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1.
Four varieties of white clover (small-leaved cv. Aberystwyth S184. medium-leaved cv. Grasslands Huia and large-leaved cvs Linda and Olwen) were sown at 3 kg ha-1 together with 10 kg ha-1 perennial ryegrass cv. Talbot. Herbage productivity was measured for three harvest years, 1979-81, over four annual rates of fertilizer N (0,120,240 and 360 kg ha-1) and two closeness of cutting treatments (80 and 40 mm from ground level). A simulated grazing regime of six cuts per year at 3- to 6-week intervals was used.
Production of total herbage DM was increased by increasing N rate; mean annual DM production ranged from 783 1 ha-1 with no N to 11701 ha-1 at 360 kg ha-1 N. Mean herbage response to N (kg DM per kg N applied) was 73,90 and 108 for the three successive N increments relative to no N. Mean white clover DM production was reduced from 4 14t ha-1 with no N to 051 t ha-1 at 360 kg ha-1 N.
The large-leaved clover varieties were more productive than the small- or medium-leaved varieties at all N rates. Close cutting increased total herbage and white clover by a mean annual 16% and 31%. respectively. White clover varieties did not interact with either N rate or closeness of cutting.
It is concluded that repetitive N application over the growing season is incompatible with white clover persistence and production, even with large-leaved clover varieties or with close cutting, two factors which improved clover performance in the experimental swards.  相似文献   

2.
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.  相似文献   

3.
In experiments to determine the minimum fertilizer requirements for improved pasture on deep peat, yields were initially low and declined rapidly. Within 2 years persistence of sown species was poor when only 2·5 t lime ha-1 was applied. Analytical data suggested that K deficiency and low soil pH were contributory factors. When K was omitted from a composite nutrient solution, clover yield was reduced by 50% when 2·5 t lime ha-1 was applied but was not significantly reduced with 5·0 t lime. Clover alone produced little response to either P or K separately, but highly significant positive interactions were recorded. Clover, but not ryegrass, responded to K topdressing in field cut-herbage experiments. There was a 3-fold increase in ryegrass yield with combined P and K topdressing under grazing; 10 times more N and K were recycled in urine on this treatment than on the control.
It was concluded that at least 5·0 t lime, 60 kg P and 80 kg K ha-1 are required for pasture establishment and that soil pH should be maintained above 5·0 to minimize K requirements. The significance of nutrient cycling and of lime × K and P × K interactions is discussed in relation to the persistence of sown species and the maintenance of improved swards on deep peat.  相似文献   

4.
A preliminary investigation evaluated six grass-suppressing herbicides applied on two occasions in late winter to a predominantly ryegrass ley containing only 15% ground cover of white clover. Substantial increases in clover growth, estimated visually, and flower head numbers per unit area were recorded in the first summer after treatment with 2·8 kg ha-1 carbetamide, 0·8 kg ha-1 propyzamide and 0·6 kg ha-1 paraquat. To achieve these increases, visual estimates suggested that spring growth of grass was reduced by 40–80%. However, grass growth recovered fully by mid-summer on the majority of the treatments.
The following year five of the herbicides were compared in a field experiment. Dry matter (DM) and nitrogen (N) assessments of the grass and legume components were made at three harvests in the first growing season and a single harvest in the second year. Carbetamide, paraquat and, especially, propyzamide increased the proportion of clover in the DM (to 89% in the case of 1·2 kg ha-1 propyzamide); in general, using herbicides to raise clover contents above 20% lead to reductions in spring grass growth of about 70%. However, such reduction was offset by subsequent increased growth so that total annual yields were largely unaffected. The increased legume content resulted in an increased N concentration in both grass and legume components, measured in the second summer. At this time, the greatest increase in total N yield (up to 35%) was recorded from 0·6 kg ha-1 propyzamide. Potential uses to achieve legume dominance by grass-suppression are suggested and the needs for further research are outlined.  相似文献   

5.
Applications of N fertilizer (0.40, 80, 120 and 240 kg N ha−1 year−1 in dressings of 40 or 80 kg N ha−1) were made to a perennial ryegrass/white clover ( Lolium perenne L. Trifolium repens L.) pasture growing on a humus iron podzol reclaimed from heather ( Calluna vulgaris L.) moor in 1982 and 1983. Where no N was applied, estimates of Ni fixation and mineralization were almost equal, being approximately 50 kg N ha−1 year−1 from each source. Apparent efficiencies of fertilizer use were generally low; for each dressing they ranged between –0·7 and 25·5 kg dry matter (DM)kgN−1. Also, responses to N fertilizer were affected by previous dressings. The net N recovery in harvested herbage from application of 120 kg N ha−1 year−1 was 30 kg N ha−1 year−1.  相似文献   

6.
Ninety-six plots (3 × 2 m) of well-established perennial rye grass/white clover pasture were mown to heights of 2·7 (Low) or 3·96 (High) cm (rising plate meter) at 14-, 28-, 84- or 112-d intervals in autumn-winter. A 7-, 14- and 28-d mowing interval was superimposed in spring on each autumn–winter mowing interval treatment with the low and high mowing heights altered to 2·92 and 4·80 cm, respectively.
With the low cutting height, accumulated herbage DM was more than doubled (1806 ± 79 kg DM ha-1) compared to a 'high' (754 ± 49 kg DM ha-1) cutting height in autumn–winter and this was due to increased harvesting efficiency rather than growth as estimated by leaf extension. Although defoliation interval had no effect on DM yield, the grass component increased and clover decreased. The composition effect carried over into spring. On average, 3·5 tillers were produced over winter for each ryegrass tiller present in autumn and tiller densities were higher in spring. Tillers produced over autumn–winter contributed more than 60% of ryegrass growth by early spring.
In early spring (16–30 September), the low cutting height increased herbage DM yield, in mid-spring (1–14 October) it reduced DM yields particularly in combination with short defoliation intervals, while in late spring (14 October to 11 November) cutting height had no effect on DM yields.
Over the entire spring period there was a very marked effect of defoliation interval on DM yields.  相似文献   

7.
Over three grazing seasons (1984-1986) a sward of perennial ryegrass, cv. Talbot, which received a total of 336 kg N ha-1 each season, was cut or grazed with ewes at 3- or 4-week intervals on a rotational basis.
Sward productivity was higher under cutting than under grazing irrespective of the interval between defoliations. Under cutting, mean herbage organic matter (OM) yields over both intervals were 8·66, 9·62 and 8·17 t ha-1 in 1984, 1985 and 1986 respectively while under grazing the corresponding yields were 7·65, 8·63 and 7·50 t ha-1. The mean annual yield of herbage defoliated at 3-week intervals was 7·50, 8·64 and 7 ·20 t OM ha-1 compared with 8·80, 9·60 and 8·46 t OM ha-1 for swards defoliated at 4-week intervals in the three years respectively.
The nitrogen (N) content of both the available and the residual herbage was consistently higher under grazing than under cutting. Available herbage contained 31·3 and 27·7 g N kg OM-1 and residual herbage 26·1 and 22·7 g N kg OM-1 under grazing and cutting respectively.
The mean yield of N under cutting was 284 kg ha-1 compared with 304 kg ha-1 under grazing. Defoliation interval had no effect on N yield, the overall mean yield being 294 kg ha-1 under both 3- and 4-week defoliation intervals. The effect of the treatments on tiller population was slight and inconclusive.
The process of grazing reduced yield probably as a result of damage to the sward through trampling; the positive effect of excretal N on yield was minimal on account of the short grazing periods.  相似文献   

8.
Three diploid red clover cultivars—Sabtoron, Violetta and Essex—and three tetraploid, Hungaropoly, Teroba and Red Head, were sown separately in pure culture and with each of three companion grasses: timothy (Aberystwyth S48), tall fescue (Aberystwyth S170) and perennial ryegrass (Aberystwyth S24).
The effects of fertilizer N on yield and on clover/grass ratio over a 2-year period (seventh and eighth harvest years) subsequent to 6 harvest years during which no N fertilizer was applied were investigated. The data for productivity and persistence have already been published (McBratney, 1981; 1984).
Application of fertilizer N increased DM yields in the eighth year. In this year, the highest yield, 11·9t ha-1, averaged over the six clover cultivars, was given in association with tall fescue. Tall fescue contributed 90% of this yield. Clover content continued to decrease in all swards but the decrease was greatest in the swards receiving fertilizer N. The yield of clover DM averaged over the six cultivars under N treatment declined from 5·6t ha-1 in the seventh year to only 0·4t ha-1 in the eighth year.
The results from this trial demonstrate the potential of red clover sown either pure or in mixture with a suitable perennial grass, to maintain high output of quality herbage over a 6-year period without the aid of fertilizer N. They further demonstrate that following decline in red clover content, both herbage yield and quality may be restored by the application of N fertilizer, particularly where the clover was seeded with a highly productive companion grass.  相似文献   

9.
The responses in dry matter (DM) production and changes in nutrient concentration in the shoots of white clover (cv. New Zealand Grasslands Huia) to additions of lime, N, P, K and Mg were investigated in pot and field experiments in a deep peat soil and to additions of N, P, K in two other hill soils in pot experiments. DM production and nutrient concentrations were assessed also for perennial ryegrass in the field experiment. There was no response by white clover to N, but in all soils, and in particular a deep peat, production of shoot DM was increased greatly by lime, P and K, and slightly by Mg. Interactions between lime and P and between P and K were observed. Critical concentrations of nutrients (g kg−1) for white clover appeared to be about 2.0 for P, 10·15 for K and 20 for Ca. Herbage production and nutrient contents of ryegrass and white clover grown on a deep peat in the field suggests that critical concentrations may possibly help to diagnose the need fur maintenance fertilizer dressings.  相似文献   

10.
Ryegrass/white clover pastures were reseeded on heather moor in north-cast Scotland in 1978/79. By 1981, despite moderate fertilizer applications, the pastures had deteriorated and dry matter (DM) production was low. After preliminary soil and herbage analysis an omission trial was carried out in 1982/83 at two sites (A and B) to identify the factors which limited production.
At site A depressions in growth occurred in the absence of N, P and K. Perennial ryegrass was severely N deficient with concentrations in leaves of less than 22 g N kg−1 in spring and summer even after application of 120 kg N ha−1 annually. Rates of nitrogen fixation were high in spring but rapidly declined in June and July as the soil moisture tension increased. Application of N fertilizer also reduced the N2 fixation rate. Deficiencies of F and K occurred despite apparently high levels of extractable F in the soil. Uptake of these nutrients was inhibited in the dry soil during the summer. White clover was more susceptible to drought than perennial ryegrass, probably because it rooted at a shallower depth.
Growth at site B was limited by acidity and lack of N and K. The soil pH was 4 8 (s.d. = 0middot;75) at 1-5 cm depth. Application of 2 5 t lime ha−1 in spring 1982 had not altered the pH by autumn 1983.
It was concluded that methods of incorporating lime into the soil, together with ways of increasing the rates of N2 fixation by white clover and transfer to grass, should be investigated further. Regular small applications of N and K may be necessary to sustain DM production at the level required by the farming system.  相似文献   

11.
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.  相似文献   

12.
Four management systems involving different dates for first harvest (simulated grazing, early silage, late silage and hay) and two fertilizer N rates in spring (0 and 80 kg ha-1) were imposed on a perennial ryegrass cv. Talbot/white clover cv. Blanca sward during 1981-82. In each year, annual total herbage DM was increased by spring application of N but white clover production and content in the total herbage were reduced; however, white clover, which was depressed in the harvests immediately after N application, recovered during the season to amounts and contents in the total herbage similar to those given no spring N.
Annual total herbage DM production increased as the date of primary harvest was delayed (935 to 1197 t ha-1 over two years) but mean organic matter digestibility values for the same period decreased (0-769 to 0700). First-harvest production made up substantial proportions of the annual production in the conservation systems. White clover, as shown by its production and the amount of stolon present, was tolerant of conservation systems, especially with no applied N.
It is concluded that grass/white clover swards are suitable for management systems which involve cutting for conservation. The use of strategic spring N seems a viable option, but more knowledge of rates would be valuable since this experiment only compared 80 kg ha-1 with no applied N.  相似文献   

13.
Herbage characteristics were studied over years 4–6 (1988–90) in three perennial ryegrass ( Lolium perenne L.) varieties as grass-only (200 kg N ha-1) and grass/clover ( Trifolium repens L.) swards which received 75kg N ha-1 in 1988 and 0kg N ha-1 in 1989 and 1990 when continuously stocked with sheep. Mean total annual herbage production of Aurora, a very early flowering variety, was 11% more than that of late-flowering Aberystwyth S23 due to 21% higher growth as grass/clover pasture. The grass/clover sward of Meltra, a tetraploid late-flowering variety, out-yielded S23/clover by 17%. Herbage production of grass/clover was 86% of that of grass only in 1988 but only 54% of the grass-only swards averaged for 1989 and 1990.
In vitro organic matter digestibility (OMD) of Meltra was 38g kg-1 OM and 27g kg-1 OM higher than that of S23 and Aurora respectively. OMD of grass/clover was 15g kg-1 OM higher than that of grass only during the post-weaning period. Herbage intake was positively correlated with OMD of herbage.
The herbage attributes were related to lamb performance reported previously. Lamb output was positively correlated with intake of digestible organic matter.
Differences between the three varieties in herbage characteristics were greater as grass/clover than as grass-only swards, reflecting their compatibility with white clover. In this respect Meltra was the best and S23 the poorest variety.  相似文献   

14.
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.  相似文献   

15.
The expected reduction in the use of fertilizer nitrogen (N) on grassland in the Netherlands has led to renewed interest in white clover. Therefore, the performance of a newly sown perennial ryegrass/white clover sward on clay soil was assessed during 4 consecutive years. The experiment consisted of all combinations of two defoliation systems, i.e. one or two silage cuts per year (S1, S2), spring N application rate, i.e. 0 or 50 kg ha−1 year−1 (N0, N50), and the management system, i.e. rotational grazing and cutting, or cutting only (RGC, CO). The overall mean white clover cover was 30%. All treatments affected white clover cover, which was 8% higher with S2 than with S1, 6% higher with N0 than with N50 and 12% higher with CO than with RGC. The overall mean annual dry-matter (DM) yield (13·1 t ha−1 year−1) was significantly affected only by the management system: in two relatively wetter years, the annual DM yield was 1·19 t ha−1 higher with RGC than with CO, whereas there was no difference in two relatively drier years. Nitrogen application increased the DM yield in the first cut by 7·0 kg kg−1 N applied, but had no significant effect on the annual DM yield. Herbage quality was not affected by the experimental treatments. The average in vitro organic matter digestibility was 0.801, and the average crude protein content was 193 g kg−1 DM. With the expected reduction in the use of fertilizer N, perennial ryegrass/white clover swards should be seriously considered as an alternative option to perennial ryegrass swards on these clay soils.  相似文献   

16.
Perennial ryegrass/white clover pastures were grazed at different times in the winter to study the effect of time of grazing on subsequent plant growth. In 1983–84, 1984–85, and 1985–86, pastures were grazed to a residual of 400 kg dry matter ha-1 by sheep once in early December (D), January (J), February (F), March (M), or April (A) and compared with an ungrazed control (C). Rates of herbage accumulation on C in the winter were low, averaging 6, -9, and 2 kg dry matter ha-1 in December, January, and February, respectively. Little forage production occurred during the month immediately following winter grazing. Herbage accumulation rate then increased sufficiently to replace the forage removed from winter-grazed paddocks by early spring. By May, herbage mass on grazed treatments was similar to C except for D and A which averaged 20 and 47% less forage than C, respectively (P<0·01). Herbage accumulation rates of D were unique among winter grazing treatments in never exceeding those of C. By May 1986, D yielded less perennial ryegrass compared with C (P<0·05). Grazing reduced the number of leaves per ryegrass tiller for 1 to 2 months following grazing. By May, J, F and M had numerically more tillers m-2 and more leaves per tiller than C. Similar May yields of J, F, M, and C resulted from fewer but larger and slightly less leafy tillers of ungrazed compared with winter grazed plants.  相似文献   

17.
The effect of applying 100kg P ha-1 per year in the form of triple superphosphate to mixed swards of perennial ryegrass ( Lolium perenne ) and white clover ( Trifolium repens ) was examined on a soil of low P status.
The dry matter yield of total herbage was increased by 10'/i by added P. In the year of sowing the ryegrass benefited more than the clover from added P: in the subsequent four years the two species benefited equally. Both species responded 10 added P to a similar extent in terms of leaf size; the clover responded less well than the ryegrass in terms of rate of leaf emergence. However, clover responded positively to added P in terms of stolon internode length, length of stolon per m2 and number of growing points per m2. It is suggested that the application of P may promote the spread of white clover within an open sward, but that its application may not enhance the competitive power of white clover when growing with vigorous grasses.  相似文献   

18.
The effects of delayed emergence of white clover (cv. Grasslands Huia) seedlings, following slot-seeding during spring and early summer 1983, were simulated by sowing seeds at intervals into slots cut in turves of permanent grassland in soil-filled tanks or in the field. The resulting spread and growth of the species were assessed during the following 15–18 months. The effects of propyzamide, a grass-suppressing herbicide (at 0·2 kg ha-1), were also investigated in the field.
A delay of 10 or 18 days in the sowing of seeds in turves in the tanks reduced clover dry weight yield from 23 to 11 during 1983 and from 118 to 96 g (0·12 m)-2 during 1984. Spread of stolons from the slots was also greatly delayed and effects persisted for at least a year. Increased clover growth on the earliest sown treatment more than compensated for a slightly smaller yield of grass.
In the field, yields of clover from late summer 1983 until spring 1984 closely reflected the order of emergence. Afterwards, differences were less clear-cut but the cumulative yield of clover until August 1984 of the earliest-sown treatment was twice that of a treatment sown 20 d later. Effects of delayed sowing in summer 1983 were more pronounced on stolons than on foliage growth when measured in September 1984, with significant reductions in many stolon attributes even with 8 d delay in sowing. Application of propyzamide in autumn 1983 increased clover yield during 1984 from 1·7 to 3·0 and total herbage yield from 7·1 to 8·6 t ha-1.
The results demonstrated some of the benefits of rapid seedling emergence and of the use of a grass-suppressing herbicide, but did not indicate any interaction between the two factors.  相似文献   

19.
Effects of timing and rate of N fertilizer application on concentrations of P, K, S, Ca, Mg, Na, Cl, Mn, Fe, Cu and Zn in herbage from perennial ryegrass/white clover pastures were studied at two sites in south-western Victoria, Australia. Nitrogen fertilizer (0, 15, 25, 30, 45 and 60 kg ha–1) was applied as urea in mid-April, early May, mid-May, early June and mid-June 1996 to pastures grazed by dairy cows. At Site 1, N fertilizer resulted in a linear increase in P, K, S, Mg and Cl concentrations in herbage and a linear decrease in Ca concentration. For all times of application, concentrations of P, K, Ca, Mg and Cl in herbage increased by 0·0048, 0·08, −0·010, 0·0013 and 0·053 g kg–1 dry matter (DM) per kg N applied respectively. For S concentration, maximum responses occurred in mid-May (0·012 g kg–1 DM per kg N applied). At Site 2, N fertilizer resulted in a linear increase in P, S and Na concentrations in herbage, a linear decrease in Ca concentration and a curvilinear increase in K and Cl concentration. The maximum responses for P, S and K concentrations in herbage occurred for the N application in mid-June and were 0·015, 0·008 and 0·47 g kg–1 DM per kg N applied respectively. For Cl concentration, the maximum response occurred for the N application in early June and was 0·225 g kg–1 DM per kg N applied. Overall, applications of N fertilizer up to 60 kg ha–1 did not alter herbage mineral concentration to levels that might affect pasture growth or animal health.  相似文献   

20.
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.  相似文献   

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