Effects of treading and defoliation height on the growth of Paspalum dilatatum Poir

Monocultures and mixtures of perennial ryegrass ('Grasslands Nui') and paspalum (,Grasslands Raki') were grown at high (24°C day/18°C night) and low (14°C day/8°C night) temperatures either continuously for 24 weeks or transferred between temperatures at 12 weeks. Defoliation treatments applied were cutting at 2-and 4-weekly intervals and frequent cutting immediately after temperature changeover. The effects of these treatments on dry matter production, tiller number per plant, and light interception are reported. Averaged over both grasses and their mixtures, yields were highest under high temperature and infrequent cutting. There was marked species x temperature interaction. Paspalum yielded most at high temperature and ryegrass at low temperature. Ryegrass-paspalum mixtures outyielded the monocultures and mixtures provided more stable yields over the range of temperature conditions. Response of the grasses to temperature changed with time. Ryegrass initially grew more rapidly at high temperature, but after 12 weeks growth, had higher yields at low temperature. Paspalum growth was severely reduced when transferred from high to low temperature, and rapidly increased when transferred from low to high temperature. Canopy development and consequently light interception was restricted, especially for paspalum, by low temperatures and by frequent cutting. Ryegrass had fewer but larger tillers at high compared to low temperature, and it rapidly changed to the contrasting habit form after temperature transfer. Paspalum tillers were short, prostrate, and largely below cuttmg height at low temperature, but elongated rapidly above cutting height at high temperature. Frequent cutting increased the tiller number of paspalum and reduced the tiller number of ryegrass. Because mutual shading occurred amongst competing plants in a simulated sward situation, these results from controlled environment conditions are more closely applicable to the field situation than results obtained from isolated plants. Use ofryegrass-paspalum mixtures in northern New Zealand and management objectives to obtain efficient light interception and tiller populations are discussed.

Section: Discussionsupporting

confidence: 82%

Temperature and cutting effects on the growth and competitive interaction of ryegrass and paspalum

Harris¹,

Forde²,

Hardacre³

1981

“…This suggests that the extra stress of grazing in summer exposed the introduced rye grass plants to the detrimental effects of paspalum growth. Rhizomatous species (e.g., paspalum) are better at maintaining growth than non-rhizomatous (e.g., ryegrass) species under severe defoliation, heavy treading, and periods of water stress (Weaver 1930;Weinmann 1948;Hunt 1979). The lower summer growth of rye grass in Pa compared to NPa plots (e.g., Fig.…”

Section: Nitrogen Responsesmentioning

confidence: 98%

Renovation of pastures containing paspalum 2. Effects of nitrogen fertiliser on the growth and persistence of overdrilled ryegrass

Thom

Sheath²,

Bryant

et al. 1986

The effects of nitrogen fertiliser on the growth and persistence of ryegrass seedlings transplanted into plots with high or low levels of paspalum were investigated in two field experiments over successive years. Ryegrass seedlings were introduced in July of each year, simulating autumn overdrilling, and were permanently identified. Rates of nitrogen varied from 48 to 67 kg/ha and were applied between August and October. Plots were grazed by cows at intervals. Half the plots were covered by wooden cages during each grazing and were defoliated by clipping. These experiments confirmed the high summer losses of introduced ryegrass plants as previously reported. Large growth responses to nitrogen fertiliser (50 -350070 for herbage dry weight, tiller length, tiller number) by the introduced ryegrass were obtained, but these were insufficient to improve survival. The effects of grazing interval, climatic stresses, competitive resident species, cow damage during grazing, and the presence of paspalum were also considered to influence ryegrass survival.

“…In studying such pastures, Sturme (1977) noted that perennial ryegrass was usually excluded from paspalum clumps. Because paspalum has an exceptional colonising ability (Hamblyn 1937), growth potential during summer (Hatch & Slack 1970), and ability to withstand treading (Hunt 1979) and severe grazing (Weinmann 1948;Harris 1978), this species offers severe competition to establishing plants. Nevertheless, paspalum occupied only 30 -401170 of the experimental area so other resident species must also have offered vigorous competition to establishing species.…”

Section: Discussionmentioning

confidence: 99%

Renovation of pastures containing paspalum 1 . Persistence of overdrilled ryegrass and prairie grass and effect on seasonal pasture production

Thom

Sheath²,

Bryant

et al. 1986

The persistence of Nui ryegrass and Matua prairie grass was measured over a 2-year period, after over drilling into pasture containing paspalum. Ryegrass and a mixture of rye grass and prairie grass were direct drilled in autumn through triple disc or chisel coulter assemblies. Half the width of each main plot received paraquat in 40 mm bands covering the drill lines while the other half did not. The plots were rotationally grazed by dairy cows. Ryegrass and prairie grass seedlings were tagged, and sequential growth measurements (tiller number and length) were made during each plant's life cycle. Losses (30-40%) of plants were highest in the summer following their introduction, and by the end of the study were higher for prairie grass (83070) than for ryegrass (65%). Twenty percent of total losses were ascribed directly to 'animal effects' mainly plant removal ('pulling'), and these were higher for prairie grass than for ryegrass. Coulter type and band-spraying of paraquat had no effect on plant survival. Species mixture had inconsistent effects. Large plants (20-30 tillers) had a higher probability of surviving over summer than did small plants « 10 tillers). The high losse~ of introduced plants was reflected in only small (< 500 kg/ha), short-term (abou16 months after drilling) improvements in pasture production. Practical suggestions are made for improving the survival of over drilled species and these are examined in subsequent papers.