Length of life of grass roots

The length of life of the root axes of a plant was taken as the interval between the prevention of the plant from producing any further axes and the death of the shoot. Of the cultivated species studied Lolium perenne had the shortest lived roots and Dactylis glomerata the longest with Phleum pratense, Festuca arundinacea, F. pratensis and F. rubra intermediate. Holcus lanatus and Nardus stricta had long lived roots comparable with Dactylis glomerata. The ranked order of species is in general agreement with the observations reported in the literature.     

Yield and stability of yield of single- and multi-clover grass-clover swards in two contrasting temperate environments

Diversity of clovers in grass-clover swards may contribute to greater herbage yields and stability of yield. This possible effect was evaluated in an experiment carried out over three harvest years at two contrasting sites, differing in precipitation and soil composition, using mixed swards containing either one, two or three clover species sown together with timothy ( Phleum pratense L.) and meadow fescue ( Festuca pratensis L.). The clover species were red clover ( Trifolium pratense L.), white clover ( Trifolium repens L.) and alsike clover ( Trifolium hybridum L.) sown in various proportions in a total of ten treatments. All swards were fertilized with nitrogen with amounts that increased from year to year, and three harvests were taken in three consecutive years. There was a significant interaction between site and species mixture on total dry matter (DM) yields (range 27–32 tonnes ha⁻¹) and DM yields of clovers (range 5–15 tonnes ha⁻¹); red clover as a single species or in a mixture was superior at the dry site while multi-clover species mixtures were superior at the wet site. Alsike clover was the least productive species of clover. Stability of yield of clovers was generally higher by including white and red clover in the seed mixture but total DM yield was not.     

Growth of white clover in eight grass species and the effects of propyzamide, a grass-suppressing herbicide

Seedlings of white clover (cv. Grasslands Huia) were introduced as spaced plants into 3-year-old monoculture plots of eight grass species ( Agrostis capillaris, Agrostis stolonifera, Dactylis glomerata, Festuca rubra, Holcus lanatus, Lolium perenne, Phleum pratense and Poa pratensis ) during June 1984. In mid-April 1985 plots were split for application of propyzamide at the following concentrations: 0, 0·2, 0·4, 0·6 kg a.i. ha^-1.
During 1984 differences between clover seedling growth in the different grass species became apparent within 2 weeks; growth was greatest in F. rubra, P. pratensis and H. lanatus and smallest in D. glomerata, L. perenne and P. pratense. During 1985, when more N fertilizer was given, H. lanatus and D. glomerata, were equally competitive and clover contributed only 16–18% of the total herbage yield of 10·4 t ha^-1 in them, compared with 33–50% of yields ranging from 9·6 to 119 t ha^-1 in the other six species. Propyzamide decreased grass growth in mid-season by more than 50% but there was little overall persistent benefit to clover yield, except for A. stolonifera and P. pratense with 0·4 and 0·6 kg ha_-1 treatments. Dactylis glomerata and perenne were least and H. lanatus, F. rubra and P. pratensis most suppressed by the herbicide.
Possible reasons for the overall large clover contribution from a very sparse seedling population and the relatively small effects of propyzamide are discussed as well as future work required to improve the predictability of effects of grass suppression.     

THE INDUCTIVE REQUIREMENTS FOR FLOWERING OF SOME TEMPERATE GRASSES

A survey was made of the flowering responses of 47 annual, biennial and perennial grasses, to measure the extent of any winter requirement for floral induction, and to see how far this could be provided by controlled cold or short-day treatment.
The annual species showed little or no inductive requirement, nor did the perennials Arrheuatherum elatius, Ceratochloa unioloides, Phleum pratense and Poa nemoralis . Most perennials possessed a definite inductive requircinent. A few species, such as Lolium perenne , responded to both cold and short-day given to the young seedling, while others, such as Phleum nodosum, Agrostis alba, A. canina, A. stolonifera and A. tenuis , responded to short-day induction but not to cold.
Many temperate perennials, however, including Cynosurus cn'status, Dactylis glomerata, Festuca pratensis, F. rubra, Poa pratensis and P. trivialis did not respond to seedling induction and possibly have a juvenile stage before they are able to respond to inductive conditions.
The sequence of flowering responses in the temperate perennial grasses is evidently more complex than was previously thought, and the perennial habit can be achieved by many different developmental pathways.     

The performance of high-latitude grass varieties under Scottish conditions: seasonal distribution of dry-matter production

The seasonal patterns of dry-matter (DM) production by swards of Norwegian grasses originating from high latitudes >61°N ( Dactylis glomerata Hattfjelldal, Phleum pratense Engmo and Poa pratensis Leikra) were compared over 2 years (1986 and 1987) with those of grasses developed at lower latitudes, 52°N ( Dactylis glomerata Cambria, Phleum pratense Motim and Lolium perenne Perma) at a lowland site in southwest Scotland (55.5°N, altitude 45 m). In each year, there was a significant enhancement of the DM production of the high-latitude varieties of Dactylis glomerata, Phleum pratense and Poa pratensis at harvests during May and June, although the lower latitude grasses gave a higher proportion of annual production than the Norwegian grasses in April and from September onwards. These findings are compatible with the observed stimulation of DM production of high-latitude grasses by daylength extension under controlled conditions. However, since the stimulation of DM production did not occur until the normal peak of production in May and June, it served to accentuate the skewed distribution of production in Scotland, rather than to improve production earlier in the season. Since the total annual DM production was significantly lower for the high-latitude grasses in general at the lowland site, there does not appear to be a clear role for these grasses in UK agriculture.     

Effects of cultivars of tall fescue (Festuca arundinacea Schreb.) on the botanical composition of mixed swards

The effect of five cultivars of Festuca arundinacea on the botanical composition of mixed swards (with Dactylis glomerata and Trifolium repens singly and combined) at two soil fertility levels (moderate fertilizer application and no application) were examined. Shoot and root morphological characteristics of seedlings in each cultivar were also examined under pot conditions.
Although there was little difference in the total biomass of the three mixed swards between cultivars, the cultivars showed significant differences in their relative contribution to total biomass. The relative order of competitive ability between cultivars was maintained over the different soil fertility levels and different species associations.
Of the two yield components of a grass sward, tiller number and tiller size, number of tillers showed a larger response to the presence of neighbour species than mean tiller size, and thus success of F. arundinacea cultivars in mixed swards depended on the extent of reduction of number of tillers caused by the neighbour species of mixtures. The least competitive cultivar had the smallest seeds and shortest roots.     

The susceptibility of agricultural grasses to pre-emergence damage caused by Fusarium culmorum and its control by fungicidal seed treatment

A total of 104 cultivars of six agricultural grass species were compared under controlled conditions for their relative susceptibility to the common soil-borne fungus Fusarium culmorum (W.G.Sm.) Sacc. A number of the perennial ryegrass ( Lolium perenne ) cultivars showed a high degree of resistance, their emergence being little reduced under the stringent test conditions. The emergence of others was, however, severely affected. Italian ryegrass ( L. multiflorum ) cultivars generally had a high level of resistance, the outstanding exception being cv. Leda Daehnfeldt which proved very sensitive. None of the cultivars of cocksfoot ( Dactylis glomerata ), timothy ( Phleum pratense ), meadow fescue ( Festuca pratensis ) or tall fescue ( F. arundinaceae ) which were tested had more than a moderate level of resistance and most were highly susceptible.
The vigour of ryegrass seedlings was, in most cases, closely correlated with percentage emergence but was less closely correlated in the more susceptible species. These often had a very low emergence but those seedlings which did establish were frequently of a size similar to that of healthy plants.
Treatment of grass seed with a fungicide mixture of benomyl (15% a.i.) plus captan (60% a.i.) provided excellent protection against F. culmorum on even the most susceptible cultivars.
Drazoxolon (40% a.i.) was, however, much less effective.     

A comparison of root competition and shoot competition between Dactylis glomerata and Holcus lanatus

Dactylis glomerata and Holcus lanatus were grown together in boxes with either full competition, root competition only, shoot competition only or no competition between them. The boxes were either fertilized (150 kg ha^-1N, 100 kg ha^-1 K, 80 kg ha^-1 P) or not fertilized. The experiment was continued for 13 months, and a total of six cuts were taken.
H. lanatus was more competitive than D. glomerata throughout the experiment, though the effect declined after flowering during the second growing season. The effects of root competition were generally much greater than those of shoot competition and tended to increase during the first year. However, the effects of root competition declined, relative to shoot competition, after flowering in the second growing season.
Fertilizer applications slightly increased the root competitive ability of H. lanatus relative to D. glomerata but slightly reduced its shoot competitive ability.     

Leaf dynamics of timothy and meadow fescue under Nordic conditions

Leaf production dynamics of timothy ( Phleum pratense L. cv. Tarmo) and meadow fescue ( Festuca pratensis Huds. cv. Kalevi) were studied in Finland under field conditions in mixed swards containing timothy, meadow fescue and red clover ( Trifolium pratense L. cv. Björn) harvested by cutting. Fifteen randomly selected tillers of both species were marked and leaf number, leaf appearance rate (LAR), leaf elongation rate (LER), leaf senescence rate (LSR) and leaf live span (LLS) were followed through weekly observations. Concurrently another set of fifteen tillers of each species was dissected on each occasion to determine the number of unemerged leaves and development stage of the apex. The first observation period was between 26 April and 22 June and the second between 22 July and 22 September.
The species differed clearly for most of the measured parameters but most differences were dependent on the season. In spring, timothy started growth earlier, had higher LAR (+57%), produced more leaves (+83%) with higher LER_gross (+58%), higher LSR (+61%), higher LER_net (+54%) and produced larger tillers (+193% in leaf area) than meadow fescue. In autumn, timothy still had a higher LAR (+80%), produced more leaves (+60%) with higher LER_gross (+36%), but had also a higher LSR (+77%) and thus similar LER_net (0%) to meadow fescue. Timothy tillers were only slightly larger than meadow fescue tillers (+20% in leaf area). The consequences of these findings on competition in mixed swards and implications for grazing theories are discussed.     

Leaf appearance and senescence patterns of some pasture species

Five pasture species, very different in their morphological organization (four dicotyledons: Plantago lanceolata, Sanguisorba minor, Ranunculus repens, Taraxacum officinalis and one grass: Dactylis glomerata ), were grown as spaced plants in pots, thus excluding competition for light, to study the proportion of senescent leaves. In May, after a 6 month period, the proportion of partially or totally senescent leaves varied from 20% to 80%. Four plant characteristics were important: leaf appearance and senescence rates, leaf lifespan and date and type of flowering. Plantago lanceolata had the longest lived foliage and the smallest proportion of senescent leaves. In contrast, Taraxacum officinalis had the most rapid leaf turnover and Dactylis glomerata had the slowest rate of leaf appearance. Sanguisorba minor and Ranunculus repens were almost identical, with intermediate leaf characteristics in all respects. These results illustrate the fact that the four characteristics studied, and not simply the species' phenology, must be taken into account in order to compare growth between species. The likelihood of these characteristics remaining the same when species are in dense sward is considered.     

Forage selectivity by cattle and sheep co‐grazing swards differing in plant species diversity

Interactions between sward diversity and forage selectivity of cattle and sheep managed within mixed grazing systems are not fully understood. The objective of this study was to investigate the effect of either mono‐ or co‐grazing of sheep and cattle on swards differing in botanical composition (either diverse or grass‐dominated) on the intake choices of six target forage species. Jacobs' selection index (JSI) was employed to quantify the preference for single target species in relation to their proportion in the sward. Results revealed distinct intake preferences of sheep and cattle; as expected, sheep were more selective than cattle. To a lesser extent, the sward composition had an effect on intake preferences: cattle responded to botanical composition by changing their intake preferences, but to a lesser extent than sheep. Phleum pratense was the most preferred target forage species (JSI = 0.62). Lolium perenne, Taraxacum sect. Ruderale and Trifolium repens were also highly preferred regardless of sward composition or type of grazing (JSI = 0.47, 0.32 and 0.27 respectively). Dactylis glomerata and Festuca pratensis tended to increase in abundance after grazing events in both diverse and grass‐dominated swards. Co‐grazing of cattle and sheep facilitated a more homogeneous consumption of the target forage species evaluated.     

Effects of soil compaction on root development of perennial grass leys in northern Norway

The effects of soil compaction on root development in leys were investigated at three locations in northern Norway: Sortland, Tromsø and the Pasvik Valley. At these sites, different soil amelioration measures and drainage methods of peat soils had been used. The investigations were carried out in 5-year-old Phleum pratense/Festuca pratensis or P. pratense/Poa pratensis leys. Tractor traffic decreased the maximum root depth at all sites, and the number of roots at 10-25 cm depth in the plough layer. The influence of compaction on root development in the upper 5 cm of the soils varied between the sites. A significant decrease was found for all compaction treatments at the Pasvik Valley, whereas only the heaviest compaction, with the use of double rear wheels, caused a significantly decreased number of roots in the upper 5 cm of the soil at Sortland. Soil compaction significantly decreased the infiltration rate at all sites. A significant positive correlation was found between infiltration rate and air-filled porosity.     

GRASSES IN WINTER

The Aberystwyth district experienced exceptionally cold winter weather in 1954, 1955 and 1956, especially during the period from the end of January to early March. Its effect on the grasses, both in the single-plant nurseries and in the agronomic experimental areas, is briefly described.
It was observed that plants which entered the winter carrying a bulk of herbage in a winter-proud condition were at a disadvantage compared with those which had been reasonably grazed or cut back during the autumn. The younger plants were found to be better able than the older ones to withstand extreme conditions.
Suggestions are made as to how some simple-mixture swards can be managed so as to be reasonably likely to provide keep in situ during the difficult months December to April. The species under consideration are cocksfoot ( Dactylis glomerata ), timothy ( Phleum pratense and P. nodosum ), tall fescue ( Festuca arundinacea ), perennial ryegrass ( Lolium perernne ) and Italian ryegrass ( L. italicum ).     

The introduction of red or white clover into a perennial grass sward

Sowing and post-sowing management techniques were assessed for their effectiveness in introducing Trifolium repens and T. pratense into an established Phalaris aquatica sward in spring and autumn.
Percentage emergence, seedling survival, seedling weight and final clover content were greater with T. pratense than with T. repens . Surface sowing gave 10% emergence compared to 62% for tilled treatments. Rotary sowing gave superior emergence in autumn, while tined sowing gave superior emergence in spring. However, seedling survival and weight, and therefore final clover content, were generally greater with rotary sowing than with tined sowing.
The removal of competition from the resident grass by bandspraying with glyphosate prior to sowing, and repeated lenient defoliation postsowing, increased final seedling numbers by 19% and 46%, respectively, and their individual weight by 29% and 82%, respectively.
The results showed that direct sowing in spring or autumn can be used to restore successfully a substantial population of clover plants to an existing perennial grass sward. They also demonstrated the importance of management to manipulate the environment of the developing clover plant.     

Copper and other minerals in herbage species and varieties on copper-deficient soils

The mineral composition of Lolium perenne, Dactylis glomerata, Trifolium repens, Lotus corniculatus and six non-leguminous broadleaved herbs was determined at two sites on copper-deficient soils with and without soil-applied copper sulphate at 2 kg Cu ha^-1. D. glomerata was richer than Lolium perenne in P, Mn and Cu, and T. repens was richer than either grass species in Ca, P, Mg and Cu. D. glomerata cultivars differed in Ca, P, Na and Mg concentrations, and L. perenne cultivars in Ca concentration. Lotus corniculatus contained less Ca, P, Na and Mn but more Zn than T. repens. Achillea millefolium was rich in K, Cichorium intybus in K, Mg and Zn, Petroselinum crispum in Na and Zn, Rumex acetosa in K, P, Mg and Zn and Taraxacum officinale in Na, Mg and Zn. Rumex was low in Na and Plantago lanceolata in Na and Mn. None of these herbs was richer than T. repens in Cu. Copper sulphate application raised the Cu concentration of the herbage only slightly, species or varieties differing little in their response to applied Cu. It is concluded that adjustment of botanical composition, with or without copper sulphate application, will not help to prevent hypocupraemia in grazing stock.     

Some effect fluid-sowing, pre-germination, irrigation and soil covering on the establishment and growth of seedlings of white clover slot-seeded into permanent pasture

Seeds of white clover ( Trifolium repens ) were sown alone or in fluid, or pre-germinated in fluid on to the soil surface of slots cut in an old Agrostis/Festuca sward. Seeds were left uncovered or covered with a thin layer of soil and irrigated from the outset or after 14 days delay.
With irrigation from the outset, seedlings established soonest from pre-germinated seeds but final percentage establishment ranged only from 50 to 63% for the three states of seed. With delayed Irrigation, however, few pre-germinated s1 survived and although germination of dry seed was delayed, final percentage establishment was unaffected. Soil covering increased establishment slightly. The number of leaves per seedling was greatest with pre-germination and early irrigation and least with pre-germination and delayed irrigation. Delayed irrigation also decreased the number of leaves per seedling for seedlings grown from dry seed.
The effects of early irrigation persisted so that at 84 days it significantly increased total yield of clover from all three states of seed, on average threefold, but much more from pre-germinated than from dry seed. Soil covering greatly increased yield, especially where irrigation had been applied from the outset. The interaction of early irrigation and soil covering was even more pronounced for stolon weights, and stolon growth of Individual seedlings appeared to benefit more from soil covering than from early irrigation.
The results showed the importance of early seedling emergence, but no advantages of fluid sowing per se. They also indicated large overall beneficial effects of early irrigation and its additive interaction with soil covering.     

Influence of long photoperiods on the growth of timothy (Phleum pratense L.) varieties from different latitudes in northern Europe

Plants of three varieties of Phleum pratense L. from different latitudes (cv. Engmo, 69°N; cv. S48, 52°N; cv. Motim, 52°N) were grown from the five-leaf stage at 12°C under continuous illumination or 8-h days at essentially identical daily inputs of radiant energy. The responses to daylength extension (increase in plant dry weight, plant height and leaf dimensions and reduction in the number of tillers per plant and in tissue dry matter content) were common to all three varieties and although the enhancement in plant dry weight and in leaf size was greater in the Engmo plants, this was principally the result of poorer growth and smaller leaf size in 8-h days. Marked differences between Engmo and the other varieties in the partitioning of dry matter within the plant were the consequence of differences in the rate of reproductive development. For example, compared with S48 and Motim, first spike emergence and 50% anthesis in the Engmo plants were delayed by 22 and 14 days, respectively, and 40% of the Engmo plants did not become reproductive even after 110 days of long-day treatment. Furthermore, by the time that 50% anthesis of the mainstem spike had been reached by the long-day plants of each variety, significant differences in tiller numbers and tiller fertility had developed between the varieties from high and lower latitudes. These findings and the results of previous studies of Poa pratensis, Dactylis glomerata and Bromus inermis are discussed in relation to the adaptation of high-latitude grasses to the Scandinavian environment.     

Effects of an established sward of Lolium perenne L. on the growth and development of Rumex obtusifolius L. seedlings

Seedlings of Rumex obtusifolius L. were grown in gaps (11 cm diameter) in an established sward at Lolium perenne L., Root competition from the surrounding sward was controlled by PVC tubes and shoot competition was controlled by cutting the sward frequently. All combinations, with and without root competition and with and without shoot competition, were used.
Plants received either 40 or 80 kg N ha⁻¹ month⁻¹ and 0 or 300 kg K₂O ha⁻¹ and were harvested 39 d after emergence; a second harvest was made 12 d later, after shading to 20% of full sunlight.
The shoot dry weight per plant of R. obtusifolius was much more affected by root competition than by shoot competition, especially at low nitrogen applications. Potassium supply had no effect.
More dry matter was allocated to the leaf petioles under shaded conditions and the specific leaf area was greater. This morphological plasticity enabled R. obtusifolius to grow well under shading and to be affected only slightly by shoot competition from L. perenne.
The results suggest that competition for nitrogen was the main factor limiting the initial grown of R. obtusifolius in a ryegrass sward and that the morphological characteristics of R. obtusifolius make it less susceptible to competition for light in the early stages of its development.     

Effect of nutrient application and herbicides on root competition between green panic seedlings and a Heteropogon grassland sward

Root competition was studied between seedlings of green panic ( Panicum maximum var. trichoglume ) and Heteropogon contortus in a native grassland sward clipped regularly to a height of 5·7 cm, and to which supplementary irrigation was applied. The influence of fertilizer addition and root competition from the grassland sward on seedling growth during the 42 days following emergence was determined. Root competition was excluded by steel tubes, or eliminated by killing the native sward with herbicides.
Seedling growth was poor where neither root competition was controlled nor fertilizer was applied; at 42 days the seedlings were still less than 6 cm high with three leaves and one tiller. When root competition was controlled, either by steel tubes or herbicide, seedling growth increased significantly. Growth was greatest in the herbicide-treated plots where fertilizer was applied, seedlings at day 42 being 48 cm high with sixty-three leaves and nineteen tillers.
Competition for nutrients appeared to be the primary factor limiting seedling growth and this was largely overcome by fertilizer application. Competition for nutrients appeared to increase the fertilizer requirements of pastures oversown into live swards compared with that of pastures oversown into herbicide-treated swards.     

Effect of season and cutting frequency on root and shoot competition between Festuca pratensis and Dactylis glomerata

Abstract Plant competition strongly affects the species composition of managed grassland. To identify relevant processes, Festuca pratensis (Huds.) and Dactylis glomerata (L.) were grown as monocultures or mixtures in boxes placed in the field for two seasons and subjected to two cutting frequencies. Root and shoot competition effects were separated using soil and aerial partitions. Shoot competition was analysed by measuring the vertical distribution of the leaf area and root competition by analysing the absorption of tracers. Values of relative yield indicated that the two grasses fully competed for the same limiting resources under the experimental conditions. The competitive ability of F. pratensis was lower during both years relative to D. glomerata. This was mainly related to its consistently lower shoot competitive ability, which was associated with less leaf area in the upper layers of the canopy and shorter leaves. Root competitive ability of F. pratensis changed with season. It was similar to that of D. glomerata during spring and autumn, but less during summer. The lower root competitive ability in summer might be due to the lower root activity of F. pratensis, measured as rubidium (Rb) and strontium (Sr) absorption in July, 0·1 and 0·2 m below the ground. Cutting frequency did not greatly influence the relative importance of root and shoot competition during the first growing season. However, under infrequent defoliation, the competitive ability of F. pratensis decreased markedly in full competition during the second growing season. These results suggest that distinct differences in the canopy structure and root activity of different plant species can affect the relative importance of root and shoot competition during the season.