Ryegrass Tiller Research Articles

Volunteer winter wheat: its effects and control in ryegrass seed production

SummaryThe effects of different populations of volunteer winter wheal and their control with ethofumesate and TCA on growth, seed yield and yield components of S.24 perennial ryegrass were investigated in lield experiments in 1978 and 1979.Reductions in ryegrass seed yield due to the presence of wheat depended on the density of wheat and the number and dry weight of ryegrass tillers. The greatest percentage reduction in ryegrass seed yield occurred at high densities of wheat (300 plants m−2) when the number of ear‐bearing tillers and 1000 seed weight of ryegrass were reduced. When Ihe density of wheat was low (80 plants m−2) a smaller reduction in ryegrass seed yield occurred and the number of live wheat plants remaining gradually decreased. Within the range of wheat densities in these experiments (0–300 plants m −2) a 1% loss in ryegrass seed yield occurred for every 10 wheal plants m−2 present in the crop post winter.Both herbicides caused a reduction in number of ryegrass tillers during growth but, except where TCA was applied at 12 kg ha−1 in November, ryegrass seed yields were not significantly reduced (in comparison with a wheat‐free control) and were always greater than those obtained in the presence of wheat where no herbicides had been applied. Levels of volunteer infestation of 300 wheat plants m−2 were controlled with minimum risk of crop damage by applications of 6 kg ha−1 TCA in either October or November, or by application of 1–9 kg ha−1 ethofumesate in November.

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 > 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.

Argentine stem weevil effects on Nui and Ruanui ryegrasses grown with two levels of nitrogen/water nutrition

Abstract Monoculture plots of ‘Grasslands Ruanui’ and ‘Grasslands Nui’ perennial ryegrasses were established with high and low nitrogen/water treatments. Twice-weekly examinations of tagged rye grass tillers showed Ruanui with high N/water (RH) to be more severely damaged by Argentine stem weevil larvae than Ruanui with low N/water (RL) or Nui with either treatment (NL and NH). More stem weevil larvae were found in Ruanui plots, and in plots with high N/water. Peak larval densities in RH plots were 1500 larvae/m2 or one per 4.8 tillers. Although RH plots sustained higher rates of stem weevil damage, no similar cultivar × nutrition interaction was detected for larval density. Net growth rates for RH plots were reduced because of high rates of herbage and tiller death during January and February when stem weevil damage was greatest. High rates of tillering in RH plots during April were associated with a recovery of both tiller density and growth rate. It is suggested that studies concerning stem weevil susceptibility should allow for nutritional effects.

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...

The influence of length of growing period, nitrogen fertilization and shading on tillering of perennial ryegrass (Lolium perenne L.).

The formation and death of tillers was studied in swards of perennial ryegrass. These swards differed in the length of the growing period and in the amount of N applied after each cut. Tillers died faster after a 6-weekly growing period than after a 4-weekly period. Some plants were far more affected than others, often resulting in the complete death of plants and thus in open spaces in the sward. Shading experiments suggested that plant deaths resulted from mutual shading. Small plants are shaded by taller ones and have a lower reserve content and a therefore higher death rate. High cutting frequencies or low N application rates could prevent open spaces from appearing or could be used to rehabilitate an open sward provided it was not yet infested with unwanted species. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Pattern of Autumn tillering in a Grasslands 4708 tetraploid hybrid ryegrass sward following two heights of mowing.

Abstract Herbage mass,light interception,and ryegrass tiller dynamics were measured in a tetraploid hybrid ryegrass sward for 8 weeks after cutting to 1–2 cm and 5–6 cm during the late autumn. In both treatments the density of ryegrass tillers increased in the first 2 weeks after cutting and then subsequently declined after the canopy reached full light interception.Tiller density was greater with 1–2 cm cutting as a result of a higher tiller appearance rate in the first 2 weeks after cutting.Tiller death was not significantly affected by cutting height.Ryegrass regrowth mass came mainly from the recovery of tillers present at the time of defoliation,because newly emerged tillers were considerably smaller than the older tillers.

The effects of variety, cutting interval and nitrogen application on the morphology and development of stolons and leaves of white clover

AbstractSix varieties of white clover, each grown with perennial ryegrass, four intervals between cuts and two levels of applied nitrogen in all combinations, were compared in a field experiment during the first 27 months after sowing. Information about yields, crop fractions, heights and ryegrass tillers has been presented in an earlier paper (Wilman and Asiegbu, 1982). The present paper is concerned with the more detailed studies of white clover, which help to explain the yield results and contribute to the understanding of the response of this species to management when grown in competition with grass.Increasing the interval between harvests increased the length of clover stolon per unit area of ground and increased stolon diameter, petiole length, weight per leaf and number of leaves harvested as a proportion of the number present in the sward while only slightly reducing the rate of leaf emergence, helping to explain the positive effect of increasing the interval on clover yield noted in the earlier paper. During regrowth, successive leaves had longer petioles and the length of individual petioles increased beyond the stage at which the leaflets were fully opened. Weight per leaf in clover increased considerably from April to June and declined to below the April value by October. It was shown that weight per leaf can be greatly increased by increasing the interval between harvests without reducing the number of leaves harvested per unit area per year. The stolon length measurements provided some support for the view that medium large‐leaved varieties of white clover can with advantage be defoliated rather less frequently than small‐leaved varieties. Stolon length was less adversely affected by applied N in the medium large‐ than in the small‐leaved varieties. The small‐leaved varieties had thinner stolons than the medium large‐leaved varieties but about twice the stolon length when no N was applied, and a relatively high proportion of leaves which escaped defoliation. The application of N reduced stolon diameter, increased petiole length and had little or no effect on weight per clover leaf.

Tiller Length vs. Tiller Weight: Applications to Plant Growth Studies

Tiller Length vs. Tiller Weight: Applications to Plant Growth Studies

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.

The effect of stage of growth on the rate of drying of cut grass at 20°C

AbstractThe drying of Italian ryegrass (RvP) tillers under controlled conditions at three stages of growth is described. The rate of water loss was dependent on tiller morphology as well as on water content. Leaf laminae dried faster than stems and also aided the loss of water from stems. Drying time was shortest for vegetative tillers despite their high water content, and longest for reproductive tillers shortly before ear emergence. The practical implications in relation to haymaking are discussed.

Survivor populations of S23 perennial ryegrass from zero‐grazed and set‐stocked swards

AbstractPerennial ryegrass tillers were collected from intensively used set‐stocked and zero‐grazed leys and from an old permanent pasture, grown on and compared at 30 cm spacing. All swards except the permanent pasture had been sown with cv. S23 and were of known age, ranging from 6 months to 11 years from sowing.Each genotype was scored for date of inflorescence emergence, and subsequently in vitro dry matter digestibility (DMD), D‐value of green leaf and the ratio of leaf dry weight: stem dry weight were determined.Both DMD and D‐value declined significantly in green leaf samples of populations from the older zero‐grazed swards but no significant changes were detected in populations from set‐stocked swards. In set‐stocked populations there was a shift towards later flowering.In zero‐grazed populations there was a consistent increase in the amount of leaf relative to stem with the age of the sward from which the plants were sampled. The survivor plants were more prostrate and leafier and it is suggested that under zero grazing, where cutting was to a uniform height, plants of this form were less severely defoliated and thus at a selective advantage.

GROWTH CHARACTERISTICS OF PERENNIAL RYEGRASS

Mature perennial ryegrass plants in pastures persist through the asexual reproduction of the tiller. Leaves are initiated from the flanks of the tiller stem apex. Generally, two leaves arc growing on a tiller at any one time. New tiller buds may arise from the axils of mature leaves depending on environmental conditions. Flowering results from a physiological change at the stem apex, which then produces a seed head but no further leaves, eventually resulting in the tiller dying. This phenomenon and other environmental changes result in marked seasonal trends in ryegrass tiller .densities. Leaf, tiller, and root production rates are sensitive to light and temperature where nutritional factors are not limiting. Tillering rates also change with stage of regrowth after defoliation. These factors are discussed with reference to their role in determining seasonal trends.

CHANGES IN THE PERENNIAL RYEGRASS COMPONENT OF GRAZED PASTURES

The contribution of perennial ryegrass to pasture production is dependent on the stage of development of the pasture, climate and pasture management. Although variability in the percentage of ryegrass in improved pastures is less than in developing pastures, changes in the ryegrass component in response to different managemcnts can be marked. Tiller counts demonstrated a lower population of ryegrass tillers under rotational grazing by cattle than under sheep. This was increased by changing either from cattle to sheep grazing or by hard set stocking with sheep during spring. Grazing to 3 cm produced more dense ryegrass pasture than grazing to 6 cm. Severity of grazing appeared to be particularly important in dry conditions when grazing below 3 cm is likely to reduce tiller density. A range of management options is therefore available to encourage the perennial ryegrass component, and thus total dry matter production, of improved pasture.

The effect of interval between harvests and nitrogen application on initiation, emergence and longevity of leaves, longevity of tillers and dimensions and weights of leaves and ‘stems’ in Lolium

SummaryThe effects of six intervals between harvests and three levels of N application on the initiation, emergence and longevity of leaves and longevity of tillers of Italian ryegrass and on dimensions and weights of leaves of four ryegrass varieties were studied in the first harvest year in field experiments. Dimensions and weights of leaves and ‘stems’ of the four varieties were recorded on three dates in the second harvest year.The number of leaf primordia on the shoot apex of young Italian ryegrass tillers was increased by N application and seemed to be increased by increasing the period of uninterrupted growth allowed to the parent tillers. The number of leaves which emerged on marked tillers during a 30-week period was approximately halved by increasing the interval between harvests from 3 to 10 weeks, but was not affected by N application. The number of leaves which died on marked tillers was at least doubled by increasing the interval between harvests from 3 to 5 weeks. The second and third leaves to emerge on a tiller had a longer potential life than the first leaf. Increasing the interval between harvests greatly increased the average age of the green leaves in the canopy at the time of harvest.Length and width, but not thickness, of fully expanded green leaf blades were increased by both N application and increased interval between harvests. The effect of applied N in increasing leaf size appeared to be an important reason for the positive effect of N on yield, particularly with the longer intervals. The effect of N in increasing the number of tillers and leaves was important with the shorter intervals. Applied N reduced dry weight per unit volume of plant tissue and increased ‘stem’ length and increased weight and volume of herbage per unit volume of canopy. The area of exposed surface of ‘stem’ seemed too large to be ignored when considering the photosynthetic capacity of the canopy, particularly with the longer intervals.

SEASONAL TILLER POPULATIONS OF GRASS AND GRASSJCLOVER SWARDS WITH AND WITHOUT IRRIGATION

The number of tillers per unit area of pure swards of S23 and S24 perennial ryegrass, S37 cocksfoot, S48 timothy and of a S23 perennial ryegrass/white clover sward, were examined at intervals of 4 weeks during a period of two years. The monthly appearance of new tillers and the death of tillers of S23 and S24 ryegrass and S48 timothy were followed for 15 months. The studies were made with and without irrigation.The number of tillers varied with season through the year. Tiller numbers increased rapidly in late winter or early spring, and then declined until midsummer. Numbers rose again between June and August. This seasonal pattern of tiller numbers was most marked in ryegrass and timothy and least in cocksfoot. The effect of irrigation on tiller numbers was variable, and usually small in relation to the overall seasonal fluctuations in tiller numbers, but dry soil conditions could delay an increase in tiller numbers between June and August. The relationship between seasonal fluctuations in tiller number and root growth of swards is discussed.

THE FREQUENCY AND SEVERITY OF DEFOLIATION OF INDIVIDUAL TILLERS IN SET‐STOCKED SWARDS

Individual tillers of S23 ryegrass, in three paddocks set‐stocked with sheep at widely differing grazing pressures, were marked and studied from 11 July to 19 August, 1966, and observations were made on the frequency and severity of grazing.The uprooting of tillers, and the destruction of others, were major sources of loss of records. It was found that an acceptable measure of the frequency of defoliation could be made by recording three times a week. In a subsidiary experiment it was shown that repeated handling did not affect the DM yield, the number of tillers or the length of green leaf (G.L.L.) of single plants.Despite the extreme differences in grazing pressure, there were no significant differences between paddocks in the daily increase in the G.L.L. of tillers which were not grazed during a short period of intensive recording. In all three paddocks the sheep tended to graze the tillers with the greatest G.L.L. at any one time, and there was evidence of patchy grazing only at the lowest grazing pressure.An increase in grazing pressure resulted in increases in both the frequency and severity of defoliation. Comparisons were made between the product of the frequency X severity of defoliation of individual tillers, and the stocking rate, grazing pressure and herbage consumption on the three paddocks.

THE INFLUENCE OF NITROGEN ON A PASTURE TREATED WITH DALAPON FOR THE SELECTIVE SUPPRESSION OF AGROSTIS STOLONIFERA AND HOLCUS LANATUS IN PERENNIAL RYEGRASS

This experiment confirmed earlier experience that dalapon applied at doses between 2 and 5 lb a.e./ac (2.242 and 5.605 kg/ha) in early July can suppress Agrostis stolonifera and Holcus lanatus growing in perennial ryegrass pasture. The long‐term control of Poa trivialis was not achieved, partly because of a widespread emergence of seedlings shortly after spraying. Dalapon caused a reduction in the total herbage harvested diuring the 14 weeks after spraying, but the yield subsequently increased above that of the unsprayed sward. A substantial increase in the yield of ryegrass occurred. Nitrogen caused a general increase in the yield of herbage and the proportion of ryegrass, but neither N nor dalapon used alone was as efficient in improving yield as their use in combination. Treatment with dalapon resulted in an increase in the number of ryegrass tillers per unit area in the April following spraying, as well as in the yield and ground cover of this species.

THE EFFECTS OF LONG‐TERM STORAGE ON THE VIABILITY OF S23 PERENNIAL RYEGRASS SEED AND ON SUBSEQUENT PLANT DEVELOPMENT

Eight lots of seed of S23 perennial ryegrass which had been artificially dried to different moisture levels and stored for 20 years were tested for germinating capacity, and the effects of long‐term storage on subsequent plant development were studied. The results of the germination tests indicated a continuation of the downward trend in viability previously reported. Observations on the derived mature plants revealed no difference between lots in general growth habit; a few seedlings showed symptoms of some retardation in growth but most plants manifested the high tillering and prostrate growth typical of S23 perennial ryegrass. Pollen fertility was markedly reduced in 38% of all the plants sampled. The seed‐setting capacity was affected to an even greater extent, 44% of the plants giving seed‐set values decidedly below those obtained for plants grown from new seed. Where pollen fertility had been much reduced, seed‐setting also was usually low, but there were some instances of satisfactory pollen fertility associated with a low seed set.

Effects of gibberellic acid, indole-acetic acid, coumarin and perloline on perennial ryegrass (Lolium perenneL.)

Summary The effects of several growth substances on growth and tillering of perennial ryegrass were investigated. Gibberellic acid produced initial elongation resulting in taller plants, followed by total reduction due to reduced rate of tillering, as reported by other workers. At the rates used, there was no promotion of tiowering, either in the sense of replacement of vernalization or daylength requirement, or in earliness. Inbreeding depression of green weight was not removed by gibberellic acid, but there were some responses, differing with the genotype. Coumarin was found to have little effect on growth or tillering. The main effect of indole-acetic acid was the rooting promotion of derooted cuttings. Perloline had a growth-inhibiting effect, not reported previously. Interactions were found between the treatments and genotypes.

The influence of time of tiller origin and nitrogen level on the floral initiation and ear emergence of four pasture grasses

Summary A study was undertaken for perennial ryegrass, Italian ryegrass, cocksfoot, and timothy, of the floral initiation, ear emergence, leaf number at ear emergence, and percentage of fertile tillers with dates of origin between May 1958 and February 1959. The influence of two levels of nitrogen was examined. Despite large ranges in their time of origin, winter and earlyspring tillers of perennial ryegrass, Italian ryegrass, and timothy all initiated floral primordia within a relatively short period. Ear emergence followed the same pattern. Mean leaf number at ear emergence decreased with tillers of later origin to minima of 6 for perennial ryegrass, 7 for Italian ryegrass, 9 for cocksfoot, and I+ for timothy. In cocksfoot and timothy the percentage of fertile tillers was high only for those formed before mid winter, whereas in perennial ryegrass and Italian ryegrass the percentage remained high even for tillers formed up to late spring. High nitrogen promoted earlier floral initiation and ear emergence, and a greater percentage of fertile tillers. The effect was most marked in cocksfoot. The majority of heads emerged during the 3–4 week period after the first recorded ear emergence in each species. The heading of perennial ryegrass was inhibited by a controlled high day/night temperature of 90°F/70°F over a 7-week period.