues were the highest yielding and most persistent over 2 years, with AU Triumph the highest yielding cultivar. Maru phalaris was the most persistent grass, increasing from a frequency of 85% at the end of the first year to 100% at the end of the second year. Perennial ryegrass yields were about two-thirds those of the fescues, with a frequency of around 70% after 2 years. Dobson was the best ryegrass, producing a greater proportion of its forage in summer and increasing its density over the 2 years compared with the other perennial ryegrasses. Mixtures of annual ryegrass and fescue cultivars produced yields equivalent to pure fescue swards, with production dominated by annual ryegrass in the first year and by fescue in the second. Matua prairie grass was high yielding, but under frequent cutting was not as persistent as the ryegrasses. Felopa festulolium was inferior to the perennial ryegrasses and fescues in yield, the distribution of that yield, and persistence. Weeds contributed 1-10% of total yield over 2 years. The experiment suggests that the fescue cultivars are the most productive temperate grasses for perennial irrigated pastures in the subtropics, although better animal performance would improve farmer acceptance. The addition of a ryegrass component to fescue swards increased yields during establishment but did not improve overall yields. Late-maturing cultivars are the highest yielding of the perennial ryegrasses. Rust sensitivity needs improvement as all the present lines are highly susceptible.
The effects of five levels of nitrogen (N) fertiliser on pasture yield and composition and soil chemical characteristics of Rhodes grass (Cholris gayana) cv. Pasture under grazing and cutting in a subtropical environment of 800 mm annual rainfall were studied over 6 years. Pasture received annual basal dressings of superphosphate (250 kg/ha) and potassium chloride (125 kg/ha for plots, 125 kg/ha . alternate year for grazed paddocks). Urea was applied in 3 equal dressings in September, December, and February, at rates equal to 0, 150, 300, 450, and 600 kg N/ha. year. Stocking rate was 2 Holstein-Friesian milking cows/ha throughout the year, and separate areas of grazing oats (0.4 ha/cow), cracked grain (0.8 t/cow.year), and hay or silage were used to supplement pasture. Under both cutting and grazing, pasture dry matter (DM) yield increased linearly with applied N to about 300 kg N/ha. year, with little further increase at higher levels. Under grazing there was evidence of a decrease in yield at 600 kg N/ha.year, due to total death of the pasture following frosting in winter and the need for regeneration from seedlings in spring; this regeneration was slowed by the large amount of surface litter. Grass N contents decreased and phosphorus and potassium contents decreased with increasing levels of applied N. All 3 nutrients increased from year 1 to 6. Leaf content of grazed pasture was highest during spring (>30% DM) and declined through to autumn (<20% DM), with no consistent effect of N level. Leaf content was consistently higher under cutting (>50%) but was not altered by level of applied N. Soil nitrate-N levels increased (P<0.05) with level of applied N, from 4 to 42 mg/L at 0 and 600 kg N/ha. year, respectively. After 6 years of fertilisation at 300 and 450 N/ha.year, nitrate-N levels were similar to those for 600 kg N/ha.year. Soil pH decreased (P<0.05) with applied N, by 0.15 and 0.28 units annually for 150 and 600 kg N/ha.year, respectively. We conclude that in this environment large responses in pasture growth occur under both cutting and grazing to levels of applied N to about 300 kg N/ha.year, with little response beyond this level.
The effect of fungal endophyte (Neotyphodium lolii) infection on the performance of perennial ryegrass (Lolium perenne) growing under irrigation in a subtropical environment was investigated. Seed of 4 cultivars, infected with standard (common toxic or wild-type) endophyte or the novel endophyte AR1, or free of endophyte (Nil), was sown in pure swards, which were fertilised with 50 kg N/ha.month. Seasonal and total yield, persistence, and rust susceptibility were assessed over 3 years, along with details of the presence of endophyte and alkaloids in plant shoots. Endophyte occurrence in tillers in both the standard and AR1 treatments was above 95% for Bronsyn and Impact throughout and rose to that level in Samson by the end of the second year. Meridian AR1 only reached 93% while, in the standard treatment, the endophyte had mostly died before sowing. Nil endophyte treatments carried an average of ~0.6% infection throughout. Infection of the standard endophyte was associated with increased dry matter (DM) yields in all 3 years compared with no endophyte. AR1 also significantly increased yields in the second and third years. Over the full 3 years, standard and AR1 increased yields by 18% and 11%, respectively. Infection with both endophytes was associated with increased yields in all 4 seasons, the effects increasing in intensity over time. There was 27% better persistence in standard infected plants compared with Nil at the end of the first year, increasing to 198% by the end of the experiment, while for AR1 the improvements were 20 and 134%, respectively. The effect of endophyte on crown rust (Puccinia coronata) infection was inconsistent, with endophyte increasing rust damage on one occasion and reducing it on another. Cultivar differences in rust infection were greater than endophyte effects. Plants infected with the AR1 endophyte had no detectable ergovaline or lolitrem B in leaf, pseudostem, or dead tissue. In standard infected plants, ergovaline and lolitrem B were highest in pseudostem and considerably lower in leaf. Dead tissue had very low or no detectable ergovaline but high lolitrem B concentrations. Peramine concentration was high and at similar levels in leaf and pseudostem, but not detectable in dead material. Concentration was similar in both AR1 and standard infected plants. Endophyte presence appeared to have a similar effect in the subtropics as has been demonstrated in temperate areas, in terms of improving yields and persistence and increasing tolerance of plants to stress factors.
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