bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of fertilizer nitrogen on six‐year‐old red clover/perennial grass swards
Authors: McBRATNEY JUNE M.
Published: April 2006

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.
Microscopic and chemical changes during the first 22 days in Italian ryegrass and cocksfoot silages made in laboratory silos
Authors: WINTERS ANA L. , WHITTAKER P. A. , WILSON R. K.
Published: April 2006

Although many aspects of grass silage have received intensive study, the changes that take place within the grass blades during ensilage have received little attention.

In two factorial experiments Italian ryegrass (cv. Lemtal) and cocksfoot (indigenous) were ensiled in laboratory silos (capacity 0·2 kg) with the grass under pressure (700 Pa) and subjected to two treatments (with or without 3·31 t‐1 85% formic acid) and two silos from each treatment opened on eight sampling dates(1,2,3,4,7,10,14 and 21 d).

For each sampling date transverse sections of grass laminae were examined and changes in the cross sections of the protoplasts and of cells, as defined by the cell walls, were recorded. These data were used to calculate the ratios of protoplast to cell volumes at each sampling date.

Each silage was analysed for dry matter, pH, lactic acid, VFA, ammonia and glucose. The distance settled by the silage (a measure of decrease in silage volume) and the silage conductivity were also recorded.

Both of the untreated grasses yielded silages with typical lactic acid levels and pH values. In all of the silages there was a marked shrinkage of the plast within the space defined by the cell wall. The ratio of protoplast to cell volume eventually stabilized at 0·4. The formic acid‐treated grasses reached this level by day 1 but a longer period was required by untreated grasses.

It is suggested that the decrease in silage volume is related to the lactic acid content of the liquid phase due to their close relationship in silages produced from untreated grasses (r= 0·97***).
Comparative sheep production and herbage characteristics on four perennial ryegrass varieties in the uplands
Authors: DAVIES D. A.
Published: April 2006

Ewe and lamb performance, herbage production and feed quality components on four late‐flowering perennial ryegrass (Lolium perenne L.) varieties were assessed under a fixed stocking management at an upland site (305 m OD) in mid‐Wales. Averaged over four years (1981–84) there was no significant difference (P>0·05) between Aberystwyth S23, Aberystwyth Ajax, Perma and Meltra (tetraploid) in ewe and iamb liveweight gains. There were, however, considerable differences between varieties during individual years and their relative ranking also changed substantially over the four years. Lamb production on Perma was 22% more than on S23 in the first year but by the fourth year it was 21 % less than on the latter variety.

Differences between varieties were observed in herbage production. Net herbage accumulation was 15% more on Meltra than on Ajax whilst the calculated quantity of OM consumed was 19% higher from Meltra than from both Ajax and S23. Net animal liveweight gains were positively correlated with herbage production (r = 0·95, P < 0·05) and DOM consumed (r=0·96. P<0·05).
Forage production and quality of several crop rotations and pastures in northwestern Spain
Authors: LLOVERAS‐VILAMANYA JAIME
Published: April 2006

Multiple cropping has been used for many years to increase production in temperate areas of Europe where the growing season is favourable and is important when land area is limiting.

The purpose of this 3‐year study was to determine how several different cropping systems affected forage production potential at three rainfed locations in northwestern Spain (Galicia). The cropping systems compared were: single crop maize; double crop systems of maize‐rye, maize oats+ vetch, and maize‐Italian ryegrass; three crops in a two‐year rotation of maize‐Italian ryegrass (12‐months) forage rape; 2‐year pasture maize and two contrasting 3‐year grass‐legume mixtures.

There was an increase in dry matter (DM) production as cropping intensity increased. The one‐year double cropping systems always yielded more than three crops in two years, which in turn outyielded single crop maize or 3‐year pastures. The highest DM yields were 20–9 t ha‐1 from the maize‐oats‐I‐vetch rotation. Maize was the principal crop determining total production, yielding about 70% of the total DM for the double cropping systems. The maize component gave similar annual yields in the multiple crop and maize‐pasture rotations, but the use of maize allowed double cropping, which increased production compared with 3‐year pasture.

Forage rape gave the highest in vitro dry matter digestibility (IVDMD) of 773–815 g kg‐1 while the oats‐I‐vetch mixture gave the highest crude protein (CP) concentration (105‐217 g kg‐1). The maize crops had the lowest CP content (62‐76 g kg‐1) though digestibility was high (653‐713 g kg‐1).
Studies on the estimation of sampling error for leatherjackets (Tipula spp.) in grassland
Authors: BLACKSHAW R. P.
Published: April 2006

Leatherjacket populations were sampled from 20 sites in Northern Ireland by collecting 10 cm diameter soil cores and wet sieving. The sample variances were linearly related to the sample means. Up to a mean of 1.14 leatherjackets per core, populations could be described by the Poisson distribution. Negative binomial distributions could also be fitted to data where the sample variance was greater than the sample mean. A strong curvilinear relationship was found between the sample mean and the proportion of cores containing leatherjackets. The raw data were used to generate a series of equations which in turn gave rise to a function linking frequency, sample mean and sample size.

The implications of these results are discussed in relation to population estimation and advice to farmers.
The effect of subsequent mangement on the success of introducing white clover to an existing sward
Authors: SHELDRICK R. D. , LAVENDER R. H. , PARKINSON ANN E.
Published: April 2006

Two experiments, each lasting approximately 12 months, were carried out at North Wyke, Devon, in 1982‐83 (A) and 1983‐84 (B), to investigate various sward managements following oversowing of white clover (Trifolium repens, cv. Grasslands Huia) at 4 kg ha‐1 with a Hunter Rotary Strip‐Seeder in June or July into the stubble of a permanent grass sward following conservation. Experimental managements comprised cutting, grazing with wether sheep or grass suppression by herbicide, as appropriate, in late summer/autumn (Phase I), winter (Phase II) and spring/early summer (Phase III).

During Phase I, there was no differential effect on clover stolon development of lenient grazing at approximately 4‐weekly intervals or topping at the same frequency to a similar height. Early in Phase II of Experiment A, grazed paddocks became so badly poached that no differences occurred between grazing either to early January or throughout the winter. Under drier conditions in Phase II of Experiment B, continuous grazing at either five (L) or ten (H) sheep ha‐1 had no immediate effect on clover stolon development, but in a silage cut in June, paddocks formerly stocked at the lower rate yielded 40% more DM than those at the higher rate.

Experiment A compared the use of a grass‐suppressing herbicide, propyzamide, applied at 0.6 kg a.i. ha‐1 in either October or February; in Experiment B it was applied in October. Prophyzamide applied at either time in Experiment A increased the clover content of herbage regrowing after the end of the experimental period from 16% to 36% (s.e.d. ± 3.9). In Experiment B, October application raised the clover contents of herbage cut in June 1984 from 10% (H) and 17% (L) to 32% (s.e.d.±5.9), and stolon lengths per m2 at the end of the summer period from 33 (H) and 56 (L) to 86m (s.e.d. ± 11.7). However, the effect of spraying propyzamide on subsequent herbage yields was erratic, and appeared to depend on the incidence of frost after application.

In Phase III of Experiment A, continuous grazing was compared with a silage cut in June. At the end of the experiment there were 31 m m‐2 of clover stolon in silaged areas compared with only 2.5 m m‐2 following grazing (s.e.d.±6.6). Clover content and herbage yields were also significantly higher following conservation. In Experiment B in the same period, rotational grazing with a 14‐ or 35‐day recovery interval was compared with a silage cut in June, with or without 100 kg N ha‐1 applied in March. Application of N to the conservation treatment reduced clover stolon length per unit area, and in the regrowth in the post‐experimental period the conservation treatment without N had the largest clover content (31% compared with 16‐23% for other treatments, s.e.d. ± 3.6)
Tillering and leaf area index in grasses in the vegetative phase
Authors: SIMON J. C. , LEMAIRE G.
Published: April 2006

The relationship between tillering of a vegetative grass stand and Leaf Area Index (LAI) has been studied during sward establishment of perennial ryegrass and Italian ryegrass with different seedling densities and nitrogen fertilizer rates and on established swards of tall fescue during winter and early spring after different dates of last cut in autumn.

The different experiments on different species led to the conclusion that in every instance the tillering rate slows down as soon as the LAI reaches a value of 3 and terminates rapidly at higher LAI, which corresponds with the almost complete extinction of light at the level of the tiller buds. The results confirm the direct role of light on morphogenesis previously demonstrated by several authors. The existence of such a limit of LAI helps to explain some contradictory effects of temperature or nitrogen on tillering.
Factors affecting the leaf extension rate of perennial ryegrass in spring
Authors: BAKER ANNE‐MARIE , YOUNGER A.
Published: April 2006

The effects of soil temperature and other factors on the early spring growth of perennial ryegrass (Lolium perenne) swards were studied in 1983, 1984 and 1985. Leaf extension was used as the measure of growth and soil temperature was recorded at 10 cm depth below bare ground. Measurements were taken before the first nitrogen dressing had been applied each spring on swards that had received annual dressings of 0, 200 or 400 kg N ha‐1 since 1982.

On the pooled data temperature alone accounted for 604% of the variation in leaf extension rate, with an average increase of 0·4 mm d‐1 for each 1°C increase in temperature over the range studied. Considering the data for each year separately did not greatly improve the correlation but did indicate that leaves extended more rapidly in 1985 for each degree increase in temperature whereas the smallest response was recorded in 1984. A better correlation was achieved by grouping data according to the nitrogen rates previously applied to plots and there was evidence of residual effets of this nitrogen. It seems likely that the differences between years can be explained in terms of differences in radiation and other environmental parameters over the measurement period, whereas the effects of previously applied nitrogen may be more closely related to physiological changes in the sward.
The deposition of Caesium 137 on grassland at a site in SW England following the Chernobyl accident
Authors: GILBEY J. , BRADLEY S. , WALLING D. E.
Published: April 2006

Following the Chernobyl accident in April 1986 137Cs was detected in samples of grass collected at AGRI, North Wyke, Devon, UK. Samples of grass from permanent and reseeded swards under uniform management were taken on three occasions. The 137Cs content of the samples was assessed as both Bq kg‐1 of sample and Bq m‐2, Samples taken from the same site in 1985 were used as a control group; these contained no measurable 137Cs. The samples taken on 8 May 1986 had a 137Cs content of approximately 30 Bq kg‐1; by 31 July 1986 the content had dropped to 1% of this value. The permanent pasture initially showed a higher level of 137Cs than the reseeded sward. Analysis of soil cores from the sampling area showed a much higher level of 137Cs than that found in the herbage. This was attributed to the atmospheric testing of nuclear devices in the early 1960s: the short‐lived 137Cs isotope was found in the 1986 herbage samples but not in the soil cores.
Variation in spring temperatures, grass production and response to nitrogen over twenty years in the uplands
Authors: DAVIES D. A. , MORGAN T. E. H.
Published: April 2006

Large between‐year variation was observed in spring air and soil temperatures at Pant‐y‐dwr Hill Centre (305 m altitude) from 1967 to 1984 and at Bronydd Mawr Research Centre (330 m) from 1985 to 1986 in Powys. The mean date of attaining T‐sum 200°C accumulated air temperature was 13 March (range 9 February to 23 April) and that of soil temperature at 100 mm depth permanently above 5 5°C was 9 April (range 7 March to 4 May). Net herbage accumulation and response to applied N from Aberystwyth S23 perennial ryegrass (Lolium perenne L.) swards during April were also highly variable and were correlated with the date of reaching target soil temperatures of above 5 5°C for 5 consecutive days (r=−0·68, P < 0·001 for net herbage accumulation and r=−0·70, P < 0·001 for response to N).

The use of early flowering varieties of perennial ryegrass gave a significant increase of herbage growth in spring compared with late varieties. From 1979 to 1980 net herbage accumulation during April from the early variety Frances was 94% more than from Perma (late) and 55% more than from Talbot (intermediate) varieties. Under conservation management more winter hardy and persistent varieties of Italian and hybrid ryegrasses (L. multiflorum L. and L. multiflorum X L. perenne) gave higher quantities of firstcut silage crops in early June than RvP Italian ryegrass.

After the severe winters of 1978–79 and 1985–86, subsequent spring production from a wide range of ryegrasses was shown to be affected by sward survival, highlighting the value of winter hardy varieties when resowing in the uplands
Seasonal patterns of grass production under cutting or continuous stocking managements
Authors: ORR R. J. , PARSONS A. J. , TREACHER T. T. , PENNING P. D.
Published: April 2006

A comparison was made between the seasonal pattern of net herbage accumulation under cutting and the pattern of intake under continuous variable stocking on a Lolium perenne sward, which was well supplied with nitrogen fertilizer and irrigated to minimize moisture stress.

The seasonal pattern of production under monthly cutting showed characteristic asymmetry with a marked peak in production in late May/early June, a rapid decline in June followed by an increase in rate in August and the total amount harvested over the season was 9–28 t organic matter ha−1.

By contrast, the seasonal patterns of production on swards grazed by ewes to maintain sward surface heights of 30, 50 and 70 mm all differed fundamentally from that observed under cutting. Production was more evenly distributed throughout the season under these grazing treatments which, it has been proposed, should optimize performance. Total amounts harvested by grazing were 10–84, 10.12 and 8.51 t OM ha−1, respectively. The different patterns of production under cutting and grazing were considered to be associated with differences in the expression of reproductive development in the grass crop and the maintenance of a smaller leaf area per unit ground area under grazing.

The results of the study suggest that it is not appropriate to regard the seasonal pattern of net accumulation under a standard cutting regime as representing the potential production of grass under continuous stocking. Moreover, in practice, the more uniform seasonal pattern of production seen in swards maintained on the basis of a controlled sward surface height makes it easier to match the supply of herbage to the appetite of grazing animals as the season progresses.
Competition among seedlings of phalaris, subterranean clover and white clover in diallel replacement series mixtures
Authors: HILL M. J. , GLEESON A. C.
Published: April 2006

Phalaris, subterranean clover and white clover were grown together in binary, diallel replacement series mixtures at (day/night) 15/10 or 24/19°C under long‐day conditions, and cut at 2‐ or 4‐weekly intervals. Analysis of white clover mixtures was confined to 15/10°C due to losses of seedlings prior to imposition of treatments at 24/19°C.

With white clover at 15/10°X, seedling losses occurred after the first harvest, the greater losses occurring in mixtures where subterranean clover was the major component. The de Wit analyses showed that subterranean clover excluded its companions, whereas phalaris and white clover competed for slightly different niches resulting in over‐yielding. Gleeson McGilchrist analyses showed that subterranean clover and phalaris were more aggressive than white clover under infrequent cutting, but that white clover was more aggressive as a major than as a minor component of a mixture under frequent cutting. Between phalaris and subterranean clover [he pattern of competition at 24/19°C differed from that at 15/10°C only in the more rapid development of subterranean clover and consequent swing to phalaris dominance.

We conclude that the seedlings of white clover and subterranean clover are suited to combination with phalaris because phalaris is not too aggressive towards white clover, and is tolerant of the aggressiveness of subterranean clover. The survival of only a few seedlings of white clover in mixtures with subterranean clover may be sufficient for long‐term growth provided some perennation occurs after the senescence of subterranean clover.
The effects of feeding fodder beet with two levels of concentrate allocation to dairy cattle
Authors: SABRI M. S. , ROBERTS D. J.
Published: April 2006

Twelve cows were used in a cyclic changeover design experiment to examine the effects of feeding fodder beet (variety Kyros) at three levels (0, 2 and 4 kg dry matter (DM) d−1) with two levels of concentrate feeding (4 and 8 kg DM−1). Silage was offered ad libitum. At the start of the experiment the mean number of days after calving was 46 and the mean live weight 516 kg. The experiment consisted of four 3‐week periods with intake and performance measurements during the last week of each period.

An in vitro analysis of the feeds for the silage, fodder beet and concentrate respectively was: DM (g kg‐−1) 189, 163, 860; crude protein (g kg DM−1) 143,76,201; metabolizable energy (MJ kg DM−1) 104, 133, 13–5.

Silage DM intake decreased but total DM intake increased when fodder beet was fed. The DM intakes (kg d−1) for treatments (fodder beet/ concentrate) 0/4, 2/4, 4/4, 0/8, 2/8, 4/8 respectively were: silage DM 91, 79, 78, 83, 70 and 68 (s.e.d. =0.31); and total DM 130, 138, 156, 162, 166, 183 (s.e.d. = 0.36). Feeding fodder beet had no significant effects on milk yield or milk composition, but there was a significant increase in milk protein yield when fodder beet was included in the ration. There were no significant interactions between level of fodder beet feeding and concentrate level. Increasing the level of concentrate feeding led to a highly significant increase in milk yield, milk protein content and yield of milk constituents. The yields for treatments 0/4, 2/4,4/4,0/8, 2/8,4/8 respectively were: milk yield (kg d−1) 206, 204,21 8, 241,235, 244 (s.e.d. = 0–58); fat yield (g d−1) 827, 793, 885, 954, 936, 954 (s.e.d. = 394); and protein yield (g d−1) 622, 628, 679, 774, 777, 814 (s.e.d. = 179). There were no significant differences in milk yield and milk composition when fodder beet was included in the diet which may have been due to the low crude protein content of the diet.
On the analysis of dacron bag data for low degradability feeds
Authors: DHANOA M. S.
Published: April 2006

The effect of lag phase on the estimates of parameters from the analysis of dacron bags is investigated. Simultaneous estimation of the lag parameter within the McDonald model is shown to be advantageous.
The effect of the duration of regrowth on photosynthesis, leaf death and the average rate of growth in a rotationally grazed sward
Authors: PARSONS A. J. , PENNING P. D.
Published: April 2006

A study was made to characterize the effect of the duration of regrowth on the pattern of changes in the major physiological processes involved in the net accumulation of herbage, and so to provide a rational basis for optimizing production under rotational grazing.

During regrowth following a severe defoliation, rates of canopy photosynthesis, and so the rate of production of new leaves, increased rapidly but there was a delay before there was a corresponding increase in the rate of leaf death. Although the amount available for harvest (crop live dry weight, W) continued to increase as the duration of regrowth was extended from ‘short’ (12–13 days), through ‘medium’ (19–23 days) to ‘long’ (30‐34 days), there was not a continued increase in the average growth rate – the increase in the weight of the crop, (W – Wo), divided by the duration of regrowth, t, In this study, the average growth rate (based on changes in the weight of lamina alone) increased as the duration of regrowth was extended from 12‐13 to 19‐23 days but changed little as the duration of regrowth was extended from 19‐23 days to 30‐34 days. In spring and summer, elongating stems increased the average growth rate (of lamina plus stem) up to 30‐34 days but the accumulated stem material could not reliably be harvested by sheep.

A mathematical model was used to explain why the average growth rate is characteristically insensitive to the duration of regrowth beyond a given minimum duration. For practical purposes, we suggest from the results of this study that regrowths of at least 14 days but less than 28 days will be effective in achieving not only close to the maximum average growth rate of highly digestible material, but also in sustaining a densely tillered, leafy sward which regrows rapidly from severe defoliation and is more reliably harvested (utilized) by sheep.
Comparison of herbage production under continuous stocking and intermittent grazing
Authors: GRANT SHEILA A. , BARTHRAM G. T. , TORVELL LYNNE , KING J. , ELSTONJ D. A.
Published: April 2006

The possibility of increasing the herbage utilized over a grazing season was investigated in a study comparing continuously stocked steady‐state swards maintained at optimum height (3.5 cm) with intermittently grazed swards. The intermittent systems were designed (a) to allow periodic increase in leaf area and hence growth rate, (b)to ensure that the accumulated herbage was eaten before it senesced, and (c) lo retain high tiller density by alternating periods of herbage accumulation with periods of continuous stocking.

Two treatments (no animals or animal numbers reduced to half those on the 3.5 cm steady‐state treatment) were used during the 17‐18‐d periods of herbage accumulation. Grazing down was completed in 3–4 d, after which two treatments (14 d or 28 d) were used for the intervening periods of continuous stocking when sward height was maintained at 3.5 cm.

Herbage production was estimated using the tissue turnover technique, with tiller population densities and rates of growth, senescence and net production per tiller measured at frequent intervals.

Intermittent grazing treatments where animals were removed during herbage accumulation resulted in changes in tiller size and number, and in growth rates, but not senescence rates, per tiller such that short‐term deviations in the net rate of herbage production occurred compared with the continuously stocked control. The periods of advantage during phases of herbage accumulation were counterbalanced by those of disadvantage during the subsequent steady‐state phases. Where animal numbers were reduced during herbage accumulation, sward conditions differed little from those of the continuously stocked control, implying that intake per individual animal was increased.

It was concluded that intermittent grazing systems offered no advantage over simpler continuous stocking systems, provided that a flexible approach to conservation was incorporated to allow control of sward conditions on the grazed area.
The use of conserved forage as a supplement for grazing dairy cows
Authors: PHILLIPS C. J. C.
Published: April 2006

The difficulty in matching the herbage requirements of grazing dairy cows to herbage production, due mainly to the unpredictability of the latter., causes stocking rates to be too low for maximum per hectare production and, thus, cows to be underfed at certain times in the grazing season. Conserved forage may be used as a supplement for grazing dairy cows in order to reduce variation in forage intake by the cow, to allow pasture stocking rates to be increased and to increase the efficiency of land use. The effect of offering conserved forage with herbage on intakes and production is reviewed in comparison to both ad libitum and restricted herbage. Total nutrient intakes and milk fat + protein yields are reduced for cows offered herbage and supplementary forage compared with cows offered ad libitum herbage, but increased compared with cows offered a restricted herbage level. Increasing pasture stocking rates may allow increases in utilized metabolizable energy levels from grassland but further research is needed in this area. Both grass and maize silage supplements offer potential for increasing the efficiency of land use, but in the case of grass silage this is only achieved in the best management practices.
Influence of defoliation regime on herbage production and characteristics of intake by dairy cows as affected by grazing intensity
Authors: KRISTENSEN E. S.
Published: April 2006

Three contrasting defoliation regimes for dairy cows—four cuts annually, severe rotational grazing and lax rotational grazing integrated with cutting—were compared in terms of herbage production, selection and intake per cow. Lax and severe grazing were compared simultaneously and grazing intensity was characterized by means of changes in herbage mass and sward height during grazing.

Herbage growth and yield were similar under cutting, severe grazing and lax grazing/cutting (120 t organic matter (OM) ha−1). Herbage quality and leaf production were highest with severe grazing, which also had a less marked seasonal pattern of growth. The herbage intake per cow was 111 kg OM d−1 with severe grazing and proportionately (0‐20) higher at lax grazing/ cutting. 050 of the herbage yield was harvested by cutting at lax grazing/cutting. Selectivity was described with high certainly by the nutrient content prior to defoliation and by the degree of defoliation. Models to quantify this are presented.

Grazing intensity could be described by the size and degree of utilization of the fouled area, and herbage intake was quantified by means of herbage height before and after grazing. Within the range of 80‐240 mm sward height prior to grazing, height measurements led to realistic and more accurate estimates than those obtained by measuring organic matter disappearance.

Herbage utilization was depressed significantly by increasing maturity of herbage due to lower nutritive value, but in particular due to reduced green leaf content and increased reproductive development. If sward height did not exceed 250 mm at any time, good utilization by grazing could be obtained.
Variation in cold tolerance in Festuca rubra L.
Authors: McHUGH S. , HUMPHREYS M. O. , McNEILLY T. , JOHNSON M. S
Published: April 2006

A laboratory assessment was made of cold tolerance in seven cultivars and one natural population of red fescue, overwintered at lowland (30 m a.s.I.) or an upland (300 m a.s.l.) site.

After 5 months overwintering, plants were exposed under laboratory conditions to seven freezing temperatures, –7, –9, – 10, – 11, – 12, – 13 and – 15°C and + 2°C as control. Thawed tillers were grown in soil in glasshouse, and tiller survival and growth recorded after 28 days. Cold tolerance was estimated using LT50 values.

Tiller mortality increased with decreasing freezing temperature, with almost all tillers surviving at – 7°C and almost all dying at – 15°C. Cold hardening at the overwintering site markedly affected survival, plants overwintered at the upland site having significantly greater survival than those overwintered at the lowland site. All samples were affected to similar extent by overwintering site. The samples Aber Valley, Hawk, Merlin, Polar, and Dawson were significantly more cold tolerant than Jupiter, S59, and Highlight. Tiller production data closely resembled those for tiller survival.

For upland situations, eultivars or natural populations other than the currently recommended S59 have better cold tolerance, and may provide useful genetic resources for breeding cultivars for uplands use.
The effect of drainage on herbage growth and soil development
Authors: BAKER ANNE‐MARIE , YOUNGER A. , KING J. A.
Published: April 2006

The effects of drainage on the yield of perennial ryegrass (Lolium perenne) swards grown for silage, and on soil development under grassland, were studied between 1982 and 1985.

Over the 4 years of the experiment, drainage resulted in a mean increase in herbage production of 1‐5 t dry matter (DM) ha−1, 16% above the yield recorded on the undrained site. Drainage also led to increased herbage nitrogen contents at every cut except one, so that total nitrogen recovery was increased by an average of 24‐8 kg N ha−1 (15%) when drainage was installed. These total differences were mainly due to differences that were present at the first cut taken in June each year; drainage led to an average 24% increase in yield, and an average 27% increase in nitrogen recovery at the first cut.

Detailed sward measurements taken in 1985 endeavoured to explain these differences; drainage increased depth to free water over winter, enabling increased root efficiency and nitrogen availability, greater tillering and more rapid leaf extension in early spring. There was some suggestion that drainage also led to an improved topsoil structure in terms of improved aggregation and aeration. This is important for long‐term soil development as well as short‐term herbage yield.
The effect of wilting and silage additives on the fermentation of autumn made grass silage ensiled in bunkers on commercial farms in South Wales 1983‐85
Authors: HAIGH P. M.
Published: April 2006

Silage making practices in respect of 130 samples of autumn made grass silages ensiled in bunkers on commercial farms in South Wales during 1983‐1985 were analysed to discern the effect of wilting and/or silage additives on fermentation. Silages were primarily made during late September and early October in fine weather from perennial ryegrass pasture which had not been grazed for 6 weeks. On average 13.9 ha of pasture was cut for silage. Analysis of 120 samples of grass showed it contained 176 g kg−1 dry matter (DM) with (g kg−1 DM) 215 protein, 240 modified acid detergent fibre (MADF), 78 water‐soluble carbohydrate (WSC) and 95 ash. Most farmers attempted to pre‐wilt grass for 1 day prior to ensilage and one quarter of them made unwilted silage. Silage making was usually completed within 6 days of starting to cut and was generally made with a precision‐chop machine. Silage additives applied were (kg t−1) formic acid (4·7), formic acid 4‐formalin (5·5), sulphuric acid‐+ formalin (5·0) sugars (14) and inoculants (0·65). Formic acid significantly reduced pH, and formic acid with or without formalin significantly reduced ammonia nitrogen (N) content of silages compared with other treatments. Protein contents of acid/formalin treated silages were significantly higher and MADF of acid with or without formalin treated silages were significantly lower than other treatments. Pre‐wilting grass prior to ensilage did not significantly increase subsequent silage DM content and significantly increased the pH of non‐additive treated silages. Unwilted silages treated with formic acid with or without formalin had a significantly lower ammonia‐N content and higher residual WSC than other treatments.

It is suggested that only formic acid application either alone or in conjunction with formalin to unwilted silage was successful in producing well preserved silages and that a grass WSC content of 17 g kg−1 would be necessary to achieve this.
Growth of Trifolium repens L. and Trifolium semipilosum Fres. Var. glabrescens Gillet at different temperatures in controlled environments and in the field
Authors: Hill M. J.
Published: April 2006

The growth of Trifolium semipilosum Fres. var. glabrescens Gillet cultivar Safari, and Trifolium repens L., cultivars Haifa and Grasslands Huia was compared in controlled temperature glasshouses at 15/10, 21/16, 27/22 and 33/28°C (day/ night), and over eighteen months under four‐weekly cutting in the field. In glasshouses, white clovers grew better than Safari at all temperatures except 27/22°C. Stolon production and partitioning of dry matter to stolons was greater, and petiole production and partitioning of dry matter to petioles was less for Safari than for white clovers. Haifa and Huia differed primarily in individual leaf weight, individual leaf area and leaf numbers; with Hula and Safari, but not Haifa, exhibiting a reduction in leaf size in response lo defoliation. In the field, growth of Safari was poor. Growth responses of Haifa and Huia in the field were related to seedling vigour, dry matter partitioning between leaves and stolons, and response to defoliation at low temperatures. It was concluded that there were major differences in growth, dry matter partitioning, morphology and response to temperature between T. semipilosum and T. repens. These differences particularly influence climate adaptation and competitive ability at the seedling stage.
The use of growth regulator RSW0411 in seed crops of Lolium perenne L.
Authors: WILTSHIRE J. J. J. , HEBBLETHWAITE P. D. , ESSLEMONT R. E. , McGILLOWAY D. A.
Published: April 2006

Field trials were conducted in 1985 and 1986 to assess the effects of the growth regulator RSW0411 on a Lolium perenne L. (perennial ryegrass) seed crop. Applications were made at spikelet and floret initiation, and at 1, 2, 3 and 4 kg active ingredient ha−1.

Seed yield increases in 1985 were associated with increased reproductive tiller numbers and seed numbers, but in 1986 there were no seed yield responses.

Lodging was less severe in 1986, and there was less secondary filtering during seed maturation. In 1985, fertile tiller numbers were lower in control plots at harvest. These results are discussed in relation to the seasonal disparity in seed yield response.

RSW0411 application significantly decreased culm lengths by shortening the basal internodes, and this effect was greater with higher application rates. Stem width was increased in 1985 at the base and middle of the stem, and earlier applications increased the basal width by more than later applications.

Germination was not affected by RSW0411 treatment, except when applied at 4 kg active ingredient ha−1 in 1985, when there was a small decrease. This was related to a low 1000‐seed weight, and is discussed in relation to seed maturity at harvest.
Frequency of stocking rate adjustments required on contrasting upland perennial ryegrass pastures continuously grazed to a sward height criterion from May to July
Authors: DAVIES D. A. , FOTHERGILL M. , JONES D.
Published: April 2006

The use of sward height as a criterion for determining the time and extent of stocking‐rate changes on continuously grazed swards was investigated over a 2‐year period (1985–86) in a sheep production experiment. Swards of three contrasting perennial ryegrass (Lolium perenne L.) varieties were established with and without Aberystwyth S184 small‐leaved white clover (Trifolium repens L.) at an upland site (310–363 m) in mid‐Wales. From spring (late April) until weaning (mid‐July) the pastures were continuously stocked with Beulah Speckled Face ewes and Suffolk cross lambs. During this period sward heights of 4 ± 0.5 cm were obtained and maintained by regular adjustment of animal number on individual paddocks. Grass‐only swards received 160 and 200 kg N ha−1 and the grass clover swards were given 80 and 75 kg N ha−1 in 1985 and 1986 respectively.

Differences were observed between the treatments in sward height profiles over the season necessitating contrasting adjustments to stocking rates. Mean stocking rate necessary on early flowering Aurora (22 6 ewes ha−1) was respectively 27% and 17% higher than on late‐flowering Aberystwyth S23 and Meltra (tetraploid) ryegrasses; mean stocking rate on grass‐only swards was 19% higher than on the grass‐clover pastures.

It is concluded that sward height is a useful criterion on which to make adjustments to stocking rates to compare the potential performance of contrasting swards, under continuous grazing. The infrequent adjustments required to maintain a constant sward height, especially on the late flowering diploid perennial ryegrass variety on which many upland pastures are based, suggest that the criterion of sward height could be successfully employed on farms as an aid to efficient grazing management.
Effects of addition of cell wall degrading enzymes on the chemical composition and the in sacco degradation of grass silage
Authors: VAN VUUREN A. M. , BERGSMA K. , FROL‐KRAMER F. , VAN BEERS J. A. C.
Published: April 2006

Herbage (83%Lolium perenne and 17%Trifolium repens) was harvested 15,28 and 42 d after second cut, and ensiled in 1.5 liter preserving jars either directly, at 20% dry matter (DM), or wilted (30 and 45% DM). Each variant was ensiled with and without a commercial preparation of cell wall degrading enzymes and stored for 90 d at 30°C. Samples were then incubated in nylon bags in the rumens of three cannulated cows for 3, 6, 12, 24, 48 and 288 h to study the in sacco degradation of organic matter (OM), crude protein (CP), and (hemi) cellulose.

Addition of cell wall degrading enzymes significantly decreased cell wall content. The magnitude Of the decrease was influenced by stage of maturity and DM percentage. Maturity increased the DM content as well as decreasing the effect of enzymes on cell wall components. Lactic acid content increased and the pH value and ammonia (P < 0.05) decreased, indicating a greater extent of fermentation in the enzyme‐treated silages. Enzyme treatment had no effect on the content of digestible OM estimated by in vitro incubations.

The undegradable fractions of OM, CP and cell wall components were not significantly changed by the addition of enzymes. The results suggest that the cell wall degrading enzymes affected the insoluble, rumen‐degradable fractions, thereby increasing the instantly degradable fractions. Consequently, the calculated effective degradation of OM and CP in the enzyme‐treated silages was significantly (P < 0.05) higher than in the untreated silages.
Water‐soluble carbohydrates in perennial ryegrass breeding
Authors: HUMPHREYS M. O.
Published: April 2006

Water‐soluble carbohydrate (WSC) contents of the early heading perennial ryegrass cultivar Aurora and five late heading cultivars were assessed in samples from 1 m × 2 m plots cut eight times in 1983 and five times in 1984. Despite fluctuations due to effects of the environment and plant development, the ranking of the cultivars in terms of WSC generally remained constant. Aurora had the highest overall WSC content. Majestic and Aberystwyth S23 had the lowest while Perma, Melle and Ba 9795 were intermediate. In the same trial, the ranking of the F2 hybrids between the late heading cultivars and Aurora was also consistent with that obtained previously in F1 and F2 spaced plants. Melle F2 families had the highest WSC followed by Perma F2, Ba 9795 F2, S23 F2 and finally Majestic F2 families. This ranking also remained constant over a generation of intense selection for uniformity of heading date. It was concluded that WSC is a consistent and heritable trait in breeding perennial ryegrass. Aurora was a good resource for improving WSC but the turf‐type perennial ryegrass. Majestic, had a strong negative effect on WSC content in hybrid material.
Evaluation studies in the development of a commercial bacterial inoculant as an additive for grass silage
Authors: ANDERSON R. , GRACEY H. I. , KENNEDY S. J. , UNSWORTH E. F. , STEEN R. W. J.
Published: April 2006

Two 2×2 factorial experiments are described in which a bacterial inoculant being developed as a silage additive and containing a strain of Lacto‐bacillus plantarum (Ecosyl, ICI plc) was evaluated at two harvests (18 July and 30 September 1985) of two swards (perennial ryegrass and permanent pasture) in difficult ensiling conditions. On each occasion erbage was ensiled with and without inoculant using two 0·5–t capacity steel tower silos per treatment. The contents of the two replicate silos per treatment were combined for feeding to cross‐bred wethers in digestibility and metabolizable energy (ME) partition studies.

Overall, inoculated herbage declined in pH post‐harvest at a faster rate than control herbage (p<0·001) and three out of the four inoculated silages had lower pH, ammonia‐N, acetate and alcohol and higher residual soluble carbohydrate content (p<0·001) than control. Significantly higher digestibility of nutrients (P<0·05) was found in three of the inoculant‐treated silages and these also had significantly higher ME values than control (P<0·001), (10·58 and 8·77 MJ kg tol DM−1 for the treated and untreated silages respectively). The use of inoculant on herbage of only moderate ensiling potential therefore, produced significant improvements in fermentation quality and feeding value over control.
Evaluation studies in the development of a commercial bacterial inoculant as an additive for grass silage
Authors: KENNEDY S. J. , GRACEY H. I. , UNSWORTH E. F. , STEEN R. W. J. , ANDERSON R.
Published: April 2006

Two 2×3 factorial design experiments were conducted during 1985 to compare the effect of treating grass at ensiling with a silage inoculant (Imperial Chemical Industries plc) or formic acid with an untreated control, on fermentation, in‐silo losses, intake and performance of finishing cattle.

In experiment 1, three covered concrete‐walled silos were each filled with approximately 70 t of primary growth, unwilted herbage at each of two cutting dates, 20–21 May (early harvest) and 3 June 1985 (late harvest). In experiment 2, the above procedure was repeated for second regrowth grass with two cutting dates, 30 September‐1 October (early harvest) and 16–21 October 1985 (late harvest). The water‐soluble carbohydrate (WSC) contents of the herbage were low in both, being 130–160 and 121–137 g kg−1 DM for the first and second experiments respectively. In both experiments the formic acid‐treated silages attained lower temperatures than the inoculant‐treated and untreated silages. At both harvests in experiment 1 the pH, ammonia nitrogen (NH3N) and volatile fatty acid (VFA) contents of the inoculant‐treated and formic acid‐treated silages were significantly lower than those in the untreated silage. However, at the early harvest in experiment 2 the pH and NH3N contents of the inoculant‐treated silage were significantly higher than those in the two other silages. At the late harvest in experiment 2 the inoculant‐treated and the formic acid‐treated silages had significantly lower pH and VFA contents than the untreated silage.

After 126 d and 98 d storage periods in experiments 1 and 2 respectively, each of the six silages was offered to twelve 475 kg steers throughout a 70‐d period (experiment I) and a 63‐d period (experiment 2). In experiment 1 there were no significant effects of additive on silage DM intake, liveweight gain or carcass gain with the mean carcass gains being 0·49, 0·51 and 0·52±0·024 kg d−1 for the untreated, formic acid‐treated and inoculant‐treated silages respectively. In experiment 2 the mean silage DM intakes were 6·34, 7·33 and 6·60±0·151 kg d−1 and carcass gains were 0·27, 0·35 and 0·26±0·026 kg d−1 for the untreated, formic acid‐treated and inoculant‐treated silages respectively, formic acid treatment thus gave the most consistent results.
Factors influencing the effects of fungicide treatment on seedling emergence of perennial ryegrass (Lolium perenne)
Authors: LEWIS G. C.
Published: April 2006

Seeds of perennial ryegrass were sown by hand in micro‐plots. Six treatment factors were applied, in all combinations, totalling thirty‐two treatments. The factors were (a) firm vs light compaction of the seedbed, (b) 1 cm vs 2·5 cm sowing depth, (c) fertilizer applied to seedbed vs no fertilizer, (d) fungicides applied to the seed and seedbed vs no fungicide, (e) pesticide applied to seedbed vs no pesticide, and (f) soil kept moist after sowing vs soil kept dry after sowing. Overall, seedling emergence was increased by moist soil (18%), fungicides (16%) and by sowing at 1 cm depth (8%). In dry soil, fungicides increased emergence by 32% but had no effect in moist soil.

In other experiments, micro‐plots were sown at monthly intervals, from April to October. Seeds were either treated with benomyl + captan (3 g + 3 g a.i. (kg seed)−1) or not treated, and the plots were either covered to keep the soil dry, or uncovered. Seedling emergence on uncovered plots was increased significantly, by 16–28%, at the May, June, July and August sowings, when soil temperatures were at their highest and soil moisture contents at their lowest. On covered plots fungicides significantly increased emergence at the June sowing only, by 16%. The reasons for this anomaly are discussed.
Water‐soluble carbohydrates in perennial ryegrass breeding
Authors: HUMPHREYS M. O.
Published: April 2006

Perennial ryegrasses showing genetic differences in water‐soluble carbohydrate content (WSC) were assessed for dry matter digestibility (DMD), crude protein (CP) and dry matter production (DM) in both spaced plant and small plot trials. Among 100 accessions grown as spaced plants there appeared to be more genetic variation for WSC than for DMD or CP. In both spaced plants and plots, WSC was consistently positively correlated with DMD, negatively correlated with CP and showed little correlation with DM. Correlations between CP and DMD were rather inconsistent and some negative correlations were obtained between CP and DM, suggesting that environmental effects, particularly with regard to nitrogen availability, affected CP more than WSC content. It was concluded that there is considerable potential for using ryegrasses with high WSC contents to develop varieties with improved feeding value without sacrificing production.