SPRING GROWTH OF PERENNIAL RYEGRASS AND COCKSFOOT

Preliminary results are given of experiments in progress to investigate the onset of spring growth and to compare spring growth rates in early- and late-types of perennial ryegrass and cocksfoot.     

THE EFFECTS OF DIFFERENT LEVELS OF NITROGEN FERTILIZER ON THE YIELDS OF VARIETIES OF PERENNIAL RYEGRASS AND COCKSFOOT

Little is known about the possible differential responses to Nitrogen fertilizer in varieties within grass species. Two trials were conducted to study interactions between varieties and level of N. The dry-matter yields of 3 varieties of perennial ryegrass were compared in 4 cuts/yr at 3 levels of N fertilizer. Four cocksfoot varieties under the same cutting management were compared at 2 levels of N. In a total of 20 comparisons, the variety effect was significant on 10 occasions, and the N effect significant in all 20 sets of data. The interaction of variety and N level was significant in only one case suggesting that all varieties in each trial responded similarly to increasing levels of N fertilizer.     

THE NITROGEN AND PHOSPHORUS FERTILIZATION OF PERENNIAL RYEGRASS GROWN AT HIGH ALTITUDES IN KENYA

The effects were studied of nitrogen and phosphorus fertilizers on the production of perennial ryegrass at high altitudes in Kenya. N had little influence on production during establishment but increased it markedly during the second and third years. The effect of P was less and was related to the amount of N applied. The response to applied N in terms of dry matter production, and the recovery of the N applied, compared favourably with data from trials elsewhere. It is apparent from the results that temperate grasses can be productive at high altitudes in Kenya and provide a considerable potential for pasture production.     

THE BEHAVIOUR OF COCKSFOOT AND PERENNIAL RYEGRASS FAMILIES FROM WESTERN FRANCE GROWN AT ABERYSTWYTH

Families of Dactytis g/omerata and Lolium perenne derived from ripe inflorescences collected in western France over a range of nearly 7° of latitude were grown at Aberystwyth, 52° N lat. Their growth was examined to determine whether latitude and the habitat of the collected families affected the dates of ear emergence, phml form, and height of the flowering shoots when the grasses were grown at Aberystwyth, Ear emergence was found to be delayed as the latitude of the seed source increased, irrespective of the year of sowing, or, in the case of cocksfoot, irrespective of whether the plants were in their first or second harvest year.
Plant growth-form and panicle height were recorded only for the cocksfoots, and the results indicate that they were influenced by habitat and that they reflected the intensity of biotic control that had operated.
The families derived from meadows or road verges tended to contain a higher percentage of erect tall types. When, however, the seeds came from grazed orchards or pastures, there were few or no erect plants, but many with a more or less prostrate habit and shorter panicles.     

THE DIGESTIBILITY OF THE LEAVES AND STEMS OF PERENNIAL RYEGRASS, COCKSFOOT, TIMOTHY, TALL FESCUE, LUCERNE AND SAINFOIN, AS MEASURED BY AN IN VITRO PROCEDURE

Determinations of the in vitro digestibilities of leaf-blade, leaf-sheath and stem fractions of the grasses cocksfoot, perennial ryegrass, timothy and tall fescue and of the leaves and stems of lucerne and sainfoin have shown that all parts of the plant have a high digestibility at early stages of growth. With increasing maturity, however, the digestibility of the stem falls off at a much faster rate than that of the leaf; in grasses, leaf-sheath digestibility declines at an intermediate rate. The decline of digestibility is associated with a reduction in the content of water-soluble and protein constituents in the plant, and with a reduction in the digestibility of fibre. This may provide a biochemical basis for the selection of forage plants of high digestibility in plant-breeding studies.     

THE CONSUMPTION OF PERENNIAL RYEGRASS AND RED CLOVER BY GRAZING LAMBS

Groups of six-month old lambs, which were either experienced or inexperienced grazers, strip-grazed swards of S24 perennial ryegrass or Hungaropoly tetraploid red clover, at daily herbage allowances of 20 or 40 g OM/kg LW, in late August and September. The swards were similar in N content, but the weight of standing crop, and its digestibility, were higher on grass than on clover. Estimates of herbage intake were made in two successive periods of 19 days. Intake (g OM/kg LW) was lower at low than at high allowance (by 22% and 28% in periods I and II). and experienced grazers ate more than inexperienced animals (by 27% and 22%). Intakes on clover were 28% higher than on grass in Period I, but in Period II the difference was not significant.     

THE ABSORPTION OF PHOSPHATE AND CALCIUM FROM DIFFERENT DEPTHS IN SOIL BY SWARDS OF PERENNIAL RYEGRASS

A method for measuring the depth in soil from which plants absorb nutrients is descrihed. Radioactive tracers are injected at different depths and when allowance is made for any variations in the extent to which the added tracer is diluted hy labile ions in the soil at each depth the relative quantities of nutrient taken up from different depths can be calculated. Results obtained with perennial ryegrass swards of contrasting age indicated that the nptake of P and Ca always occurred predominantly from within the top 12.5 cm of soil. Apart from the initial few months of a sward's life, the proportion of both elements absorbed from different depths for a whole growing season varied little with age of sward up to 3^1/2 years. Considerable changes in the relative contrihution of different depths of soil to uptake occurred within a season; the extent of uptake from the surface layers was primarily influenced by variations in soil-water content and the application of fertilizer to this region.     

THE PRODUCTION OF DRY MATTER BY SWARDS OF PERENNIAL RYEGRASS, DIFFERING IN AVERAGE AGE OF FOLIAGE

Leaves of different ages were removed 7 times between June and October. Each defoliation was timed to match the appearance of successive leaves on each tiller. The removal of leaves at progressively younger stages reduced total production above ground, but the most severe treatment, the removal of all expanded leaves repeatedly, still produced about 75% as much as the least severely defoliated sward. Clipping with shears 3 times reduced yield as much as removing all expanded leaves 7 times. A crop allowed to grow untouched apparently produced more than any defoliated treatment, but this may have been an artefact.
The lower production following increasingly drastic defoliation was not associated with reduced concentrations of nitrogen or potassium in the foliage removed, or in the crop left behind. The total quantity of these elements recovered in the crop was greatest in those treatments where least dry matter was produced. Explanations for the results depend on the capacity of swards of predominantly young leaves to assimilate carbon more rapidly than those containing old and senescent tissue.     

THE GROWTH OF VARIETIES OF PERENNIAL RYEGRASS IN THE SEEDING YEAR

These studies showed that in the first autumn the capacity for soil establishment of different varieties of perennial ryegrass was connected with seed size. On one of two experimental fields, shoot production in the early stages was found to be positively correlated with seed size. The rate of tillering was initially similar for all varieties, but by January or February, the pasture varieties had the highest tiller numbers. However, shoot weights at this time differed very little from variety to variety. Tillering virtually ceased during December and January and started again in February.
The yields obtained from the five varieties in spring, when cut with an autoscythe. differed greatly despite the similar shoot weights of individual plants. It is suggested that the spring growth in pasture varieties is largely below cutting level.     

THE EFFECT OF SEED WEIGHT AND DEPTH OF SOWING ON THE EMERGENCE AND EARLY SEEDLING GROWTH OF PERENNIAL RYEGRASS (LOLIUM PERENNE)

Seed of S24 perennial ryegrass of two weight ranges, 0.9–2.1 and 2.5–3.6 mg, were sown in soil at depths of 1.25, 2.5, 5.0 and 7.5 cm. Seedling growth was studied during the 3 weeks following germination.
Seeds of both weight ranges germinated equally well at soil depths down to 7.5 cm. However, the number of shoots that emerged was reduced as the sowing depth increased. At similar depths of sowing, seedlings from the heavy seed were heavier and developed more leaves and tillers than those from light seed. Deeper sowing reduced seedling weight and the rate of leaf- and tiller-production. After emergence, the relative growth rates of the seedlings which grew from seed of both weight ranges were similar at those depths of sowing which permitted the highest proportion of emerged shoots to seeds sown. This indicates that the weight advantage gained by the seedlings that developed from heavy seed during their non-photosynthetic stage of growth was maintained, and was not increased by a greater relative growth rate after photosynthesis began.
The implications of the findings are discussed in relation to plant breeding, commercial seed production and sward establishment.     

EFFECTS OF METHOD OF ESTABLISHMENT ON TALL FESCUE AND ITALIAN RYEGRASS MIXTURES IN THE FOLLOWING YEAR

Tall fescue and Italian ryegrass mixtures react differently to management in the year of sowing. The decrease in yield of tall fescue and the increase in growth of red clover, caused by the use of a cover crop, was still evident in the following year. In both the spring grazing and total yield of the first harvest year, the Italian ryegrass/ white clover mixture was better than the tall fescue/white clover mixture when a cover crop was used. The reverse trend was recorded when the grass plus clover was sown without the cereal. In general, the addition of red clover to the tall fescue/ white clover, or Italian ryegrass/white clover mixture, increased the yield, but the magnitude of the increase was modified by management during establishment. The increase in total herbage yield and the reduction of white clover growth due to nitrogen application were both related to management in the year of sowing. Consideration should thus be given to method of establishment in the assessment of herbage seeds mixtures.     

THE SIGNIFICANCE AND CONTROL OF POA TRIVIALIS IN RYEGRASS PASTURES

A review of published information on the growth and productivity of Poa trivialis in relationship with perennial ryegrass is presented. The available evidence indicates that P. trivialis is usually out-yielded by ryegrass, particularly under drought and infertile soil conditions. In addition, the quality and seasonal distribution of the yield is often of questionable value. It would therefore appear that P. trivialis can be considered an undesirable species in most intensively managed ryegrass pastures. Preliminary results from competition studies between F. trivialis and S23 perennial ryegrass confirm that the replacement of ryegrass by P. trivialis leads to a lowering of productivity. The latest control measures for preventing the invasion and/or removal of P. trivialis from ryegrass pastures are given, based largely on the use of selective herbicides.     

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.     

VARIATION IN HEADING DATES OF PERENNIAL RYEGRASS CULTIVARS AS INFLUENCED BY SPRING AND EARLY SUMMER TEMPERATURES

Ear emergence data for 9 cultivars of perennial ryegrass have been recorded in Northern Ireland at the Plant Testing Station, Crossnacreevy, each year since 1967. These data show that while early spring (March-April) temperatures have a marked effect on the heading of early cultivars such as Gremie and Aberystwyth S24, the behaviour of later cultivars is more directly affected by temperatures at the time of their stem internode elongation. Ear emergence dates of late cultivars bear no fixed relationship to those of early cultivars. It is concluded that while records of early spring temperatures can be used to predict, with reasonable accuracy, the heading dates of early cultivars, such records do not provide a reliable basis for the prediction of heading dates of later cultivars. In Northern Ireland, reliable prediction of cutting dates for later cultivars to obtain herbage of a required level of digestibility is only possible on a short-term (one-two week) basis. Such predictions must take account of growing conditions in each individual year.     

COMPARING THE OUTPUT FROM MIXTURES BASED ON PERENNIAL RYEGRASS AND ON MEADOW FESCUE

Herbage and livestock production from swards based on meadow fescue and on perennial ryegrass were measured over three years. The meadow fescue mixture had no practical advantages in terms of either annual output or seasonal distribution of production. This may have been due to inefficient methods of measurement or may have been peculiar to the management imposed, but it is considered that it was due to the depressing effects of timothy and cocksfoot on the meadow feseue.     

SEED PRODUCTION STUDIES ON PERENNIAL RYEGRASS, TIMOTHY AND PRAIRIE GRASS

A study over two years involving tiller identifica tion according to month of origin enabled the contribution of individual tillers of perennial rye grass Grasslands Ruanui, timothy Grasslands Kathu and a local New Zealand strain of prairie grass (Bromus unioloides) to be determined at seed harvest. In addition, the distribution of seed-heads in different arbitrary emergence groups was detemined so as to allow analysis of individual seedhead components within each group. In all species, tillers formed during the first 4 months following an autumn sowing in the first year, and also in the immediate post-harvest period and through the autumn in the second year, made a major contribution to seedhead numbers and seed yield at harvest. These tillers had a lower vegetative mortality rate than those formed in the spring. Primary tillers formed after sowing were highly persistent and became almost exclusively repro ductive. Many vegetative tillers died before har vest, behaving as annual tillers. Spring-formed tillers made a major contribution to the vegetative growth of the plant over the summer and early autumn. These tillers generally died before the following winter. Tillers formed in winter and early spring by ryegrass and prairie grass showed a high mortality, particularly in the second year. In timothy, mortality was highest amongst tillers formed in late spring. The reduced contribution of spring-formed tillers to the seed head population occurred as a result of fewer heads numerically compared with older tillers. In all species, most seedhead components varied according to time of ear emergence. Early emerged heads were generally longer, bore more spikelets and more florets per head and had a greater culm length than late-emerged heads. The major trend in all species was a general depression in head length, spikelet and floret number and culm length with grazing. These effects were in most cases partly or completely overcome by N application. The major effect of applied N was to increase floret number per head.     

SEED PRODUCTION STUDIES ON PERENNIAL RYEGRASS, TIMOTHY AND PRAIRIE GRASS

This paper considers the sequence of seed development by measurement and observation of ehanges in seed moisture content, weight, colour, endosperm consistency, germination capacity and yield in perennial ryegrass Grasslands Ruanui, timothy Grasslands Kahu and a New Zealand strain of prairie grass (Bromus unioloides). Seed moisture content was high (60–70%) after anthesis and declined at different rates, depending on the species and the weather. Maximum seed dry weight (maturity) was reached approximately 30 days after peak anthesis in all species and was influenced by N application and grazing. Colour changes in the seedhead and endosperm solidification proved unsatisfactory as measures of maturity. Endosperm solidification was reached 4, 11 and 12 days before maximum seed dry weight in ryegrass, timothy and prairie grass, respectively. Seeds removed from the plant as little as 7, 10 and 4 days after anthesis in ryegrass, timothy, and prairie grass, respectively, germinated, provided that dormancy was broken; but they did not retain viability after 3 months storage. Maximum viability of ryegrass, timothy and prairie grass seed tested immediately after harvest occurred 30, 38 and 16 days after anthesis, compared with 17, 35 and 12 days, respeetively, when germination testing was delayed for 3 months. In ryegrass, grazing caused a significant increase in seed yield in the second year while N application alone did not significantly increase yield. In timothy, grazing and to a lesser extent N, were both detrimental to seed yield in the second year. Highest yields were obtained in treatments not receiving either grazing or N. In prairie grass, grazing depressed and N application increased yields in both years. In all species similar or increased yield could be obtained by mowing the crop at, or slightly prior to, seed maturity and allowing seed development and ripening to continue on the cut straw for up to 10 days. Using this technique higher seed yields were obtained in ryegrass and timothy than when seed was direct-harvested. In prairie grass similar yields were obtained whether the erop was direct-harvested or threshed following drying in the swath for 10 days. The use of ‘drying curves’ for the prediction of correct cutting time of seed crops is suggested for ryegrass, timothy and prairie grass.     

THE EFFECT OF LEVEL OF NITROGEN FERTILIZER ON BEEF PRODUCTION FROM GRAZED PERENNIAL RYEGRASS/WHITE CLOVER PASTURES

In a 3 × 3 factorial experiment, the effects of three levels of nitrogenous fertilizer (0, 336 and 672 kg/N per ha) and three grazing intensities on live-weight gains and carcass attributes were measured.
The live-weight gains of the animals (per head) over the season were greater at the low and moderate grazing intensities than at the high; this effect occurred mainly from July to October each year. Gains were low on the no-nitrogen swards from July 1962 to the end of the grazing season and throughout 1963: this was related to the very high clover content of the swards.
In all years, as grazing intensities increased, the carcass weights per animal became lower. Carcass balance, carcass length, depth of longissimus dorsi muscle, fat thickness over the longissimus dorsi, weight of kidney suet and channel fat, and weight of the alimentary tract also reflected the effect of treatment on weight gains.
The results are discussed in relation to the botanical composition and consumption of the herbage, presented in Part I.     

COMPARATIVE STUDIES OF PERENNIAL RYEGRASS, TIMOTHY AND MEADOW FESCUE

The voluntary intake by calves of perennial ryegrass, timothy and meadow fescue, when cut with a flail-type forage harvester and fed fresh, was measured. In 1963 a single management was used and rest periods between cuttings were of 10 or 11 days in April and May and 21 days in June to October. In 1964 the effects of managements with long (35–55 days) and short (15–25 days) rest periods were compared. The increases in rest periods within managements were made in June or July. The voluntary intake of the 3 grass species was not significantly different and the live-weight gains made on the species were similar in both years. Digestibility of all species was higher with the short rest periods than with the long ones and this resulted in higher intakes and liveweight gains from the short-rest-period management.