The effect of variety and fertilizer nitrogen level on red clover production

Established swards of two diploid and two tetraploid red clover varieties sown pure received 0, 75, 150, 225 or 300 kg ha^?1 N fertilizer and were cut three times in June, August and October 1971. The total yields of herbage DM for red clover varieties ranged from 8.01 to 11.32 t ha^?1; swards sown with tetraploids Hungaropoly and Hera Pajbjerg were superior by 25% in DM yield and 23% in CP yield. The red clover contribution to these total yields of DM ranged from 6.05 to 10.69 t ha^?1; tetraploid clovers outyielded diploids by 42% in DM yield and 39% in CP yield. The mean effect of N level on yield and on compositional attributes was slight. Total yields of herbage DM, averaged over all varieties, ranged from 9.50 to 10.22 t ha^?1 and of total herbage CP from 1.76 to 1.91 t ha^?1. The influence of N level on the red clover contribution was negligible. DM yields ranged from 8.54 to 8.72 t ha^?1 and CP yields from 1.60 to 1.64 t ha^?1. Superiority of tetraploid clovers over diploids was again confirmed. Red clover swards sown pure can give high yields without the application of fertilizer N.     

Spring defoliation of white clover seed crops. 1. Inflorescence production of contrasting white clover cultivars

Three white clover cultivars, S184 (small-leaved), Menna (medium-leaved) and Olwen (large-leaved), were sown at a seed rate of 3 kg ha^-1 under spring wheat cv. Tonic. In the spring of the two following years, there were three pre-bud emergence mechanical defoliation treatments on which were superimposed four post-bud emergence treatments giving a total of twelve cutting treatments. Pre-bud emergence, plots were either cut twice (at approximately two weeks before bud emergence and at bud emergence), cut once at bud emergence or not cut. To each treatment were applied four post-bud emergence treatments: plots were not cut or cut once (one, two or three weeks after bud emergence). Counts of the total number of inflorescences and of the proportions in various ripeness categories were made throughout the period of seed crop development to determine the pattern of inflorescence development and optimum harvest date. Overall, inflorescence numbers were greatest in cv. S184and least in cv. Olwen. Defoliation before bud emergence had no effect on inflorescence production; however, it was significantly influenced by defoliation after bud emergence. Although delaying the initial development of the crop, inflorescence numbers of all cultivars were highest in both years following cuts two and three weeks after bud emergence. Optimum harvest date was not affected by defoliation or cultivar, numbers of ripe inflorescences in both years reaching a peak at the end of August. The number of brown inflorescences, which may also contribute to seed yield, reached a peak in both years in late July. Seasonal differences in inflorescence production were again observed, emphasizing the difference between first and second year crops and importance of climate in while clover seed production. The implications of these differences in numbers and proportions of inflorescences in various ripeness categories under different defoliation regimes are discussed in relation to seed crop management in the UK.     

The influence of date of sowing and seed rate on the production of pure-sown red clover

Hungaropoly tetraploid broad red clover was sown at seed rates of 6, 12 or 18 kg ha^-1 on six dates from April to September 1971. Three crops were harvested in 1972 and one in June 1973. In 1972, total herbage dry matter yields ranged from 5.22 to 12.22 t ha^-1 and red clover dry matter yields from 3.61 to 11.92 t ha^-1 when meaned over all seed rates. April to July sowing dates gave significantly higher yields than later sowings. In general, August and September sowings gave the lowest red clover contents in a range from 63.2 to 96.5%, the highest digestibilities within a range 61.9 to 65.0% and the lowest crude protein contents in a range 15.5 to 17.3%. The influence of seed rate was less marked than sowing date. Mean annual yields of total herbage dry matter increased from 9.88 to 10.85 t ha^?1 as seed rate was increased from 6 to 18 kg ha^?1. Red clover dry matter yields and contents of red clover and crude protein in the total herbage also followed this trend. The sowing date effects on total herbage yield and content of red clover did not persist into the second harvest year but the seed rate effects were still noticeable. Plant numbers in spring the first harvest year and hence percentage survival from sowing were depressed by late sowing; plant numbers rose but percentage survival declined as seed rate was increased. The seed rate effects on plant population persisted until spring of the second harvest year but sowing date effects did not. Better stands of red clover were obtained from sowings made between April and June, when a seed rate of 12 kg ha^?1 was adequate. The adverse effects of late sowing cannot be fully compensated by raising seed rates of clover. There was a significant interaction between seed rate and date of sowing. For April-May sowings, seed rate was not critical. Thereafter, a linear effect of seed rate on yield was discernible.     

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.     

Effect of seed rate of red clover and of companion timothy or tall fescue on herbage production

Tetraploid red clover (cv. Hungaropoly) was sown at seed rates of 6,12 or 18 kg ha^?1 alone and in mixture with timothy (cv. Scots) at 2, 4 or 6 kg ha^?1 or with tall fescue (cv. S170) at 6,12 or 18 kg ha^?1. Two ‘silage’ crops and an ‘aftermath grazing’ crop were harvested in 2 successive years. In harvest years 1 and 2, total herbage production levels of 11.12 and 7.47 t dry matter (DM) ha^?1 respectively were obtained from pure-sown red clover compared with 11.84 and 8.78 t DM ha^?1 for red clover-timothy and 12.23 and 9.64 t DM ha^?1 for red clover-tall fescue. Corresponding red clover production levels were 10.93 and 5.30 t DM ha^?1 (red clover swards), 8.04 and 3.131 ha^?1 (red clover-timothy), and 6.42 and 109 t ha^?1 (red clover-tall fescue). Total herbage organic matter digestibility was improved by the timothy companion grass but not consistently by the tall fescue, whereas crude protein (CP) concentration was decreased by the addition of either grass. Increased seed rate intensified these effects, as well as the general effect of the companion grass in depressing red clover DM, digestible organic matter (DOM) and CP production. Total herbage DM, DOM and CP were not markedly affected by increasing red clover seed rate but red clover DM, DOM and CP were increased as red clover seed rate was raised, due to increases in the red clover component. The potential for silage cropping of red clover swards was confirmed but there was advantage in sowing a companion grass. Taking yield and quality parameters into consideration, timothy proved a better companion than tall fescue. A seed rate of 2 or 4 kg ha^?1 timothy and 12 kg ha^?1 red clover proved the most satisfactory.     

Spring defoliation of white clover seed crops. 2. Potential harvestable seed yield and seed yield components of contrasting white clover cultivars

The effects of different spring defoliation managements on potential harvestable seed yield and seed yield components of three contrasting white clover cultivars were assessed. The small-leaved cv. S184 produced more but smaller inflorescences than the large-leaved cv. Olwen and Menna, a medium-leaved cultivar. Cultivar Olwen, however, produced more ripe and brown (nearly ripe) inflorescences with more florets, seeds per floret and a higher seed yield per ten inflorescences than the other cultivars. Potential harvestable seed yield and individual seed yield components were only influenced by defoliation after bud emergence, as defoliation before bud emergence had no effect on seed yield components. Defoliation after bud emergence had a similar effect on all cultivars: the number of ripe inflorescences was unaffected by defoliation but the number of brown and therefore harvestable (ripe + brown) inflorescences was highest following defoliation three weeks after bud emergence. Florets per inflorescence, seed per floret, 1000 seed weight, seed yield per ten inflorescences and potential harvestable seed yield were not influenced by defoliation after bud emergence. Season had a significant effect on seed yield components and influenced the effect of defoliation treatments, emphasizing the importance of climate in white clover seed production. The results are discussed in relation to the spring defoliation of white clover seed crops, harvesting techniques and the provision of guidelines for optimizing seed yield.     

The effect of drying techniques on formononetin concentration in red clover

Oven-drying at 60°, 80° or 105°C was compared with microwave and freeze-drying as a method of preparing samples for the estimation of formononetin, the major oestrogenic factor in red clover. There was no significant difference in the formononetin concentration of clover samples either oven-dried at 60°C or freeze-dried. The formononetin concentration was reduced by drying at higher temperatures and by microwave-drying but was not affected by wilting for up to 8 h after harvesting. The routine determination of formononetin in ten varieties of red clover showed no significant differences between samples cold stored at – 18°C prior to oven-drying at 60°C and samples freeze-dried.     

White clover seed production from mixed swards: effect of sheep grazing on stolon density and on seed yield components of two contrasting white clover varieties

A trial was carried out over two harvest years to assess the effect of sheep grazing and closing date on stolon density and seed yield components of two contrasting white clover varieties and to determine the potential for producing clover seed from mixed swards in an integrated livestock/seed production system.
Overall, the small-leaved cv. S184 had a higher stolon density at closing and harvest than the large-leaved cv. Olwen, but only significantly so in 1987. Stolon density at closing was generally increased by delaying closing. Varieties also differed in their response to closing date. Stolon density of cv. S184 in both harvest years, generally increased with later closing whilst cv. Olwen was less influenced by closing date and at all dates in 1987, and all but one date in 1986 was not significantly different from the ungrazed treatment.
Delay of closing significantly increased stolon density at harvest on all closing dates in 1987 but had no effect in 1986. Varieties responded similarly to a delay in closing but the magnitude of increase of cv. Olwen was less than that of cv. S184.
The seed yield components of both cv. S184 and cv. Olwen were influenced by closing date, but the effect differed between years. Although there was some initial increase in inflorescence production, delaying closing after inflorescence buds appeared on the stolon reduced inflorescence number of cv. Olwen in both years but reduced inflorescence number in cv. S184 in 1986 only. However, inflorescence size, seed yield per inflorescence and the proportion of ripe inflorescences at harvest was reduced in both years. Cultivar S184 produced more inflorescences than cv. Olwen in both years and in both years tolerated later closing than cv. Olwen.
The effect of sheep grazing and closing date is discussed in relation to stolon removal and the suitability of particular leaf types for this system of seed production.     

采收时间对油葵种子质量及品质的影响

为明确不同采收期对油葵种子质量和品质的影响,本研究以67×早R、36×早R和早熟矮大头3个油葵材料为研究对象,于开花后30、35、42、47 d收获种子,对相同条件下晾干的种子进行活力相关指标和品质指标测定.结果表明,67×早R和早熟矮大头在开花后42 d收获的种子,活力较高;36×早R以开花后47 d收获的种子,活力...     

The effect of time of sowing and sowing method on production of white clover in mixed swards

Two field trials were carried out in successive years in which (1) perennial ryegrass and white clover seeds were drilled together, or (2) clover was broadcast and grass drilled, or (3) both clover and grass were broadcast. The last two treatments were followed by harrowing or not of the seed bed. Sowing took place in early May or August. Four harvests were taken in each full harvest year. In establishment years, sowing in May resulted in a total dry matter (DM) production at least ten times higher than that resulting from sowing in August. No sowing method treatment effects on total DM or clover yield were significant in the establishment year (measured only in spring-sown plots). In the first harvest year the August-sown treatments produced 15% less DM than those sown in May and clover yield was, on average, 40% lower than the earlier sown treatments; clover proportion followed a similar pattern to yield. Drilling of both grass and clover without harrowing produced swards with a significantly lower proportion of clover in the first harvest year in the first trial than in treatments in which clover was broadcast but not harrowed. In the second trial at harvest 1, clover proportion just failed to be significantly lower in the treatment in which grass and clover were drilled than in the treatment when clover was broadcast and the seed bed harrowed. In the second harvest year (first trial only), annual clover yield and proportion were not affected but drilled grass and clover had lower DM yield than when grass was drilled and clover broadcast without harrowing and when both were broadcast, without harrowing. At one harvest, the yield of clover in treatments sown in May was actually lower than that in the later-sown plots. In a subsidiary controlled environment experiment to investigate the effect of stage of clover development on cold hardiness (a factor in autumn-sown swards), plants which were about to initiate stolons (58 days old) had an LD₅₀ of ?5·1° compared with ?9·3°C for plants 60 days older. It is concluded that autumn sowing delays the time at which optimum clover production is achieved (late in the first full harvest year) and method of sowing does not compensate for this. However, sowing in August under Northern Ireland conditions does not seem to jeopardize the chances of a successful establishment of white clover, and plants should be sufficiently winter hardy to withstand relatively hard freezing conditions.     

The effect of short-term grazing of red clover on ewes at mating

Four groups of ewes grazed swards of red clover (Trifolium pratense cv. Hungaropoly) for 28-day periods ending 28, 14 or 0 (two groups) days before mating. One of the groups on red clover for the period immediately before mating continued on red clover during mating. At all other times before mating and for 7–8 weeks after mating commenced these ewes were grazed on a predominantly perennial ryegrass-white clover sward. A fifth (control) group was on the ryegrass sward throughout. There was no apparent adverse effect of red clover on ovulation rate, conception rate or embryo mortality.     

The effect of row spacing and cover-crop on stolon development and the seed yield components of white clover cultivars of contrasting leaf size

Three white clover cultivars, S184 (small-leaved), Menna (medium-leaved) and Olwen (large-leaved), were broadcast or sown in 15, 30 or 60 cm drills at a seed rate of 3 kg ha^-1. The three cultivars were either sown without a cover-crop or sown under a cover-crop of spring barley (cv. Crescent) or peas (cv. Countess). The effects of these methods of establishment on the stolon growth and components of seed yield were subsequently measured.
Stolon growth and development was influenced by row spacing, cultivar and season. The overall plant response at all but the widest row spacing (60 cm) was to increase stolon growth such that inflorescence production, the number and proportion of ripe inflorescences and the other seed yield components were unaffected by row spacing. Cultivars differed in their response to row spacing. Cultivar Olwen produced most inflorescences and more ripe inflorescences when broadcast, cv. S184 when sown at 60 cm row spacing and cv. Menna at 15 or 30 cm row spacing. Cultivars also differed in their response to cover-crop, with cvs Menna and S184 producing more inflorescences and more ripe inflorescences when sown under barley and peas than when pure sown. The inflorescence production of cv. Olwen was not influenced by cover-crop.
The relationship between vegetative and reproductive growth is discussed in relation to establishment, cultivar and climate and the possible implications for the establishment of white clover seed crops in the UK.     

Competitive effects between ten cultivars of perennial ryegrass and three cultivars of white clover grown in association

In an experiment of four years duration, the competitive relationships between three cultivars of white clover ( Trifolium repens L.) and ten cultivars of perennial ryegrass ( Lolium perenne L.) were studied under a N fertilizer regime of 200–240 kg ha^-1 a^-1. The clover cultivars were selected to embrace the various leaf sizes from medium large to small and the ryegrasses included early, mid-season and late cultivars with a known range of persistence.
During the experiment there was a progressive decline in the contribution of clover, though the different characteristics of each of the clover and ryegrass cultivars produced substantial deviations from the average trend. The clover cultivar Kersey was significantly more aggressive towards the companion grass cultivars than either S100 or S184. It produced consistently greater clover contribution to total yield than the other two cultivars and significantly depressed the yields of some of the companion grass cultivars. There was evidence that compatibility of the ryegrass cultivars with clover was inversely related to persistence; the non-persistent ryegrass cultivars S321 and Presto consistently produced lower grass yields than the more persistent cultivars and consequently permitted greater clover contribution. In the second and third years yield substitution effects between clover and grass components substantially reduced differences in the total grass-clover yield.
The interactions revealed in the experiment showed that both ryegrass and clover cultivars have the potential to influence each other when in association although, with minor exceptions, total annual yields were similar for all grass and clover mixtures at the moderately high level of N applied.     

Factors reducing yield of organic white clover seed production in Denmark

Factors reducing yield of organic white clover seed production were investigated in Denmark. In thirty‐six fields from different regions, density of flower heads, and weevils of the genera Apion and Hypera, hatching from flower heads, were assessed. In fifteen of these fields, additional measurements were made in order to calculate potential yield and yield‐reducing factors. Flower heads had a mean of ninety‐two florets per head, of which proportionately 0·59 were intact, 0·08 were not pollinated and 0·34 damaged by weevils; 0·16 of the florets contained larvae of Apion species. In intact florets the mean number of seeds was 3·6. Density and size of flower heads were correlated with low density of flower heads leading to significantly more florets per head. The number of seeds per intact floret was correlated with the proportion of unpollinated florets. The number of insect‐damaged florets was influenced by both larvae of Apion in and the numbers of Hypera nigrirostris (Fabr.) hatched from flower heads. One larva of H. nigrirostris caused approximately ten times the damage of a larva of Apion. Densities of Apion and Hypera were influenced by location, with fields with adjacent weevil sources being most at risk. An estimate of potential seed yield showed that, even under good harvest conditions, only a small part of potential seed yield is realized and that under suboptimal harvest conditions seed loss is high. The main factors responsible for low yields in Danish organic white clover seed production were identified as unfavourable harvest conditions and weevil damage.     

Cattle slurry as a source of nutrients for red clover: herbage production and clover contribution

An established sward of red clover cv. Hungaropoly sown pure received approx. 30 kg P ha^-1 and 200 kg K ha^-1 each year for 3 successive years. The P and K were applied either as cattle slurry, inorganic fertilizer or combinations of these. Treatments were applied either in spring or after the first harvest. There were a total of six treatments and these were harvested three times each year. The average yields of total herbage DM over all the treatments in the first, second and third years were 15·2, 14·2 and 14·2 t ha^-1 respectively and the various treatments had no significant effect on the overall yields.
Treatments had a significnt effect on red clover DM yields and percentage red clover in one harvest in each of the first 2 years and all three in the third year. Yields of red clover were lower and grass higher in treatments receiving cattle slurry only. On this treatment there was a total yield of 23·2 t ha^-1 red clover DM in the 3 years compared with 30·2 t ha^-1 on the inorganic fertilizer treatments. However, by applying P and K fertilizer in the spring, followed by cattle slurry after the first harvest, it was possible to maintain a high proportion of red clover in the sward and to produce yields of red clover DM similar to those on the inorganic fertilizer treatments.     

A two-year comparison on nutritive value and yield of eight lucerne cultivars and one red clover cultivar

Red clover (Trifolium pratense) and lucerne (Medicago sativa) are among the most common legume species used for ruminant feeding systems. Besides the greater nutritive quality and first-year ley yield compared to lucerne, red clover decreases its yield over the years. However, under unfavourable soil conditions the persistency of lucerne can be compromised, not performing as expected. This study compared yield and chemical composition of eight lucerne cultivars and one tetraploid red clover cultivar, with similar growth capacity as lucerne, replicated over two years. In the second year, four lucerne cultivars and the red clover cultivar were analysed for crude protein (CP) fractions, dry matter and neutral detergent fibre (NDF) digestibility. A randomized block design was used with three field blocks per cultivar for the multiple comparisons within each year. There were differences in DM yield, concentrations of CP and NDF and CP fractions among the lucerne cultivars, but the differences were inconsistent between years and between growth cycles within year. The red clover cultivar had lower CP and NDF concentrations than a majority of the lucerne cultivars, and greater in vitro organic matter digestibility compared to all of the lucerne cultivars. Also, the red clover cultivar had greater rumen undegradable-to-degradable CP ratio but confirmed its lower yield persistency compared to the lucerne cultivars.     

The effect of different cultivars of clover on numbers of and leaf damage by, some invertebrate species

Invertebrate numbers were studied in two white clover cultivars trials, grown with perennial ryegrass Weevils ( Sitona spp.), slugs, lucerne flea, leatherjackets and as were more common (at least at some life stage) in cultivars of lower cyanogenic potential. Damage to clover foliage by the first three species was also negatively related to cyanogenesis. The production of HCN ranged from 0.025 mg to about 1.8 mg g⁻¹ fresh leaf. There was no evidence of any other factor influencing cultivar preference.
Cyanogenesis had most effect on numbers of weevil larvae and leatherjackets. The effect on weevil larvae was attributed partly to intercultivar differences in oviposition, but it was also suspected that larvae had fed on cyanogenic parts of the plant before reaching the root. Leatherjacket numbers developed inter-cultivar differences during larval growth. In one case these differences were detectable by December. By March in the second experiment there were approximately three times as many leatherjackets at the low as at the high end of the cyanogenic range. Approximately four times as many Sitona larvae were found at the lower as at the higher end of the scale. There was some evidence that a higher clover content in the sward was attractive to ovipositing Tipula paludosa but not in recently harvested cultivars of high cyanogenic potential     

The fertility of heifers consuming red clover silage

The fertility of forty-two heifers offered either red clover silage or grass silage prior to and during the period of insemination was compared. Pregnancy rate to first service was significantly higher ( P < 0·25) on red clover silage at 76% compared with 43% on grass silage. Pregnancy rates from a mating period covering three oestrus cycles were similar on the two silage diets. The ratio of services to pregnancies was lower on red clover silage (1·2) than on grass silage (2·2). In a subsidiary trial with twenty-three heifers, pregnancy rate to first service on red clover silage was 78%.
There was no evidence to indicate that herd fertility is depressed by red clover silage.     

Thermal time approach to predicting seedling emergence dates of red clover,white clover and lucerne in farm fields

A practical method for predicting seedling emergence dates of red and white clovers, and lucerne is proposed. The germination response at seven different constant temperatures ranging from 5 to 35°C was examined. Germination rate, which is a reciprocal of the duration for 50% germination of seeds, was linearly regressed against temperature to calculate the base temperature and thermal constant of seed germination. The calculated values were 3·9°C and 15·8 degree days for red clover, 4·2°C and 13·6 degree days for white clover, and 2·9°C and 17·7 degree days for lucerne. Using the base temperatures, thermal constants, and the daily mean air temperatures at the study site, the seedling emergence dates of the three forage legumes were predicted. At the same time, in an outdoor pot experiment, seeds of these legumes were sown approximately every 3 weeks and seedling emergence dates were determined. The predicted dates of seedling emergence generally fitted the observed dates. Another prediction was attempted using the base temperatures, thermal constants, and normal daily mean air temperatures recorded over more than 30 years in the study site. This prediction showed that the seedlings of the three forage legumes began to emerge at the beginning of April and could continue to emerge until the beginning of November when their non‐dormant seeds were present in the site, and that when the seeds were sown from mid‐November of one year to late March of the next year, the emergence of seedlings was delayed until the beginning of April.