Ryegrass Tiller Density Research Articles

Influence of the ryegrass endophyte (Neotyphodium lolii) in a cool moist environment. I. Pasture production

The ryegrass endophyte, which has been linked to animal disorders and increased pest resistance of its host in a range of environments in New Zealand, was studied in a field experiment in Southland, New Zealand. In contrast with other (warmer and/or drier) environments, the endophyte was found to have minimal effects on pasture production and composition in years with adequate summer rainfall, but endophyte did suppress clover growth (P = 0.028) under summer drought conditions. There was no difference between endophyte‐infected and endophyte‐free treatments for ryegrass tiller densities, number of clover growing points, total herbage production, herbage composition, and the chemical (elemental concentrations and digestibility) composition of ryegrass. The proportion of endophyte‐infected tillers did not change significantly over a five year period, and peak lolitrem B (1.2 ppm) and ergovaline (0.8 ppm) concentrations in the ryegrass component were lower and the peramine (20 ppm) concentration similar to that reported elsewhere in New Zealand. It is concluded that, in the absence of significant endophyte effects on pasture production and composition, the decision to use endophyte‐infected seed has to be based on an endophyte effect on animal production aspects.

A comparison of diploid and tetraploid perennial ryegrass and tetraploid ryegrass/white clover swards under continuous sheep stocking at controlled sward heights. 3. Sward characteristics and animal output, years 4–8

Results for years 4–8 of a long‐term grazing experiment on swards of a diploid perennial ryegrass (Lolium perenne), var. Contender (D swards), a tetraploid ryegrass, var. Condesa (T swards) and Condesa with S184 white clover (Trifolium repens) (TC swards), direct sown in May 1987, are presented. The swards were continuously stocked with sheep from 1988 to 1990, as previously reported, and for a further 5 years, 1991–95, at a target sward surface height (SSH) of 4–6 cm. Control of sward height was successfully achieved by variable stocking, except in 1993 when paddocks were set stocked and the resulting mean SSH was 9·3 cm. Grass swards received on average 160 kg N ha−1 year−1; grass/clover swards were mainly not fertilized with N with the exception that they were given 30 kg N ha−1 as a remedial mid‐summer application during a period of low herbage mass on offer in 1994 and 1995.Mean white clover content of the swards fell from 18·2% of herbage dry‐matter (DM) in 1992 to 8·5% in 1993, whereas stolon lengths fell from 120 to 58 m m−2. A return to lower sward heights in 1994–95 resulted in an increase in white clover content to 12·8% by the final sampling in August 1995. Perennial ryegrass content of the grass swards remained high throughout (mean 96·7% in 1995). Perennial ryegrass tiller densities recorded in August 1991, 1993 and 1994 showed consistently significant (P < 0·001) sward differences (3‐year mean 16 600, 13 700 and 10 100 perennial ryegrass tillers m−2 for the D, T and TC swards). In 1994, the year after lax grazing, a low perennial ryegrass tiller density (9100 m−2) and low white clover content (mean 4·3%) in the TC swards resulted in a much lower herbage bulk density than in the grass swards (April–July means 72, 94 and 44 kg OM ha−1 cm−1 for the D, T and TC swards). There was a consistent 40 g d−1 increase in lamb liveweight gain on the TC swards over the T swards, except in 1994. In that year there was a reduction in lamb liveweight gain of 33 g d−1 on the TC swards and a significant increase in ewe liveweight loss (117 g d−1) associated with low herbage bulk density despite optimal sward height. Lamb output (kg liveweight ha−1) on TC swards reflected white clover content, falling from a similar output to that produced from grass given 160 kg N ha−1, at 18% white clover DM content, down to 60% of grass + N swards with around 5% clover. A 6% greater output from the T than the D swards was achieved mainly through higher stocking rate. The experiment demonstrated a rapid, loss in white clover under lax grazing, and showed that the relationship between performance and sward height is also dependent on herbage density. High lamb output from a grass/clover sward was only achieved when the clover content was maintained at 15–20% of the herbage DM.

Effect of defoliation frequency on an irrigated perennial pasture in northern Victoria. 1. Seasonal production and sward composition

A field experiment was carried out to investigate whether changes in winter and post-winter defoliation frequency would increase the white clover content of an irrigated perennial ryegrass–white clover pasture in northern Victoria. Pastures defoliated every 4 weeks during winter had higher white clover growing point (stolon apices with at least 2 nodes) density at the end of winter than pastures defoliated every 8 weeks or those receiving a single defoliation after 16 weeks, but these differences did not affect the clover content in the spring. Reasons for this are suggested. Pastures defoliated at 8-week intervals in winter were the most productive over winter{early spring. Less frequent defoliation (4 v. 2 weeks) during the post-winter, September–May period reduced white clover growing point and perennial ryegrass tiller densities. However, the white clover growth rate during this period was increased by less frequent defoliation, whereas the ryegrass growth rate was reduced, resulting in an increase of 10% in the white clover content, and a 1·9 t dry matter (DM)/ha increase in total DM produced. This higher clover content and pasture yield during spring–autumn with less frequent defoliation has important implications for the management of irrigated perennial pastures for the dairy industry in northern Victoria.

Effect of high rates of nitrogen fertiliser on perennial ryegrass growth and morphology in grazed dairy pasture in northern New Zealand

Abstract Nitrogen (N) fertiliser was applied to dairy pastures at rates of 0,200, or 400 kg N/ha per year on farmlets stocked at 3.24 (LS) or 4.53 (HS) Friesian cows/ha from June 1993 to June 1995. Annual net herbage accumulation increased 22 and 23% on farmlets LS200 and HS200 respectively, and 37 and 24% on farmlets LS400 and HS400. Most of the extra herbage was perennial ryegrass. Ryegrass contents (% total dry matter (DM)) were 71 and 76% on farmlets LS200 and LS400 respectively compared with 61% on farmlet LS0. Ryegrass tiller densities were also higher on farmlets LS200 and LS400 (6295 and 6673 tillers/ m2 respectively) than on farmlet LS0 (4072 tillers/ m2). On all farmlets there was a post‐flowering (January‐February) increase in tiller density although this increase was enhanced by N. N application also increased tiller number/plant (3.37, 4.10, and 4.26 tillers/plant on farmlets LS0, LS200, and LS400 respectively). The greater leaf number and leaf dry weight (DW)/plant on farmlets LS200 and LS400 was connected to the increased tiller number/plant, although DW/leaf was also significantly (P < 0.05) greater under N. There was no N effect on leaf sheath or basal stem, but DW/ tiller was significantly (P < 0.05) greater. Ryegrass plants formed two types of internodal stolon: I(v) associated with vegetative growth throughout the year; and I(r) associated with reproductive growth and only formed during November—January. N had no effect on I(v) formation but 35 and 34% of plants formed I(r) on farmlets LS200 and LS400 respectively compared with 22% on farmlet LS0. It is suggested the positive effects of N on tiller number and DW/plant together with the post‐flowering increase in tillering may improve persistence of perennial ryegrass in intensively grazed dairy pastures.

The Influence of Elevated CO 2 and Simulated Seasonal Changes in Temperature on Tissue Turnover in Pasture Turves Dominated by Perennial Ryegrass (Lolium perenne) and White Clover (Trifolium repens)

1. Tissue turnover, leaf morphology and population dynamics of perennial ryegrass and white clover were studied in pasture turves grown at ambient (350 μmol mol −1 ) or double ambient (700 μmol mol −1 ) CO 2 concentrations for 217 days in controlled environment rooms. The turves were subjected sequentially to three day/night temperature regimes; 10/4°C, 16/10°C and 22/16°C and harvested at 3-week intervals. The photoperiod was 12 hours for all of the temperature treatments with a mean photon flux density of 480 μE m −2 s −1 . 2. Ryegrass leaf extension and leaf death rates did not differ between CO 2 treatments and there was no effect of CO 2 on rates of leaf appearance in white clover. Weight per unit length of ryegrass laminae was unaffected by elevated CO 2 but lamina weight per unit area, lamina area and petiole weight per unit length in white clover showed a small positive response, especially at the two higher temperatures. Rates of growth and senescence per ryegrass tiller were therefore similar between CO 2 treatments, but rates of growth per white clover growing point were increased by 4, 23 and 13% at 10/4°C, 16/10°C and 22/16°C, respectively, at elevated CO 2 . Responses to CO 2 could not be attributed to any consistent change in morphological characteristics in either species and exposure to elevated concentrations of CO 2 did not appear to change the relationship between growth and senescence per meristem. 3. Total grass tiller populations were similar at both CO 2 concentrations, but ryegrass tiller densities more than halved in both CO 2 treatments as the temperature was increased. The fall was most severe at 700 μmol mol −1 and at the end of the experiment ryegrass tiller densities in this treatment were only 47% of those found at 350 μmol mol −1 . There was no consistent effect of CO 2 concentration on clover growing point numbers and they increased from 800 m −2 to over 3000 m −2 in both treatments with maximum densities occurring at 22/16°C. 4. The results imply that, in plant communities dominated by ryegrass and white clover, exposure to elevated CO 2 concentrations will alter the species composition in favour of white clover. Responses in above-ground dry matter yield to elevated CO 2 will be a balance between the positive response shown by white clover and the negative response of perennial ryegrass. Temperature will have a major influence on the magnitude of this response since both the response of white clover to CO 2 and the ratio of white clover growing points to ryegrass tillers are temperature-dependent

A comparison of diploid and tetraploid perennial ryegrass and tetraploid ryegrass/white clover swards under continuous sheep stocking at controlled sward heights. 1. Sward characteristics

AbstractTwo 1·0 ha plots of a late‐heading diploid perennial ryegrass (var. Contender) and a late‐heading tetraploid ryegrass (var. Condesa), and two 1·4 ha plots of the tetraploid with Aberystwyth S184 small‐leaved white clover, were direct sown in May 1987. Over the three years 1988–90 they were continuously stocked by Mule ewes with Suffolk‐cross twin lambs, from early April to the end of August, at a target sward surface height (SSH) of 4–6 cm on one set of plots (constant swards) and, on the other set, al 4–6 cm rising after June to a target 6–8 cm (rising swards). The heights were achieved by variable stocking. Fertilizer N was applied only to the grass plots at the rate of 150‐ 180kgN ha‐1 annually.SSH was mainly within the target 4–6 cm, after higher initial heights at turnout in 1988and 1990. Mean heights of the constant swards (April‐ August) averaged 5·53, 4·43 and 5·04cm in the three years. The rising swards (July‐August) increased in height over the constant swards by an average of 0·88, 0·48 and 0·55 cm, in successive years.Clover content of the herbage mass dry matter in the grass/clover swards increased over each grazing season to average 13·0, 26·5 and 21·2% in the three years, with a high mean stolon density of 130 in m‐2 in August 1990. Ryegrass tiller densities in year 3 were 23% higher in the diploid than in the tetraploid swards, which had 43% more than the 10000 tillers m‐2 of the tetraploid ryegrass/clover swards.It is concluded that the combination of a densely stoloniferous small‐leaved clover with the open growth habit of a tetraploid ryegrass can achieve swards of high clover content under continuous sheep stocking.

Spring grazing management and tiller dynamics in a ryegrass/white clover pasture

The objective of this trial was to study the effect of variation in the timing and duration of lax spring grazing on tiller dynamics in perennial ryegrass. Tiller population density, tiller appearance, and tiller death were measured in a sward of perennial ryegrass (cv. Grasslands Nui) and white clover (cv. Grasslands Tahora) grazed by sheep every 14 days to 4 cm (hard) and every 21 days to 7 cm (lax) residues. The experiment comprised 2 lax spring grazing treatments [lax grazing October 26December 8 (H-H-L-H) and September 16 December 8 (H-L-L-H)], plus a hard grazed control (H-H-H-H). Ryegrass tiller density was greater in H-L-L-H than H-H-L-H and H-H-H-H from mid summer until the end of the trial in autumn, mainly because of the difference in tillering activity late in December. Tiller appearance rate increased in all the treatments from September to the end of January, and was particularly high late in December in the second regrowth after grazing of the apices of the main group of reproductive tillers. The lax grazing management strategy increased tiller appearance rate during late December and January. Higher tiller losses in lax grazing treatments over the same period were not offset enough to affect this advantage. The response in tiller population density was greater following the extended period of lax spring grazing. Keywords: grazing management,Lolium perenne, reproductive growth, tiller population density, tiller demography, Trifolium repens

Influence ofAcremonium loliiinfection in perennial ryegrass on germination, emergence, survival, and growth of white clover

Abstract Four glasshouse experiments and two field trials were conducted to determine the effects of perennial ryegrass (Lolium perenne L.) infected with Acremonium lolii Latch, Christensen & Samuels on white clover (Trifolium repens L.) germination, emergence, growth, and survival. Under controlled laboratory experiments, ryegrass leachates temporarily inhibited the rate of white clover germination, but did not affect white clover emergence or yield. In glasshouse experiments, the presence of A. lolii did not influence white clover emergence or growth. Emergence of indicator plant species grown in pumice sand substrate which previously grew ‘Ellett’ or ‘Grasslands Nui’ perennial ryegrass was not affected (‘Ellett’) or was enhanced (‘Grasslands Nui’) by the presence of A. lolii. In field trials, A. lolii infection did not significantly affect white clover survival, vigour, or leaves and stolons per plant, when ryegrass tiller densities were similar. Later, when tiller density of A. lolii-free plants decre...

Stolon development in grazed ‘Grasslands Nui’ perennial ryegrass

Abstract Turf was taken from grazed ‘Grasslands Nui’ perennial ryegrass (Lolium perenne L.) + ‘Grasslands Huia’ white clover (Trifolium repens L.) pastures to count ryegrass stolons and locate tillers on stolon nodes. In the first experiment, eight grazing treatments were sampled in summer. Ryegrass tiller density was 6985 tillers/m2, stolon density 2420 stolons/m2, and 79% of ryegrass tillers were attached to stolons. Grazing treatments did not significantly influence the density of stolons, but more intensive grazing during late spring and early summer reduced the number of internodes on stolons. In a second experiment, turf was taken during spring and summer to study the timing of stolon formation. Stolon density was low in early spring (40 stolons/m2, increased during culm elongation (450 stolons/m2 at inflorescence emergence), then increased markedly after grazing killed reproductive tillers (2000 stolons/m2 in summer). Stolons developed when basal internodes of vegetative tillers elongated and roots...

Tiller appearance and death ofLolium perennein mixed swards grazed by dairy cattle at two stocking rates

Abstract Ryegrass tiller appearance, death, and density were examined in perennial ryegrass — white clover pastures stocked with 2.77 (LSR) or 4.28 (HSR) dairy cows per hectare. Rates of tiller appearance and death were highest between November and January and were low and variable between February and October. Tillering in autumn was low and similar to that in winter (27.8 and 27.7 tillers/m2 per day, respectively). The rate of tiller death (but not appearance) was influenced by stocking rate, and was greater (P<0.01) in LSR than HSR swards during spring (29.5 and 21.2 tillers/m2 per day, respectively) and summer (61.3 and 39.9 tillers/m2 per day, respectively). Higher tiller death rates in LSR swards resulted in lower (P<0.05) tiller density during summer and autumn and reduced heterogeneity of tiller age population. Herbage mass in autumn was composed of more (P<0.05) new tillers in LSR than HSR swards (61.1 and 46.4%, respectively). Herbage mass in winter and spring consisted of a variety of tiller ag...

Effects of the timing and intensity of spring grazings on reproductive development, tillering, and herbage production of perennial ryegrass dominant pasture

Abstract Reproductive development, tillering, and herbage production were studied in mixed pastures containing ‘Grasslands Nui’ perennial ryegrass (Lolium perenne L.) and ‘Grasslands Huia’ white clover (Trifolium repens L.), which were rotationally grazed by sheep. The effects of interruption of ryegrass reproductive development during early culm elongation (TI) or 30% inflorescence emergence (T2), by either hard grazings (H; residual leaf area index (LAI) 0–0.7) or lax grazings (L; residual LAI 0.8–2.2) were compared. These grazing intensity treatments were continued until mid summer; and in late summer and autumn all pastures received the same grazing management. Culm elongation in an initial group of reproductive tillers, 2400/m2, started in October, and 30% inflorescence emergence occurred in mid November. During November and December a further 1000/m2 secondary reproductive tillers appeared. Few new reproductive tillers appeared after December. Vegetative ryegrass tiller density declined markedly dur...

The comparative effects of defoliation, treading and excreta on a Lolium perenne-Trifolium repens pasture grazed by sheep

SUMMARYThe effects of treading and the return of excreta on a Lolium perenne-Trifolium repens sward defoliated by sheep set-stccked at high and low stocking rates were examined. Sward performance was measured inside ‘graze-through’ cages which allowed defoliation without treading and excreta return, and outside where sheep grazed either fitted with harness to prevent the return of excreta or unharnessed to allow the normal return of excreta. Live-weight gain was measured from excreta return and non-return swards. The treatments imposed had large effects on herbage growth and botanical composition.At a stocking rate of 25 yearling wethers/ha, sheep excreted about 1·1 kg N/ha/day, which increased soil N and led to an increase in herbage growth of about 26 %. The return of excreta increased ryegrass tiller density and this was partly responsible for a 26% reduction in the proportion of clover in the sward; the weight of clover was 13% loss where excreta were returned, and on this treatment stolon length at the end of the experiment was similar to that at the beginning. Doubling the stocking rate increased the N returned via excreta to about 1·3 kg N/ha/day, and this increased herbage growth by 53% but suppressed the proportion of clover by 21%, though not the weight of clover. Clover stolon length decreased during the experiment at this stocking rate, both with and without the return of excreta. Sheep live-weight change benefited from the stimulus to herbage growth where excreta were returned at the high stocking rate, but not at the low stocking rate.Treading by 25 sheep/ha increased soil compaction but had no significant (P &gt; 0·05) overall effect on herbage growth and botanical composition. However, treading by double the number of grazing animals significantly reduced herbage growth by 10%, plant root weight by 47% and the proportion of clover in the sward by 11%.Differences in sward performance between stocking rates were due more to the difference in defoliation intensity between these stocking rates than to either treading or the return of excreta.

Use of residual leaf area index and light interception as criteria for spring-grazing management of a ryegrass-dominant pasture

Abstract Detailed measurements of herbage accumulation were made on a ‘Grasslands Nui’ perennial ryegrass (Lolium perenne)-dominant, ‘Grasslands Huia’ white clover (Trifolium repens) pasture under 4 late spring grazing intensities, based on residual leaf area index (LAI), and 2 grazing frequencies based on light interception. Lax grazing during late spring (residual LAI 0.9–3.0) resulted in rank stalky herbage, whereas hard grazing (residual LAI 0.1–0.9) resulted in more leafy herbage and higher ryegrass tiller density. For the 46 weeks of the experiment, 16.5 and 14.61 DM/ha accumulated with hard and lax spring grazing respectively. During autumn, delaying grazing until 2 weeks after 95% light interception markedly increased green herbage accumulation compared with grazing at 95% light interception, without significantly reducing ryegrass tiller density or white clover content. It is concluded that in spring, in contrast to other seasons, management of ryegrass-dominant pasture to control reproductive de...

Selective herbicides for establishing weed‐free grass. I. Evaluation of ethofumesate and methabenzthiazuron

Summary:The consequences of using two pre‐emergence herbicides on autumn‐sown perennial ryegrass (Lolium perenne L.) were measured over 3 years in a field experiment. Ethofumesate (2‐ethoxy‐2,3‐dihydro‐3,3‐dimethylbenzofuran‐5‐yl melhylsul‐phonate) and methabenzthiazuron [N‐(benzothiazol‐2‐yl)‐N, N'‐dimethylurea] were each applied at 0, 0.8, 1.6 and 3.2 kg ha−1 one week after drilling the grass seed. Monthly counts of plants per unit area and tillers per plant were made until the following April and the herbage dry weights of the major species were recorded at seven harvests.Heavy infestations of Stellaria media (L.) Vill. and Poa annua L. occurred on untreated plots. Ethofumesate, and to a lesser extent methabenzthiazuron, proved effective in suppressing these weeds, only low rates being needed to control S. media. Both weeds needed to be controlled to achieve full benefits to the crop; control resulted in a 4‐fold increase in ryegrass tiller density by the first spring and a 6‐fold increase in ryegrass herbage was recorded at the first harvest in May. Some yield benefits were carried over into the second year but not into the third. In total, an extra 4.16 t ha−1 of ryegrass dry‐matter was harvested from plots treated with ethofurnesate at 0.8 kg ha−1 compared with the controls. The results are discussed in terms of defining optimum crop densities when pre‐emergence herbicides are used.