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.     

Productivity of mixtures of Italian ryegrass and red clover

Two red clover ( Trifolium pratense ) cultivars, Red Head (tetraploid) and Kuhn (diploid), were sown at a seed rate of 13 kg ha⁻¹ either alone or in mixture with Italian ryegrass ( Lolium multiflorum ) cv. RvP sown at seed rates of 10, 15, 20 or 30 kg ha⁻¹. RvP was also sown alone at a seed rate of 30 kg ha⁻¹ and received nil or 300 kg ha⁻¹ fertilizer a⁻¹ fertilizer N. All plots were established using the barley cultivar Midas sown at a seed rate of 100 kg ha⁻¹ as a nurse crop.
Neither clover cultivar nor ryegrass seed rate significantly influenced either dry matter harvested or botanical composition over the 3 harvest years. On average over all years the grass-clover mixtures produced 75% of the yield of the N-fertilized RvP, 125% of the clover monocultures and 225% of the unfertilized RvP. The red clover contribution to the total dry matter harvested of the mixtures averaged 45–60%. The dry matter concentrations of the mixtures were considerably higher than those of the pure clover stands. In the third year yields were markedly reduced in comparison with those in the first and second years.
It was concluded that Italian ryegrass can be a suitable companion grass for red clover. Its superior yielding capacity over other grasses such as perennial ryegrass or timothy under a conservation management can be coupled to advantage with red clover to give a sward which Is essentially stable, at least over a 2- to 3-year cropping period, although giving slightly reduced yields in the third year. Italian ryegrass-red clover mixtures, without the use of fertilizer N, can produce high DM yields of good quality herbage.     

Lime and major nutrient fertilizers required to establish a perennial ryegrass/white clover pasture on a non-calcareous gley in the Scottish uplands

A field experiment with mixed swards of perennial ryegrass and while clover carded out in 1982–83 using small cut plots is described. With perennial ryegrass, lime slightly decreased annual dry matter (DM) production in 1982 (the sowing year) but increased it in 1983 (the first harvest year) by about 1 t ha^-1. Applications of N and P produced small increases in DM in 1982 and greater increases in 1983. In the latter season annual DM production varied from an average of 3·5 to about 10 t ha^-1 with 0 or 480 kg N ha^-1 applied in three equal-sized dressings throughout the growing season. Application of 40 kg P ha^-1 in 1982 increased DM production by about 2·5 t ha^-1 in 1983 but higher rates had little effect. Fifteen mg extractable P kg^-1 soil seemed sufficient to support levels of production normally expected from ryegrass pastures in upland Scotland, Applications of K did not affect DM production. N increased tiller weight and sward height of ryegrass; lime and P tended to increase tiller weight but this effect was not statistically significant. Leaf appearance and tiller number were not affected by treatments.
The white clover content of the pasture was decreased 10-fold by application of N and increased by lime and P (1·45 and 1·46-fold. respectively). The DM response to P was most apparent in limed soil and was also affected by the siting of the plots in the experimental area. Effects of lime and P on growth of white clover were to increase the number of stolon growing points and root nodule numbers per unit area.
The results emphasize the importance of lime and P fertilizer for establishment and growth of pasture in this soil and the differences between white clover and ryegrass in their responses to these.     

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.     

Seasonal variation in white clover content and nitrogen fixing (acetylene reducing) activity in a cut upland sward

The seasonal variation in herbage mass and nitrogen fixing (acetylene reducing) activity of white clover in an upland sward, cut weekly to 3·5 cm from mid-May until mid-October, was measured. Acetylene reducing activity (ARA) was measured over a 24-h period at 3-weekiy intervals starting on 3 March 1983. Clover leaf and Stalon biomass was measured by harvest of the assay truces, and from mid-May quadrat euts to 3·5 cm above the soil surface provided estimates of herbage accumulation.
Little A RA was detected in March, but activity increased substantially after 10 cm soil temperatures reached > 3°C, and peak activity per unit of clover leaf dry weight occurred in June and July; standing clover leaf dry matter increased during the season to a maximum of 60·5 g m⁻¹ in June. Acetylene reducing activity was positively correlated with the number of rooted nodes, and Stalon and leaf dry weights in early spring. Thereafter, except during a period of summer drought, ARA was positively correlated with the amount of clover leaf material.
Clover population density increased during the season and maximum growing point numbers (5540 m⁻¹) occurred in September; maximum leaf number per unit area (12 984 m⁻¹) was found in October, prior to the final cutting of the site.
Results suggest that higher levels of nitrogen fixation in upland swards should be obtained if sward management regimes, which encourage a high clover leaf area, are adopted.     

ABSORPTION OF RADIO–ACTIVE PHOSPHORUS FROM TAP–AND NODAL ROOTS OF WHITE CLOVER (TRIFOLIUM REPENS L.)

Absorption by the tap-root and by different nodal roots of white clover S100 and translocation of ³²P were investigated to find to what extent nodal roots can compensate for the absence of a tap-root. ³²P absorbed from the tap-root was distributed evenly within the whole plant. When translocation from the 2nd and 7th nodal roots was studied, similar distribution was obtained only from the nodal root closer to the centre of the plant. The backward movement of ³²P absorbed from nodal roots at the base of the plant increased as the root size increased. Removal of tap-roots resulted in temporary depression of translocation; its effect disappeared within 3 weeks.
It is concluded that the ability of nodal roots to compensate for loss of the tap-root depends on their position and size.     

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.     

Slot-seeding investigations

Red clover cv. Hungaropoly was slot-seeded into a perennial ryegrass-dominant sward in April 1979. Glyphosate and paraquat were applied separately as bandsprays each at two doses and at two band widths. Control plots were either slot-seeded without a herbicide bandspray or received ±150 kg N ha⁻¹ a⁻¹. Red clover establishment was assessed and amounts of dry matter (DM) and total N accumulated were measured at two harvests in 1979 and three harvests in 1980. Bandspraying increased seedling vigour and development and resulted in the eventual replacement of 1 t grass DM ha⁻¹ by an equivalent amount of red clover. Of the treatment variables investigated, bandspray width had the greatest influence on red clover establishment and productivity. The slot-seeded area, meaned for all treatments, produced a total of 6.40 and 13.16 t DM ha⁻¹ in 1979 and 1980. This was estimated to be equivalent to the all-grass sward receiving 112 kg N ha⁻¹ a⁻¹ during the second year of the experiment or 238 kg N ha⁻¹ over the 2 years when measured in terms of N yield. Slot-seeding overcomes several of the problems associated with conventional establishment of red clover.     

The future of sainfoin in British agriculture: an economic assessment

In view of the revived interest in sainfoin, an economic assessment of the prospects for an expansion of its area in Britain has been attempted. It is estimated that potentially it could be grown on 950 × 10³ ha of the agricultural area of England and Wales, though it is unlikely in the near future that it would exceed 20 × 10³ ha, even if economic conditions were favourable. Comparison of the energy and protein yields of sainfoin, red clover and lucerne under conservation management indicates that one of the attractions of sainfoin is its high protein content. However, an assessment of the costs of production and utilization of sainfoin indicate that, for it to be a more widely used legume, sustainable dry matter (DM) yields would need to be increased by 35% to about 11.5 × 10³ kg DM ha⁻¹. At the same time, although growing sainfoin as a mixture with grass appears to improve the economic attractiveness of the crop, silage production costs (kg DM)⁻¹ are still about 15% lower on pure grass swards. However, trials in the UK, Canada and Rumania have shown that, compared to current UK levels, sainfoin yields can be significantly increased.     

Effect of plant density and removal of ears on the quality and quantity of forage maize in a temperate climate

The present study was aimed at testing the hypothesis that a dense maize stand (320–720·20³ plants ha^-1) will produce more dry matter of acceptable quality than a stand sown at the density generally advocated (10⁵ plants ha^-1). It was also aimed at proving that grain is not essential in order to obtain a high yield of good-quality forage maize.
It was found that dry matter yield increased with density, especially at the early stages of growth. When ear-formation was depressed by increasing plant density, the resulting reduction of ear yield and its quality due to the absence of ear was partly compensated for by the increased yield and quality of the stem.     

Sward composition, animal performance and the potential production of grass/white clover swards continuously stocked with sheep

The potential productivity of perennial ryegrass/ white clover swards (GC) under continuous stocking management was assessed by comparing their performance, when grazed by sheep at sward surface heights of 3, 6 and 9 cm, with that of an all–grass sward (G) maintained at 6 cm and fertilized with 420 kg N ha^–1 The grass/clover swards received no nitrogen fertilizer. The different grazing treatments had a marked effect on animal performance. In the first year for example, for treatments GC3, GC6, GC9 and G6–420 respectively, mean stocking rates to weaning were 19–7, 14–3, 8–9 and 18–4 ewes ha^–1 (plus twin lambs); lamb growth rates were 223, 268, 295 and 260 g d^–1and so total lamb live weight gain was 1054, 920, 630 and 1148 kg h a^–1. The relative performance of the treatments was similar in all three years. All three grazing treatments had a similar effect on the composition of the grass/clover swards. Clover content increased in 1985, and was sustained in 1986 and 1987 during the main grazing season, although a marked decline in clover content during the winter led to a progressive long–term decline in both the proportion and the amount of clover.
It is suggested that a management based on maintaining a sward surface height close to 6 cm (as in all–grass swards) leads to optimum performance in grass/white clover swards grazed using continuous stocking with sheep. Despite the presence of a small and declining clover content, the output of the mixed grass/clover sward managed in this way was 80%, 80% and 82% of that of a grass sward supplied with 420 kg N ha^–1 in 1985, 1986, and 1987 respectively and, similarly, 83% of the output in 1987 of a grass sward receiving 210 kg N ha^–1.     

The liveweight gain of Limousin × Friesian heifers grazing perennial ryegrass/white clover swards of different clover content and the effects of their grazing on sward botanical composition

An experiment was carried out in 1992 and 1993 to examine the effect of white clover content of perennial ryegrass/white clover swards on the performance of Limousin × Friesian heifers. Swards with low (L), medium (M) and high (H) white clover contents were established and managed by continuous variable stocking. A compressed sward height of 5·5 cm was maintained using a buffer fence to vary plot areas, with herbage surplus to grazing requirements cut, removed and yields measured. The mean white clover proportions for treatments L, M and H were 0·02, 0·19 and 0·18 in 1992 and 0·13, 0·16 and 0·31 in 1993 respectively. White clover contents of the swards reached a maximum in August and September, and differences between treatments diminished. There was no significant difference between treatments in the content of white clover in the swards in autumn 1993.
Liveweight gains of heifers increased asymptotically with increasing white clover content of the sward. Below a white clover herbage mass of 300 kg DM ha^–1, there was little effect on liveweight gain, which was 0·70 kg day^–1 over the grazing season. Between 400 and 450 kg DM ha^–1 white clover, liveweight gains were 0·85–0·90 kg day^–1. While clover content of the sward did not significantly affect utilized metabolizable energy output; the mean output over the grazing season in the two years from liveweight gain and herbage yield was 78 GJ ha^–1. It is suggested that, using this grazing system, white clover reached an equilibrium with a mean herbage mass of about 400 kg DM ha^–1 over the grazing season.     

Seasonal changes in the crude protein concentration of mixed swards of white clover/perennial ryegrass grown without fertilizer N in an organic farming system in the United Kingdom

Changes in the crude protein (CP) concentration of white clover and perennial ryegrass herbage from a mixed sward were determined on six sampling dates from May to October in each of 2 years. The swards were grown without fertilizer N in an organic farming system and continuously grazed by dairy cows during the grazing season. The annual mean contents of white clover in the dry matter (DM) of the sward were 272·3 and 307·0 g kg⁻¹ in Years 1 and 2. The mean CP concentrations of the white clover and perennial ryegrass herbage were 251·6 and 151·9 g kg⁻¹ DM in Year 1 and 271·9 and 174·0 g kg⁻¹ DM in Year 2 respectively. The CP concentration of the white clover increased significantly during the grazing season from 220·0 to 284·1 g kg⁻¹ DM in Year 1 and from 269·0 to 315·5 g kg⁻¹ DM in Year 2. In the perennial ryegrass herbage the CP concentration increased from 112·2 to 172·6 g kg⁻¹ DM in Year 1 and from 142·7 to 239·5 g kg⁻¹ DM in Year 2. The rate of increase during the season in the CP concentration of the perennial ryegrass herbage was similar to the rate of increase recorded in the white clover herbage.     

An evaluation of the drop-disc technique for measurements of herbage production in ryegrass for silage

The drop-disc method of estimating herbage dry-matter production was evaluated for ryegrass from growth commencement to the silage stage; the latter typically corresponded to a maximum dry matter (DM) mass of almost 7 t ha⁻¹. A close linear relationship ( r ²= 0·829) was found between disc settlement height and DM mass up to 4–5 t ha⁻¹ for the period when growth was mainly vegetative rather than reproductive. During the latter stage, the presence of stems and the occurrence of lodging had a detrimental effect on the quality of disc calibration data. The technique was demonstrably useful in experiments as a cheap, rapid and trouble-free method for monitoring the initiation of grass production and rate of production during the vegetative stage.     

The effect of companion perennial ryegrass cultivars on red clover productivity when timing of the first cut is varied

Replicated plots of Hungaropoly red clover were sown on a sterilized area in May 1975 alone (seed rate 11 kg ha^-1) or with one of six cultivars of perennial ryegrass (seed rate 3·5 kg ha^-1) viz. Cropper and S24 (early heading), Barlenna and Hora (medium heading) and Melle and Perma (late heading). In 1976 and 1977 primary growth was cut at one of four dates ranging from mid-May to mid-June and thereafter plots were harvested twice each year.
Varying the time of first cut did not have a significant effect on total dry matter (DM) yield in either year despite differences in means of cutting treatments on annual red clover yields of the order of 6–9%.
In some companion grass treatments total DM yield in 1976 was increased and total red clover yield and percentage red clover contribution were reduced relative to swards sown only with red clover. In 1977 a similar but non-significant trend was found. Swards containing early ryegrasses had higher total herbage DM yields but lower red clover yields and contents than all other swards at the first harvest in both years.
Delay in date of taking the first harvest in 1976 reduced DM digestibility in the first cut and increased it in the second in both years.
It is suggested that by cutting early and increasing the number of harvests from three to four per year, differences in the content of red clover between the first and second cut might be reduced, and it is concluded that more benefit is derived from red clover when medium or late heading ryegrasses are used as companion grasses.     

The productivity of four forage legumes sown alone and with each of five companion grasses

Four legumes—white clover cv. Blanca, red clover cvs Violetta (diploid) and Hungaropoly (tetraploid) and lucerne cv. Europe—were established as pure-sown swards and with each of five companion grasses: timothy cv. Timo, meadow fescue cv. Bundy, sweet brome cv. Deborah and perennial ryegrass cvs Talbot (diploid) and Barlatra (tetraploid), both ryegrasses being of 'intermediate' heading date. Two 'silage' crops and an 'aftermath grazing' crop were harvested in each of three successive years.
In the first harvest year, total herbage DM production of red clover ranged from 15·03 to 17·01 t ha^-1. White clover and lucerne swards produced considerably less at 7·12 to 11·01 t ha^-1. In the second harvest year, lucerne swards were the highest producing at 15·54 to 17·14 t ha^-1, while DM production from red clover and white clover swards ranged from 6·75 to 11·87 t ha^-1. Lucerne swards maintained their production superiority in the third year at 16·48 to 17·87 t ha^-1, while production from white clover swards ranged from 6·41 to 10·23 t ha^-1. However, red clover swards declined to 3·30 to 5·81 t ha ^-1; this above-average decline was mainly caused by the onset of red clover necrotic mosaic virus which affected all red clover plots uniformly in the second harvest year, and by winter conditions before the third harvest year. Total herbage DOM and CP yields of the swards were influenced in a similar manner to DM production.     

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

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

Factors affecting the stolon growth of white clover in ryegrass/clover patches

The effects of spatial location of white clover ( Trifolium repens L.) within a perennial ryegrass ( Lolium perenne L.)/white clover pasture on stolon and petiole extension were investigated in two experiments, where patch size containing white clover (0·5 m, 1·5 m and 4 m diameter), location within the patch (inside and edge) and cutting height (4 cm and 8 cm) were varied. Stolon extension rate was greater on the edge of a patch (12·1 mm week⁻¹) than inside the patch (7·2 mm week⁻¹). Patch size affected both stolon and petiole extension rate, which were both greater in small and medium-sized than in large patches. It is suggested that the fastest spread of white clover in patchy sward environments should occur from small patches, which could double in diameter during a growing season. Manipulating the heights of vegetation within and outside large patches affected light quality (red-far red; R/FR) at ground level, which was greater under shorter than taller swards and greater under the canopy of the grass matrix than the grass/white clover patch. However, the height differences between adjacent vegetation had little effect on stolon or petiole growth. In May only, stolon extension at the patch boundary was greatest when both patches and the grass matrix had a height of 8 cm.     

Yield and composition of red clover treated with growth regulators in early spring

The effect of growth regulators on the yield and quality of red clover ( Trifolium pratense L.) was assessed in two growing seasons. An early-flowering cultivar (Florex) and a late-flowering one (Altaswede) were treated with the growth regulator, daminozide butanedioic acid [mono (2,2-dimethylhydnizide)] or mefluidide [ N -(2,4-dimethyl-5{[(trifluoromethyl)sulphonyl]amino}phenyl) acetamide], either in early (mid-May) or late (late May) season and at low rate [daminozide, 4kg active ingredient (a.i.) ha⁻¹; or mefluidide, 0·13 kg a.i. ha⁻¹] or twice the low rate (high rate), and compared with no treatment. Red clover yielded two- to three-fold more dry mater (DM) in the first than in the second harvest, and growth regulator treatments did not redistribute yields more evenly between the two harvests. Growth regulator effects on the yield and composition of red clover were mainly confined to the first cut herbage. Daminozide increased first-cut and annual yields of DM and in vitro digestible DM (TVD); the latter was increased particularly for Altaswede, as compared with the untreated red clover. Mefluidide decreased first-cut yields of DM and IVD for Florex only, but the annual yields for both cultivars were unchanged by this treatment. Changing the rate or time of growth regulator application did not affect DM or IVD yield in red clover. The treated red clover contained less water-soluble carbohydrate in the first cut than did the untreated crop. The high rate of daminozide, when applied early, decreased neutral detergent fibre and increased IVD contents in the first-cut red clover compared with the other combinations of rate and time. Altaswede produced as much DM annually and had a higher IVD content than Florex when these cultivars were cut on common dates, twice during the short growing season in Atlantic Canada.     

RED CLOVER SEED STORAGE FOR 23 YEARS

The moisture content of red clover seed proved to be the most important single factor governing its longevity. Life was conserved considerably better in a heated room, on account of its lower relative humidity, than in an unheated granary.
Low temperature (32°–41°F.) was shown to be very beneficial for maintaining viability when the moisture content was excessive (10.32 per cent). By replacing the air in the containers with dry CO₂ longevity was increased.
A combination of low moisture content, cold storage and replacement of air by dry CO₂ enabled red clover seed to germinate 71 per cent after 23 years' storage and produce vigorous seedlings.
Purple and yellow colours may be retained in a considerable proportion of a red clover seed stock long after all the seeds are dead.