摘要:

AbstractThe ingress ofPoa annuainto established swards of perennial ryegrass was recorded in four experiments aimed at determining whether ingress was due toP. annuaaggression or to a decrease in ryegrass vigour. Emphasis was placed on severity of defoliation, effect of bare spaces and the time of year most favourable to colonization.In Experiment 1,P. annuaingress was greatest in the autumn, especially where ryegrass had been sown in rows rather than broadcast sown. In Experiment 2, seedlings ofP. annuaonly established successfully in mature ryegrass swards that had been defoliated at intervals of two weeks. Experiment 3 showed that ingress was inversely related to the vigour of the ryegrass cultivar, being particularly high on frequently defoliated plots. In Experiment 4, which involved a study of the colonization of poached areas, more seedlings established in quadrats surrounded byP. annua‐dominant pasture compared with patches surrounded by perennial ryegrass.It is concluded thatP. annuais not an aggressive species; it colonizes only open ryegrass swards that have become weakened by intensive managemen

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01699.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractWhite clover swards were grown in a freely ventilated glasshouse during August and September 1979. The uninterrupted growth of these swards, which were grown in Perlite with either nitrate or biologically fixed nitrogen, was studied from 5 weeks after sowing until peak dry weights of the live sward components occurred. The dry weight of leaf laminae, petioles, stolons, roots, nodules and dead material was determined weekly together with live leaf numbers and leaf lamina area. The pattern of dry matter accumulation of the yield components of the swards (live leaf laminae plus petioles) was characterized by an initial period of more or less exponential growth up to 6 weeks from sowing dominated by leaf lamina development. This was followed by a linear phase, when petiole weight increased rapidly and a final slowing down period terminated by peak yields of live DM 12 weeks after sowing.The weight of stolons, roots and nodules increased slowly during the period dominated by leaf lamina growth compared with the rapid increase thereafter, which resulted in a two‐ to three‐fold increase in the weight of stolons, roots and nodules by the time the weights peaked. It is assumed that after the leaf area index of the sward had reached a plateau there was a limit to the assimilate supply to the sward components at a stage when they were all apparently competing for photosynthates. There was a progressive slowing down in the rate of dry matter acc

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01700.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractSmall plots of permanent pasture containing 50%Agrostis capillaris‐Festuca rubrawere defoliated frequently or infrequently during the growing seasons in 1978–80 and fertilized with 133, 125 and 125 kg N, P2O5and K2O respectively ha−1a−1or not fertilized during 1978–81. Yields of herbage were assessed during 1979–80 and botanical composition assessed on three occasions in 1978, once in April 1979 and once in 1982.Fertilizer application increased annual dry matter (DM) harvested from frequently cut plots by 40%, 53% and 65% in 1978, 1979 and 1980 respectively, and on infrequently cut plots it doubled hay DM harvested in 1978 and increased total DM harvested by 126% and 186% in 1979 and 1980 respectively. Infrequent cutting and fertilizer both decreased the proportion ofA. capillarisbut only fertilizer decreased the proportion ofF. rubra.Fertilizer greatly increased the proportion ofHolcus lanatusespecially where plots had been cut frequently and ofAlopecurus pratensiswhere they had been cut infrequently. It decreased the proportion ofLuzula campestris.Infrequent cutting, especially with fertilizer, discouragedCerastium fontanumssp.glabrescensandTrifolium repensbut encouragedRu

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01701.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractData are presented for the fourth (1979) and fifth (1980) harvest years of a trial in which four levels of N fertilizer (0, 30, 60 and 90 kg N ha−1) were applied each spring to swards with grass (perennial ryegrass cv. Barlenna) and each one of four cultivars of while clover (Blanca, Sabeda, Olwen and S100) or grass alone. Results from the first three years have been published.Dry matter (DM) harvested dropped from the fourth to fifth years over all swards by 1 −5 to 2 0 t ha−1but response to N was maintained (17.4 and 24.4 kg DM (kgN)−lin response to 90 kg N ha−1in 1979 and 1980 respectively) despite reductions in summer yields relative to unfertilized swards. Blanca swards produced significantly less DM harvested than all other cultivars in 1979 and all cultivars in 1980 except for Olwen. Clover DM harvested continued to fall from 1977, the mean for the unfertilized treatment in 1980 being 55% of that in 1979. Up to 1980 Sabeda swards produced more clover DM harvested than Blanca swards. Linear regressions between annual clover content at zero N and at each spring N level for each sward type over 5 harvest years were very highly significant. It is concluded that all cultivars used responded similarly to spring N. Further work to develop a method for predicting the effect of spring N on clover content of given swards is

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01702.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractMasham ewes, stocked at 20 ewes ha−1, reared twins at pasture in 1979 and 1980 and were rotationally grazed around six paddocks. There were three lengths of grazing cycle (18, 30 or 42 d) and the ewes at pasture were either offered silagead libitum(S) for 8 weeks of lactation or they were not supplemented with silage (N). By feeding silage, S ewes and lambs moved into greater herbage masses (3735 u. 3390 kg organic matter (OM) ha−1), but there was little effect on net herbage accumulation (10.5v.10.0 t OM ha−1) and herbage intakes per ewe were similar (2.31v. 2.27 kg OM d−1) over the 7‐month grazing season. During the period of silage supplementation, total intake was 19% higher for S than N ewes, lamb growth rates were slightly higher (280v. 273 g d−1) and the ewes lost less weight (−78v−96 g d−1).For 18‐, 30‐ and 42‐d grazing cycles respectively the herbage masses before grazing were 2825, 3620 and 4240 kg OM ha−1; net herbage accumulations were 9.8, 10.4 and 10.6 t OM ha−1; mean daily herbage intakes by each unit (ewe+lambs) were 2.22, 2.35 and 2.30 kg OM and lamb growth rates from birth to weaning at 20 weeks were 205, 204 and 204 g d−1.Frequent grazing of relatively light herbage masses or infrequent defoliation of heavier herbage masses made little difference to sward or animal performance. It is concluded that, at this stocking rate, different grazing cycles of 18, 30 or 42 d do not affect the

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01703.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractData on sheep live weights, herbage standing crop and herbage quality are presented from a 3‐year grazing management study comparing set stocking, four‐paddock rotational grazing and four‐paddock forward rotational grazing systems. In both rotational grazing and forward rotational grazing systems, sheep were sequentially moved from one paddock to the next every 5 days. Lambs were weaned at 12–15 weeks of age in the forward rotationally grazed system and from then on grazed one paddock ahead of the ewes. Herbage mass was consistently greater on the rotationally grazed system than on the set‐stocked system, averaging 38.4% more herbage in 1978. 32.8% more in 1979 and 52.7% more in 1980. No differences were observed in ewe live weights at the end of the grazing year between the rotationally grazed and the set stocked systems. Live weights of rotationally grazed lambs were superior to set‐stocked lambs only when herbage allowance was low; otherwise no difference existed between these two systems. The forward rotationally grazed lambs generally had lower liveweights than did the rotationally grazed lambs, perhaps due to wea

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01704.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractExperiments were carried out on seven sites in Fermanagh to investigate the yield loss caused by leatherjackets in grassland. Populations on the sites ranged from 65,000 to 865,000 ha−1and significant damage was recorded from all sites except the least populated. Greater yield increases were obtained by controlling leatherjackets in September when compared with control in March. Regression models were fitted and it was found that 125,000 leatherjackets ha−1in March caused a yield loss of 50 kg herbage dry matter (DM) ha−1by mid‐May. Based on these figures the average yield loss to leatherjackets in Northern Ireland, from 1965 to 1982, was 208 kg DM ha−1. Controlling leatherjackets in September, rather than March, increased the potential avoidable yield loss by a factor of 2.72. The average yield loss at first silage cut is therefore 566 kg DM ha−1. On average, 100,000 ha grassland in Northern Ireland may be suffering an annual loss of 1t herb

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01705.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractComparisons between some aspects of grazing and ruminating behaviour by sheep recorded automatically and by manual observation are reported.Behaviour was recorded manually and automatically on four swards with surface heights of 3, 6, 9 and 12 cm. The automatic recording method gave significantly higher biting rates (78v67 ± 2·4 bites min−1) than manual recording. Possible reasons for these differences are discussed. For recordings during ruminating there was no significant difference between the two recording methods.As sward surface height increased biting rate decreased by 4·6 (± 0.65) and 2·9 (± 0·87) bites min−1cm−1, and masticating rate increased by 4·5 (± 1·13) and 3·7 (± 0·95) chews min−1cm−1for the manual and automatic recording methods respectively.It is concluded that the automatic recording system gives higher rates for jaw movements during grazing than manual recording but there is little difference between the two methods for activities reco

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01706.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractRecords of grassland productivity have been used for 93 farms in 1975–76 (a dry year) and 117 farms in 1977–78 (a wetter year). The samples were selected to contrast well‐drained and poorly/ badly drained farms and were further subdivided into dairy and beef. The number of farms in each of the four subsamples for each year was between 19 and 32. In addition the number of days on which the soil was at meteorological field capacity (field capacity days) on each farm was calculated.The mean utilized metabolizable energy (UME) output within the dairy sample was 45 GJ ha−1on both well‐drained and poorly/badly drained farms. Within the beef sample the output was 41 GJ ha−1on well‐drained farms and 37 GJ ha−1on the poorly/badly drained farms.The correlation between fertilizer N and UME output was stronger on well‐drained farms than on the poorly/badly drained farms in the wetter year (r = 0.69v.0.16 on dairy farms; r = 0.56v.− 0.12 on beef farms). In the drier year the converse was found (r=0.15v. 0.49 on dairy farms; 0.13v.0.44 on beef farms). The effect of field capacity days on output was inconsistent; only within the dairy sample in the wetter year did increased wetness appear to reduce output.It is suggested that soil wetness may have only a small effect on utilized output from grassland on a whole‐farm basis because (i) most farms have at least some well‐drained land, (ii) much of the utilization damage occurs in relatively short periods in spring and autumn and (iii) despite having utilization problems, badly drained land is capable of growing la

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01707.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe utilization of sown and indigenous plant species was studied in three experiments in which plots were stocked with similar live weights of sheep and goats. In the first experiment the animals grazed plots containing 0–5 ha of rush (Juncus effusus)‐ infested reseeded pasture and 0–5 ha of unimproved blanket bog. The second and third experiments took place on old rush‐infested improved pasture; in one experiment two levels of herbage mass of grass were provided while in the other the rushes were cut in spring or remained uncut.The goats grazed the rushes readily in all three experiments. Reduction in herbage mass of grass increased utilization of rushes by goats although these animals still grazed rushes when grass supply was plentiful. Sheep scarcely grazedJ. effususeven when hard‐pressed by shortage of grass. Both sheep and goats grazedJ. acutiflorus.In Experiment I sheep utilized reseeded pasture more heavily than did goats. Sheep grazed similar proportions of the leaves of grass and clover while goats grazed a lower proportion of clover leaves as compared with grass. Among the grasses sheep discriminated in favour ofLolium perennewhereas goats did not. On the blanket bog vegetation,Eriophorum vaginatumandCalluna vulgariswere grazed both earlier in the season and more heavily by goats than by sheep.The relationships between sward structure and grazing height in accounting for differences in species selection by sheep and goats are briefly discussed. The possibility of using goals to control coarse weeds in hill pasture and for strategic grazing to manipulate floristic composition is

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01708.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY