The effect of light intensity after anthesis on dry matter distribution and seed yield of Lolium perenne L.

The effect of light intensity after onset of anthesis on dry matter distribution, water soluble carbohydrate (WSC) concentration and seed filling in Lolium perenne was investigated in a pot experiment. Spaced plants of five clones were brought to flowering and exposed to four light intensities (24%, 57%, 100%, 115% of natural light) from 7 days after onset of anthesis onwards. The two oldest flowering tillers (i.e. the main and the first tiller) were separated from the rest of the plant and dissected after a seed-filling period of 450°Cd (temperature sum counting from 7 days after onset of anthesis). Their stem dry weight and WSC concentration were reduced at the lowest light intensity. WSC amount was more reduced in the first, younger, tiller. Seed yield per ear of the main tiller was reduced by 14% because seed set and average seed weight were lower at the 24% light intensity. Seed yield and seed number per ear of the first tiller were lowered by 21% and 17%, respectively, at the 24% light intensity, but average seed weight was not. The relative contribution of the seeds to total tiller weight was about 20% and was similar for both tillers and all light intensities. WSC concentration and WSC amount in the stem + rachis were reduced only at 24% light in the main tiller and at 24% and 57% light in the first tiller. It is inferred that seed yield was not limited by assimilate availability, but by the ability of the seeds to utilize fully the abundantly available reserves in the stem. The tiller can support seed yield under a wide range of tight intensities.     

Nitrogen studies in Lolium perenne grown for seed III. The effect of nitrogen and water stress

The effects of water and nitrogen (N) availabilities and their possible interactions on the seed yield and yield components of S23 perennial ryegrass grown in pots in the glasshouse were investigated. Increasing the N fertilizer from 0 to 5 g per pot more than doubled the seed yield but no further increase in seed yield was found by increasing N fertilizer from 5 to 10 g per pot. The main effect of increasing water availability was to increase both seed and straw yield. When N had been applied, accumulated evapotranspiration was linearly related to seed and straw yield. The component of yield having the greatest effect on yield was the number of fertile tillers and, although both N and water availability affected this component, N had the larger effect. Implications of these responses are discussed in relation to the potential yield of the crop and to the field situation.     

Nitrogen studies in Lolium perenne grown for seed I. Level of application

In field trials in 1971–73, perennial ryegrass cv. S23 and S24 were given up to 200 kg ha^?1 nitrogen (N) and dry weight, seed yields and seed yield components measured. Optimum levels of applied N ranged from 80 kg ha^?1, where livestock had grazed the crop in the establishment year or where residual N levels were about 70 kg ha^?1, to 120 kg ha^?1 where residual N was low. Application of more than 120 kg ha^?1 did not increase yields further because of increased lodging and increased production of vegetative tillers. Seed set was 37–55% in S24 and 25–29% in S23 and was decreased by lodging.     

Nitrogen studies in Lolium perenne grown for seed. II. Timing of nitrogen application

The effects of applying nitrogen at different growth stages to S24 and S23 perennial ryegrass grown for seed were investigated in a series of field experiments from 1971 to 1976. These varieties of ryegrass were found to be insensitive to timing of nitrogen application from apex initiation to the stage when ears first emerged. However, if nitrogen application was delayed until about 30% or more of the ears had emerged, yields were lower compared with earlier applications, this effect being significant when nitrogen was delayed until 70–80% ear emergence because of a decrease in both numbers of fertile tillers and number of seeds per unit area. No advantages were found for splitting nitrogen applications between apex initiation and ear emergence.     

The effect of the growth regulator paclobutrazol (PP333) on the growth, development and yield of Lolium perenne grown for seed

Application at spikelet initiation of the growth retardant paclobutrazol (PP333) at a rate of 2.0 kg a.i. ha⁻¹ increased the seed yield of perennial ryegrass cv. S24 from 139 to 180 g m⁻² in 1981, and from 111 to 256 g m⁻² in 1982. Yield increases were associated with an increased production of fertile tillers in both years and with an increased number of seeds per spikelet in 1982. Other yield components were not changed. Seed yield increased with increasing PP333 application rate in both years. No significant yield difference was recorded between application at spikelet and floret initiation in 1981.
Lodging was prevented completely by the 2.0-kg rate, delayed until after anthesis by the 1.0-kg rate and began before anthesis with the 0.5-kg rate. PP333 reduced stem internode length and strengthened the base of the stem; total stem dry matter (DM) was reduced, but root DM accumulation was increased at all rooting depths. Leaf area duration was significantly increased in both years.
Vegetative regrowth after seed harvest was not significantly reduced by PP333 application, but soil residual properties were demonstrated.     

Nitrogen studies in Lolium perenne grown for seed. IV. Response of amenity types and influence of a growth regulator

In field trials in 1979–81, perennial ryegrass cultivars Royal and Majestic (amenity) and Morenne (agricultural) produced maximum seed yields at levels of applied N ranging from 40 kg ha⁻¹ to 160 kg ha⁻¹. Available soil N levels were estimated at 55 kg ha⁻¹; hence maximum seed yields were obtained at total nitrogen levels of 95–135 kg ha⁻¹ in Royal, 95–215 kg ha⁻¹ in Morenne, and 175–215 kg ha⁻¹ in Majestic.
Applied N at rates above 120 kg ha⁻¹ either reduced or did not significantly increase seed yield, decreased seed numbers per unit area and decreased spikelets per tiller and seeds per spikelet.
The use of a growth regulator increased seed yields by preventing lodging, but did so irrespective of nitrogen application rate. It is suggested that failure to increase seed yield at high N rates is a result not of poor pollination because of lodging, but seed abortion as a consequence of competition for assimilate supply by secondary vegetative tillers.     

The use of growth regulator RSW0411 in seed crops of Lolium perenne L.

Field trials were conducted in 1985 and 1986 to assess the effects of the growth regulator RSW0411 on a Lolium perenne L. (perennial ryegrass) seed crop. Applications were made at spikelet and floret initiation, and at 1, 2, 3 and 4 kg active ingredient ha⁻¹.
Seed yield increases in 1985 were associated with increased reproductive tiller numbers and seed numbers, but in 1986 there were no seed yield responses.
Lodging was less severe in 1986, and there was less secondary filtering during seed maturation. In 1985, fertile tiller numbers were lower in control plots at harvest. These results are discussed in relation to the seasonal disparity in seed yield response.
RSW0411 application significantly decreased culm lengths by shortening the basal internodes, and this effect was greater with higher application rates. Stem width was increased in 1985 at the base and middle of the stem, and earlier applications increased the basal width by more than later applications.
Germination was not affected by RSW0411 treatment, except when applied at 4 kg active ingredient ha⁻¹ in 1985, when there was a small decrease. This was related to a low 1000-seed weight, and is discussed in relation to seed maturity at harvest.     

A simultaneous effect of selfing and Epichloë endophyte on forage,seed yield and turf characteristics of perennial ryegrass (Lolium perenne L.)

Ryegrass (Lolium perenne L.) is a putative turf and forage plant characterized as mainly outcrossing in which the extent of self‐fertilization and its consequences has not been investigated. In this study, selfed and half‐sib family seeds were obtained from ten clonally propagated ryegrass plants among which two were endophyte‐free (EF) and eight were endophyte‐infected (EI). Then, 20 seed populations plus two commercial varieties of Speedy and Vigor were sown and evaluated in a biennial experiment for their turf and forage characteristics. Selfing caused significant inbreeding depression for plant fresh and dry weight and leaf length and width in the first year for both EI and EF genotypes. In the second year, only leaf length remained depressed among these characters. Also, for the most growth, turf and reproductive traits, EI populations showed less depression. The presence of endophyte in self‐pollinated populations made an increasing effect for the number of seed per spike and days to heading, although seed weight was reduced. Some of the populations derived from self‐pollination and infected with fungal endophyte including S9 and S10 were even superior to the two commercial varieties in terms of both seed production and turf characteristics. However, for seed‐related characteristics including number of spikes per plant, seed weight and seed yield, EF populations including Speedy and Vigor were more reproductive than EI populations. It is concluded that selfing may increase the discrimination between EI and EF ryegrass plants because endophyte infection may mitigate the negative consequences of inbreeding depression in prone populations.     

The influence of ethofumesate on the growth and development, chlorophyll and nitrogen content of Lolium perenne L.

Pot experiments and a hand-weeded field trial were carried out to investigate the direct effect of ethofumesate on the growth and development of Lolium perenne cv. S24.
In the field trial, ethofumesate was applied in autumn as Nortron 20% ec formulation in a volume of 2001 ha^-1 at rates of 0, 1 or 2 kg a.i. ha^-1. Treatments had no direct effect on yield in the following summer. In both the field trial and pot experiments there was initial growth suppression in the form of a reduction in shoot dry weight, lamina dry weight, tiller number per plant and plant height. However, ethofumesate increased the chlorophyll and nitrogen contents of L. perenne laminae, but only when available soil nitrogen was not limited.
It is concluded that ethofumesate can increase the yield of L. perenne by suppressing weed competition, but there is no evidence of the herbicide directly increasing the growth or yield of cv. S24.     

The winter hardiness of Festuca rubra, Holcus lanatus and Agrostis spp. in comparison with Lolium perenne

Preliminary experiments were conducted to assess the winter hardiness of representative cultivars or populations of Festuca rubra, Holcus lanatus and Agrostis spp. in comparison with a hardy (Premo) and a susceptible (Grasslands Ruanui) cultivar of Lolium perenne. Two controlled-environment tests and a field experiment including two cutting and two fertilizer managements are reported.
Grasslands Ruanui and H lanatus suffered most damage in all tests. In the controlled-environment experiments, Premo was at least as hardy as the F. rubra and Agrostis cultivars but in the field Premo was more susceptible. Spring growth of Premo was affected more by the cutting and fertilizer managements applied the previous summer and autumn than was spring growth of F. rubra or Agrostis spp.
It was concluded that, whereas use off. F. rubra or Agrostis spp. should not be limited by fears of winter damage, poor winter hardiness may limit the value of H. lanatus for hill and upland reseeding.     

The effects of management and plant variety on the composition, vertical structure and stock-carrying capacity of Lolium perenne/Trifolium repens pastures

The effects of sheep grazing, with or without a 7-week rest period before ear emergence, on species balance in four perennial ryegrass/white clover swards were assessed.
Swards of an early (Aurora) or a late (Melle) flowering ryegrass were grown with either a small-leaved (Kent) or a medium-leaved (Milkanova) clover.
The clover lamina, expressed as a proportion of the total lamina mass, was greater with Kent than Milkanova. This proportion was not changed by resting the Aurora (earlier rest) swards, but was increased by resting the Melle (later rest) swards. A greater proportion of the clover lamina mass was near the top of the canopy in the Milkanova than in the Kent swards, and during the summer than in spring or autumn. The densities of clover growing points were greater in the Kent than the Milkanova swards and were increased by the late rest period. This effect persisted over the winter.
Stocking density was higher on the Kent than the Milkanova swards. The effects of the two rest periods, and the variety combinations, on pasture composition are interpreted as being principally a result of the differences in temperature between the earlier and later rest periods and of the different relationships between temperature and the growth of ryegrass and clover. Varietal characteristics, such as the vertical distribution of laminae, were also shown to be important.     

The effect of the weather on the drying rate of cut diploid and tetraploid perennial ryegrass (Lolium perenne L.) and diploid hybrid ryegrass (Lolium perenne×L. multiflorum)

The drying rate of cut diploid and tetraploid perennial ryegrasses ( Lolium perenne L.) and a diploid hybrid ryegrass ( Lolium perenne × L. multiflorum ), and associated meteorological characteristics, were studied in the field for three successive years: 1988, 1989 and 1990. Meteorological elements measured were: air temperature (at 0·1 in and 1·5 in height), dew point temperature (at 1·5m height), temperature within the grass sward, grass surface temperature, global radiation and wind speed (at 2 in height).
Apart from the weather, the drying depended on the grass species and the yield. Hybrid ryegrass had a lower initial moisture content at cutting in the morning than perennial ryegrass. Also, the hybrid ryegrass dried faster than the perennial ryegrass. Within the same varieties a low yield dried faster than a high yield. Frequent tedding did not influence the rate of drying. The temperature within the grass swath approached the air temperature at 1·5 m. The grass surface temperature was greatly affected by global radiation. Increasing wind speed had an adverse effect on the drying rate of grass.     

The effect of density on tuber yield in plants grown from true potato seed in seed beds during two contrasting seasons

The production of potatoes from true seed was studied in direct-sown seed beds during both winter and summer seasons in Lima, Peru. After emergence, seedlings were thinned to give 6, 12, 24, 48 or 96 plants per m². In all five density treatments plants were arranged in a square configuration. In both seasons, increasing plant density significantly increased total tuber number as well as tuber weights in the grades 1–5 g, 5–20 g and 20–40 g. The yield of tubers larger than 40 g was similar in all densities. In the warm summer season, tuber number was significantly reduced and mean tuber weight was 56% greater compared with that in the winter season. The potential of producing consumer potatoes from true seed in seed beds in warm climates is discussed.     

Effect of three clover varieties on growth, 15N uptake and fixation by ryegrass/white clover mixtures at three sites in Wales

Grass and clover production and nitrogen cycling were compared in 1983 and 1984 at three sites: an upland peaty gley and upland and lowland brown earths. The clover varieties Olwen and S184 were compared in 1983 and S100 and S184 in 1984. Ammonium and nitrate sources of ¹⁵N were used to measure nitrogen recovery from fertilizer and soil, nitrogen fixation and nitrogen transfer from clover to grass. Acetylene reduction was measured once, in 1983, but isotope dilution was used in both years.
Olwen clover produced more dry matter and took up more ¹⁵N than S184. Olwen fixed more nitrogen than S184 over the whole season, as measured by ¹⁵N isotope dilution. Companion grass took up more soil nitrogen when growing with S184 than with Olwen. The clover variety S100, tested at the lowland site in 1984, caused no significant variations in dry matter accumulation or N fixation.
In the dry 1984 season, grass dry matter accumulation and ¹⁵N uptake were less than in 1983, and plants actually lost total nitrogen from their roots to the soil. Fixation rate varied more in 1984 than in 1983. Nitrogen transfer from clover to grass was detected by isotope ratio differences in 1983, and by total N differences in 1984.
Site differences were dominated by the greater dry matter accumulation of Olwen in the lowland in 1983, but in that year there was also increased dry matter accumulation and increased ¹⁵N fertilizer uptake, but less nitrogen fixed on the mineral upland site than on the peat soil.
Whether ¹⁵N was given as ammonium or nitrate made little difference in these experiments.     

The use of asulam to control Bromus sterilis in ryegrass crops grown for seed

Asulam applied in April 1981 and 1982 gave good control of established plants of Bromus sterilis growing in Italian and perennial ryegrass crops grown for seed. Doses of 1–3 kg a.i./ha reduced numbers of weed inflorescences by 65–90%. The results also showed that there was no effect on crop heading and further suggested that seed yield had not been reduced. Two pot experiments also indicated the efficacy of asulam at 0·5-2 kg a.i./ha applied pre-emergence and further study of such treatment in the autumn during the establishment of a ryegrass seed crop is warranted.     

The effect of autumn fungicide application on spring dry matter accumulation in perennial ryegrass cv. S24

Fungicide applied to plots of perennial ryegrass cv. S24 in the autumn of 1981 significantly increased tiller number and total dry matter accumulation in February and March of 1982. However, fungicide application in the autumn of 1982 failed to increase tiller number or dry matter accumulation in the spring of 1983. It is suggested that fungicide application in autumn 1981 prevented the death of tillers caused by fungal attack after snow covered the plots in December 1981.     

The effect of Rhizobium spp. inoculation on seed quality of bean in Turkey

Rhizobium spp. (local isolate) was used to inoculate three bean (Phaseolus vulgaris L.) varieties; Akman 98, G?ynük 98 and Sehirali 90, in a factorial field experiment. The objective of the experiment was to study effect of inoculation on seed yield, protein range, seed weight, non-soaker capacity and hydration index. Rhizobium spp. inoculation and nitrogen fertilizer significantly increased characters tested. This study revealed that inoculation with Rhizobium spp. improved seed quality.     

The effect of two planting dates on the physiological age and yielding potential of seed potatoes grown in a warm temperate climate in Argentina

Summary The effect of two planting dates upon the physiological age of seed tubers, measured by their incubation period, and their yielding potential was studied during a three-year period with two medium-early and one medium-late cultivar. Although seed tubers of the December planting were physiologically significantly younger than those obtained from the November planting in two of the three seasons studied, no reliable effect upon tuber yield was found. Reasons for this lack of relation are discussed. The accumulated day-degrees above 17°C (daily mean temperature) during the bulking period of the seed crop modified the incubation period of the tubers clearly.

---

Zusammenfassung Der Einfluss zweier Pflanztermine auf das physiologische Alter von Pflanzkartoffeln und ihr Ertragspotential wurde w?hrend einer Dreijahresperiode an zwei mittelfrühen Sorten, Spunta und Kennebec, und einer mittelsp?ten Sorte, Bonaerense la Ballenera MAA, in warmer gem?ssigter Klimazone in Argentinien geprüft. Saatbest?nde aus November- und Dezemberpflanzungen von 1979, 1980 und 1981 wurden im November 1980, 1981 und 1982 in vergleichenden Ertragsversuchen gepflanzt. Das physiologische Alter der Knollen wurde bei der Pflanzung durch die Inkubationsperiode (Claver, 1973, 1975) gemessen. Abb. 1 zeigt die meteorologischen Daten der vier Vegetationsperioden. Es ergaben sich signifikante Unterschiede im physiologischen Alter zwischen den Sorten und den Pflanzterminen (Tab. 1). Bei Lagerung der Saatkartoffeln in Mieten im Feld beschleunigte sich das physiologische Alter (Tab. lc). Die Gesamtknollenertr?ge schwankten zwischen den Sorten in 1980/81 und 1982/83 (Tab. 2a und 2c), es ergaben sich jedoch keine signifikanten Unterschiede zwischen Pflanzgut der beiden Pflanztermine, obwohl sich zwischen beiden Pflanzterminen Unterschiede im physiologischen Alter ergaben. Der Gesamtknollenertrag war 1982/83 am h?chsten (Tab. 2c), obwohl die Pflanzknollen physiologisch die ?ltesten waren. Es ist unwahrscheinlich, dass eine hohe prozentuale Infektionsrate mit PLRV und PVY der Pflanzknollen von Spunta und Kennebec aus der Dezemberflanzung den Einfluss des physiologischen Alters auf den Ertrag derart überdeckte, dass keine signifikanten Unterschiede mehr gefunden werden konnten (Abb. 2). Weil die Unterschiede im physiologischen Alter innerhalb einer Sorte jedoch klein waren, waren andere ertragsbestimmende Faktoren offensichtlich wichtiger als die Unterschiede im Alter. Die akkumulierten Tagesgrade über einer t?glichen Temperatur von 17°C w?hrend der Periode des Knollenansatzes hatten eine klare ?nderung der Inkubationsperiode zur Folge.

---

Résumé L'effet de deux dates de plantation sur l'age physiologique de tubercules de semence et sur leur rendement potentiel a été étudié durant une période de trois années avec deux variétés demi-hatives, Spunta et Kennebec, et une demi-tardive, Bonaerense la Ballenera MAA, cultivées dans un climat chaud d'Argentine. Les plants récoltés en novembre et décembre des années 1979, 1980 et 1981 ont été plantés en novembre 1980, 1981 et 1982 selon des essais comparables de rendement. L'age physiologique des tubercules était évalué à la plantation par la période d'incubation (Claver, 1973, 1975). Les relevés météorologiques pour les quatres saisons sont donnés dans la fig. 1. On observait des différences significatives dans l'age physiologique entre les variétés et les dates de plantation (tabl. 1). Quand les tubercules de semence étaient conservés en silo au champ, l'age physiologique était avancé (tabl. lc). Le rendement total en tubercules était différent entre variétés pour 1980/81 et 1982/83 (tabl. 2a et 2c) mais il n'y avait pas de différences significatives entre les plants des deux dates de plantation bien qu'il y ait des différences significatives dans leur age physiologique. Le rendement total en tubercules était plus élevé en 1982/83 (tabl. 2c) malgré des tubercules de semence physiologiquement plus vieux. Il est peu probable que le taux important d'infection par les virus de l'enroulement et Y des semences de Spunta et Kennebec observé de l'age physiologique des plants sur les rendements, ceux-ci ne présentant aucune différence significative (fig. 2). De plus, parce que les différences d'age physiologique des semences au sein d'une variété sont-faibles, d'autres facteurs déterminants que le rendement doivent avoir été plus importants que la différence d'age. Le cumul jour-degrés au-dessus de la température journalière de 17°C durant la période de tubérisation des tubercules de semence modifie sensiblement la durée d'incubation des plants (fig. 3).

     

The contribution of perennial ryegrass (Lolium perenne L.) breeding to whole pasture productivity under dairy cattle grazing in New Zealand. 1. Variation in yield,nutritive value and persistence-related traits

Perennial ryegrass (PRG, Lolium perenne L.) breeding effort in New Zealand (NZ) has increased since c. 1990, resulting in greater functional trait diversity (e.g. heading date, ploidy, and associated Epichloë endophyte strain) in commercial products. This study quantified the variation, associations and interactions in dry matter (DM) yield, nutritive value and persistence-related traits among commercial cultivar-endophyte combinations released between 1973 and 2012, as a basis for assessing gains in value being delivered to the pasture-based livestock industries. Twenty-four or 28 combinations were compared over 3 years in two trials in each of two regions: Waikato in northern NZ (dryland), and Canterbury in central eastern South Island (irrigated). Cultivar-endophyte combinations were sown in mixtures with white clover, and pastures were intensively grazed 8–11 times per year by dairy cows. Principal Component Analysis identified 4 distinct clusters for the DM yield variables and for metabolisable energy (ME) content in each of the four trials. A broadly-adapted group of three late-season flowering, AR37-infected diploids with NZ and Spanish breeding backgrounds dominated the highest-yielding clusters. Tetraploids dominated the high ME content clusters. Interactions with region were observed throughout the data set: the strongest of these was driven by endophyte strain effects in Waikato. High-yielding cultivar-endophyte combinations in these trials were also generally high-yielding in the standard cultivar merit testing system operated in New Zealand, as interpreted via the DairyNZ Forage Value Index. However, alignment was poorer for medium- and lower-yielding cultivar-endophyte combinations. Several implications for forage evaluation methods and end-user industries are identified.