摘要:

AbstractThis experiment was carried out to study the responses of sward components (particularly white clover,Trifolium repens) to grazing management in a natural sward dominated by smooth‐stalked meadowgrass (Poa pratensis) syn. Kentucky bluegrass. Treatments during two grazing seasons (1989–90) were: cattle grazing alone (C); cattle grazing followed by topping (CT); cattle grazing followed by sheep grazing (CS); and sheep grazing alone (S). Mean target pre‐ and post‐grazing herbage masses were 2200 and 1100 kg DM ha−1, estimated by single‐probe electronic capacitance meter. Sward component dynamics were monitored using turf dissections, marked white clover stolons, and ring‐toss white clover leaf counts. Component and sward data for the C, CT, CS and S treatments respectively, were: number of white clover leaves m−2, 1295, 1384, 1408, 900 (s.e. ± 108); number of leaves per growing point, 3·2, 3·4, 3·0, 2·8 (s.e. ± 0·2); herbage accumulation (t DM ha−1), 5·16, 5·02, 5·87, 8·28 (s.e. ±0 08); rejected herbage (% pasture area) 39·7, 7·7, 16·0, 0 (s.e. ± 75); and annual net herbage production (t DM ha−1) 3·39, 4·35, 4·99, 8·28 (s.e. ± 0.07). Swards grazed by sheep alone contained less white clover, but regrew quicker and produced more herbage than other treatments. Close topping or grazing by sheep following dairy cattle grazing decreased sward rejection by cattle. These treatments maintained more of the pasture in better condition for subsequent cattle grazing, resulting in greater net herbage production than where n

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02312.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThis experiment was carried out to improve understanding of sward and soil responses to cattle and/or sheep rotational grazing of low‐input (no N fertilizer), natural swards dominated by smooth‐stalked meadowgrass (Poa pratensis) syn. Kentucky bluegrass and based on white clover (Trifolium repens). Treatments during two grazing seasons (1989–90) were: cattle grazing alone (C); cattle grazing followed by topping (CT); cattle grazing followed by sheep grazing (CS); and sheep grazing alone (S), Mean target pre‐ and post‐grazing herbage masses were 2200 and 1100 kg dry matter (DM) ha−1. Plants in sheep‐grazed swards regrew more quickly and accumulated more herbage (8·28 compared to 5·35 t DM ha−1for cattle‐grazed swards, unadjusted for rejected area) than in other treatments. After 2 years, soil in sheep‐grazed areas contained 0·25% N, 5·7 kg available P ha−1, and 379 kg K ha−1, compared to an average of 0·19, 3·9, and 179 respectively for the same soil nutrients in cattle‐grazed treatments. Besides differences in manure distribution and sward rejection, differences in soil compaction among treatments also may have affected soil organisms and thus plant growth. After 2 years, soil bulk densities (g cc−1) were 1·37, 1·37, 1·27, and 1·12; soil penetrometer measurements (kg cm sec−1sec−1) to 20‐cm soil depth were 9·8, 9·3, 9·5, and 6·7; soil nematodes per 100 g of soil were: 5333, 8705, 2810, and 15208; soil rotifers per 100 g soil were: 288, 242, 715, and 33; and earthworms m−2(and their biomass (g m−2)) were 262 (205), 157 (162), 344 (409), and 294

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02313.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractSixteen landraces and twelve natural populations of Ladino white clover, and six large‐leaved control varieties, were assessed in Lodi (southern Lombardy, Italy) under a mowing regime for persistence, defined as ratio between clover dry matter (DM) yield over the last two years and clover DM yield over the five‐year crop cycle. Clover content in the sward was on average 35·2% in the fourth year and only 5·5% in the fifth year. Natural populations showed greater persistence and larger variation for this feature than landraces. Six natural populations were more persistent and higher yielding in the long‐term than the Italian variety Espanso and one of these populations performed better than the best of the control varieties, namely Lune de Mai and Olwen, atP<005. Persistence of the ecotypes was positively associated with stolon density and DM yield assessed in the third year, and to intemode length, whilst it was inversely related to seed yield and its components, especially the production of seed heads, so that hardly any ecotype could combine good persistence with high seed yield. This study discusses the potential use of these genetic resources in white clover breeding and suggests stolon density as a low‐cost, approximate indicator of long

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02314.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractAn experiment was designed to examine the changes in clover content of three mixed perennial ryegrass/white cover swards of differing initial clover contents subjected to different grazing height management regimes and their effect on lactation performance of 48 Friesian dairy cows and heifers. Two paddocks were established for each treatment and grazed on alternate days. Treatments T17 and Tl3 consisted of swards with initial clover contents of 0·17 and 0·13 of the dry matter (DM) mass, respectively, grazed to maintain compressed sward heights of 6 cm throughout the season. A third treatment, SI5, consisted of a sward with an initial clover content of 0·15 grazed to maintain a compressed sward height of 4·5 cm for the first 78 days of the grazing season (period 1). Throughout period 1, half the animals on each treatment each received 4 kg of a concentrate supplement daily, while the others remained unsupplemented. From days 79 to 90, the cattle on treatment S15 grazed a similar sward, while the compressed sward height of the S15 paddocks was allowed to increase to 6 cm before re introduction of the animals. The three swards were then grazed for a further 47 days (period 2) before the animals were housed and milk yield recorded for a further 63 days (period 3). While sward T17 showed little change in clover content over the first 29 days of grazing, remaining at just below 0·18 of DM mass, swards T13 and S15 showed a marked decline in clover content to 0·05 and 0·07 of DM mass respectively. However, by the end of period 1 the clover content of all three swards had increased markedly (0·25, 0·15 and 0·15 of DM mass respectively). By the end of period 2, clover proportions were slightly higher than initial values (0·19. 0·15 and 0·15 of DM mass for treatments T17, T13 and S15, respectively). Owing to the relatively small differences in clover content of swards TI7 and T13, there were no significant effects of these two treatments on milk yield or composition in any period. Supplementation had no effect on milk composition and had little effect on milk yield, except when sward height was maintained at 4·5 cm. There was no carryover effect of supplementation on milk yield or composition in p

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02315.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractData on the yield of lucerne for individual cuts and the total for three cuts from a uniformity trial were analysed. It was observed that CV% values decreased with the increase in plot size, both for each cut and for total yield. The decrease was considerable up to a plot size of 8 to 16 m2. The plot shape did not show any consistent effect. Increasing the size of block resulted in increased CV values, but block shape had no consistent effect. The CV values were highest for the first cut and lowest for the second cut. A relationship between the average CV% and plot size was found. However, this relationship, or its modified form Y= a.X1−b1. X2−b2taking into account the plot shape and considering the individual CV values, provide a good fit to the data for the cases where blocking was adopted. The coefficient of heterogeneity was less than 0·29, being lowest for first‐cut yields, followed by the total, the third cut and the second cut yields. This showed a high degree of positive correlation between yields of neighbouring plots. Blocking proved useful in increasing the efficiency of the experiment and it is suggested that block size may be kept at 8 or less plots per block. The relationship between average CV% and block size was of the from Y = a Xb. The present study suggests that, for field experiments with luceme, the plot size may be kept to a minimum that does not exceed 8 to 12 m2, in blocks of eight to nine plots with the shapes of plots and blocks being nearly square. Calculating the efficiencies of confounded factorial design and incomplete block design revealed that block size may be kept to a minimum. The recovery of interblock information was found useful and balancing may be attempted, but only, if nec

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02316.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThis experiment evaluated a bacterial inoculant based on a single strain ofLactobacillus plantarumas a silage additive. Three silages were harvested on 8 September 1989 from the second regrowth of a perennial ryegrass sward, which had received 167 kg N, 28 kg P2O5and 45 kg K2O ha−1. Mean dry matter (DM) and water soluble carbohydrate concentrations of the herbages at ensiling were 148 g kg−1and 78 g.(kg DM)−1respectively. Herbages were treated with either no additive (C), formic acid (3·0 1 t−1) (F) or the inoculant (3·0 1 t−1) (I) and were ensiled in three 80‐t capacity silos. For silages C, F and I respectively, pH values were 4·70, 3·77 and 4·47, ammonia‐N concentrations were 192, 111 and 182 g (kg total N)−1and butyrate concentrations were 6·8, 1·8 and 7·1 g (kg DM)−1. The silages were offeredad libitumand supplemented with 2·0 kg concentrates per head daily to thirty‐six heifers (mean initial live weight 442 kg). For silages C, F and I, silage DM intakes were 12·7, 14·4 and 14·1 (s.e. 0·42) g (kg live weight)−1, metabolizable energy intakes were 155, 166 and 172 (s.e. 5·1) kJ (kg live weight)−1, and estimated carcass gains were 456, 519 and 518 (s.e. 28·1) g d−1respectively. A further 18 similar cattle were used in studies on the digestibility of the silages, and rumen degradation of each was estimated with three mature cattle. Inoculant treatment significantly increased crude fibre (P<0·01), neutral detergent fibre (P<0·01), modified acid detergent fibre (P<0·01), hemicellulose (P<0·05) and N digestibilities (P<0·05) and tended to increase N retention from the total diet. It is concluded that although treatment of herbage that was difficult to ensile with the inoculant did not improve silage fermentation, it significantly increased digestibility, especially of the fibre fractions, and silage DM intake and tended to increase animal performance to levels similar to those achieved with a well preserved formic acid‐treated silage. Increases in silage DM and metabolizable energy intakes are likely to have been attributable to the effects of the inoculant on d

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02317.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractPerennial ryegrass/white clover (Lolium perennel Trifolium repens) pastures of three white clover varieties were compared at UK lowland (Plas Gogerddan, PG) and upland (Bronydd Mawr, BM) sites over three harvest years (1989–91) under continuous variable stocking (ewes and lambs until weaning and lambs thereafter). Mean annual lamb output from small‐leaved S 184 (1179 kg ha−1) was 29% greater than that from prostrate small‐leaved AberEndura at PG with medium‐leaved Huia also giving 19% more output than AberEndura. At BM, output from S 184 (863 kg ha−1) was 19 and 14% greater than that from AberEndura and Huia respectively. The differences in lamb output between the small‐leaved varieties owed to a combined effect of higher individual lamb growth rates and greater stock‐carrying capacity, both of which were more pronounced in the post‐weaning period. The higher output from S 184 relative to Huia at BM was attributed to higher stocking rate, particularly after weaning. Clover productivity and persistence were also studied under three cutting‐only managements at PG. Performance under a treatment cut at 2–3 cm every 10 d (T1), which is synonymous with assessment of persistence in UK National List testing, was poor with clover growing point number of only 498 m−2compared with 4906 m−2on the grazed sward in autumn 1991. Although productivity and clover content under T3 (cut at 3–4 cm every 42 d — similar to National List yield regime) gave the same varietal ranking as lamb production, there was an under‐estimation of the small‐leaved varieties, particularly AberEndura, relative to Huia. An intermediate treatment (T2), cut at 3–4 cm every 21 d, also over‐estimated the performance of the medium‐leaved variety. Herbage data from ground level sampling every 21 d using exclosure cages on the grazed swards were also poorly related to lamb performance. These results highlight the effect of clover variety on lamb production, which appeared to be independent of leaf size, and also confirm the existing problems associated with assessment of white

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02318.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractIntraspecific competition inLolium perennewas studied using a replacement series of a short‐leaved and a long‐leaved genotype that was managed under different cutting frequencies and nitrogen supplies. Leaf length, tiller density and yield were recorded 6 months after sowing. Since the two competitors were labelled at thePG1/2locus, it was possible to identify unambiguously the origin of tillers in the mixtures and to estimate the average length of lamina of each genotype. The difference in leaf length between the two competitors was maintained under particular types of management and generated contrasting competitive abilities leading to evolution of the genotypic composition of the mixtures. Thus, under infrequent cutting, competition for light resulted in the domination of the long‐leaved genotype and in a concomitant intragenotypic selection for leaf length. Supplying nitrogen fertilizer emphasized the phenotypic plasticity of the genotypes, particularly of the dominated one. Frequent cutting reduced competition for light and the change towards the short‐leaved genotype was far less rapid. The yielding and competitive abilities of ryegrass genotypes and the implications for breeding are briefly di

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02319.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractPure perennial ryegrass or perennial ryegrass/white clover mixtures (70:30 and 40:60 on a fresh‐matter basis) were ensiled in laboratory silos either untreated or alter treatment with freshly cultured Lactobacillus (Lb.)plantarunor freshly culturedLb. plantarumplusLactococcus (Lc.) lactis.freeze‐driedLb. plantarumor freeze‐driedLb. Plantarumplus sodium formate, sodium formate or formic acid. The effect of these additives on silage fermentation characteristics and quality of the resultant silages was examined. There were significant interactions between treatments and herbages for all silage quality parameters measured, except for acetic acid concentration. The influence of additives on the final pH of all silages was small but statistically significant. Lactic acid concentration was not directly related to herbage mixture, overall mean values ranging from 118 to 120 ± 1.5 g kg−1dry matter (DM), but wider variation was seen between treatments for individual herbage mixtures. Acetic acid concentrations were significantly (P<0·001) affected by herbage mixture ensiled, increasing linearly as clover content increased from zero to 60%. Untreated control and formic acid‐treated silages contained significantly (p<0·001) higher acetic acid concentrations than those treated with other additives. Silage ammonia N concentrations were significantly (p<0 001) influenced by herbage mixture. Lowest ammonia N concentrations (<50 g kg−1DM) were observed in silages that had been treated with formic acid, freshly culturedLb. plantarumorLb. plantarumplusLc. lactis.The fraction 1 leaf protein (FILP) contents of silages were significantly (P<0·001) affected by both treatment and herbage mixture, with consistently and significantly higher values found in freshly cultured inoculant‐treated silages. A poor correlation (r2= 0·12) existed between ammonia N and FILP in all silages. The inclusion of up to 60% white clover in the ensiled herbage did not adversely affect final silage quality. However, additive treatment markedly influenced the residual FILP content of silages, those treated with freshly cultured inoculants having

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02320.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractWhite clover (Trifolium repens) grows both horizontally, via the stolon, and vertically, via the petiole, through its environment. Comparing the effects of clear and opaque paint allowed the localization of two photoperceptive sites. Stolon growth (horizontal) was altered by the radiation environmental the node, and petiole growth (vertical) by radiation perceived at the petiole tip. Photoperception these two sites provides a mechanism by which the plant can direct its growth to exploit its environment maximally.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02321.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY