首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 40 毫秒
1.
Introgression of reproductive traits from the annual, profuse flowering, ball clover (Trifolium nigrescens Viv.) into white clover (Trifolium repens L.) is one breeding strategy to improve seed yields of T. repens that must be achieved without sacrificing agronomic performance and persistency under grazing. The yield and persistency of hybrids between white clover and T. nigrescens were compared under rotational sheep grazing over three harvest years. The hybrids included the backcross (BC) 2 and 3 generations produced using white clover as the recurrent parent. The large‐leaved T. repens variety Olwen, medium‐leaved varieties AberDai and Menna and the small‐leaved variety S184 were sown as controls. Hybrids and control varieties were sown with a perennial ryegrass companion; between April and the end of October in each harvest year the plots were rotationally grazed with sheep with clover and perennial ryegrass (DM) yield and the proportion of clover present measured over the growing season. The clover and total DM yields of the BC2 and BC3 were generally comparable with the small‐ and medium‐leaved varieties within the experiment and significantly greater than the yields of the large‐leaved variety Olwen. Throughout the 3 years of the experiment the BC2 maintained a clover content above 0·30 and comparable with the small‐leaved varieties, while the clover content of the BC3 was comparable with the small‐ and medium‐leaved varieties in the first and third harvest years. No significant difference in perennial ryegrass production was observed when grown with the backcrosses or the control varieties. Differences in stolon and growing‐point density were observed at the end of the experiment with the density of the BC2 and BC3 less than the small‐leaved variety S184 but, in common with the medium‐leaved varieties, greater than the large‐leaved variety Olwen. The implication of these results for the use of this material in future experiments and in the white clover breeding programme is discussed.  相似文献   

2.
Abstract The dry matter (DM) production of Trifolium repens, T. ambiguum and the backcross 1 (BC1) and backcross 2 (BC2) hybrids with T. repens as the recurrent parent were compared in mixtures with an intermediate heading variety of perennial ryegrass (Lolium perenne L.) under a cutting‐only management over 3 harvest years. Plots of parental legume species and backcross hybrids were established from small plantlets and oversown with the companion grass. In the first harvest year, the DM yield of clover in T. repens plots was greater than that in the BC2 plots and both greater than in the BC1 plots, whilst in the second and third harvest years differences between the DM yield of clover in the T. repens and the BC1 and BC2 hybrid plots were small. Similar results were obtained for the DM yield of total herbage. There were also differences in seasonal growth in the first harvest year, when yield of clover in T. repens plots was greater than in the BC1 and BC2 hybrid plots at early cuts but not at later cuts. Few differences in seasonal growth were observed between parental species and hybrids in subsequent harvest years. Comparison of above‐ and below‐ground biomass showed more DM in roots and rhizome of clover in the backcrosses than in the T. repens plots in the second harvest year but differences were less evident in the third harvest year. The clover in the backcross hybrid plots also had fewer stolon growing points per quadrat than the T. repens plots, but the BC2 had more than the BC1 plots. The exploitation of these hybrids in breeding programmes as a strategy to improve the persistence and drought tolerance of white clover is discussed and implications for forage production considered.  相似文献   

3.
Interspecific hybridization with the close relative Trifolium nigrescens Viv. (Ball clover) is a possible strategy to increase the seed yield potential of white clover (T. repens L.). Fertile F1 plants have been used as the basis for several generations of backcrossing using T. repens as the recurrent parent. Forage quality of the parental species and backcross hybrids when grown in mixtures with perennial ryegrass (Lolium perenne L.) was compared in field plots over three harvest years. The dry‐matter digestibility (DMD) and crude protein (CP) concentration of the legume fraction was greater than that of perennial ryegrass, but the water‐soluble carbohydrate (WSC) concentration of the legume components was lower than that of perennial ryegrass. Differences in forage quality between T. repens and the backcross hybrids were relatively small. The WSC concentration of the backcrosses was less than T. repens but the CP concentration was greater. Significant differences in the forage quality of the companion grass were observed when grown with the parental species and the hybrids; however, these differences were attributed to the plots with T. nigrescens and the F1 plants, where the clover content was low. Few differences in the forage quality of the grass were measured when grown with T. repens and the backcross hybrids. The impact of these results on the use of these hybrids in cultivar development programmes is discussed.  相似文献   

4.
Interspecific hybrids between white clover (Trifolium repens L.) and Caucasian clover (Trifolium ambiguum M. Bieb.) have been developed to introgress the rhizomatous growth habit into white clover, to increase persistence and drought tolerance. The forage quality of T. repens, T. ambiguum and the backcross 1 (BC1) and backcross 2 (BC2) hybrids and companion grass, when grown in mixtures with an intermediate perennial ryegrass (Lolium perenne L.) under a cutting‐only management, was measured. In vitro dry‐matter digestibility (DMD), water‐soluble carbohydrate (WSC) and crude protein (CP) concentrations of the legume and grass fractions were measured throughout the growing season over three harvest years. Trifolium repens had a lower WSC but a higher CP concentration than the perennial ryegrass companion in all harvest years and at all cuts. The legume fractions from the BC1 and BC2 hybrid plots had a higher WSC and a lower CP concentration but an in vitro DMD value comparable with white clover throughout the growing season and in each harvest year. The grass fractions from the mixtures with the backcross hybrids had a higher WSC and a lower CP concentration than the grass fraction from the T. repens plots, in all harvest years and throughout the growing season. No difference in in vitro DMD between parental species and backcross hybrids was observed. The implications of these results for the development of these hybrids and animal performance are discussed.  相似文献   

5.
In a field experiment carried out over 3 years, the nitrate content of herbage from perennial ryegrass (Lolium perenne) swards increased exponentially with nitrogen application rate, but herbage nitrate content appeared to reach potentially dangerous concentrations only when nitrogen application rates were greater than those needed to stimulate dry-matter production. Thus, on average over all the harvests, maximum yield could be obtained with annual application rates of 400 kg N ha–1 (six applications of 67 kg N ha–1) for perennial ryegrass and 300 kg N ha–1 (six applications of 50 kg N ha–1) for perennial ryegrass/white clover (Trifolium repens) swards, whereas the mean nitrate concentrations were 3340 and 2929 mg NO3 kg–1 dry matter (DM) respectively. Nitrate content, however, varied considerably from harvest to harvest, reaching maxima of 9345 mg NO3 kg–1 DM at 400 kg N ha–1 for perennial ryegrass and 6255 mg NO3 kg–1 DM at 300 kg N ha–1 for perennial ryegrass/white clover. The nitrate content of herbage from perennial ryegrass/white clover swards was always greater than that of perennial ryegrass swards receiving the same rate of nitrogen application, even though in the herbage from the mixed sward the nitrate content of white clover was usually less than half that of the perennial ryegrass component. The physical environment did not have a clearly interpretable effect on nitrate content, although herbage harvested in May had a much lower nitrate content than that harvested at any other time of the season. It was not possible to find a single multiple regression equation relating herbage nitrate content to nitrogen application and to other environmental variables that explained more than 60% of the variance in herbage nitrate, but it is suggested that, by reducing the later-season nitrogen applications from 67 to 50 and finally to 33 kg N ha–1 for perennial ryegrass and from 50 to 33 kg N ha–1 for perennial ryegrass/white clover, it would be possible to achieve over 90% of the maximum yield while reducing average nitrate content to <40% of that at maximum yield, with no samples containing more than 2300 mg NO3 kg –1 DM.  相似文献   

6.
Results are presented to show the effect of white clover (Trifolium repens) and of applied N on the hotanical composition of swards sown with perennial ryegrass (Lolium perernne), timothy (Phleum pratense), meadow fescue (Festuca pratensis) and mixtures of two and three of these species. White clover had a more favourahle effect on the growth of perennial ryegrass than on either timothy or meadow fescue both in terms of yield and in terms of tiller numbers. Tiller numbers of rough-stalked meadow grass (Poa trivialis) were increased and tiller numbers of Agrostis species were reduced by application of N and by inclusion of clover. Possible reasons for these effects are considered.  相似文献   

7.
Abstract Two experiments were carried out to evaluate the performance of blends of three white clover (Trifolium repens L.) varieties in comparison with the component varieties and three other varieties sown individually in a mixture with perennial ryegrass (Lolium perenne L.). The plots were grazed rotationally in Experiment 1 by cattle and sheep and in Experiment 2 by sheep alone. In both experiments, the blend was composed of three medium‐leaved varieties (AberDai, AberVantage and AberHerald), but with different relative contributions of the three varieties in the two experiments. Dry matter (DM) yields of white clover and perennial ryegrass were assessed in replicate plots for two years (1999 and 2000) after the establishment year. In Experiment 1, there was no significant difference between the DM yields of white clover or perennial ryegrass in either year. The decline in DM yield of white clover between years that was observed for some varieties was not found for the blend. In Experiment 2, significant differences were found in DM yields of white clover in both years. In 1999, AberDai had the highest DM yield. In 2000, AberHerald and AberVantage had the highest DM yields, and AberDai showed a decline in DM yield that was mirrored by the mean for all the white clover varieties. In both experiments, the blend did not show significantly higher DM yield than one or more of its components; indeed, in Experiment 2, it was significantly lower yielding than AberDai in 1999. However, where one component of the blend declined in DM yield between years, this was compensated for by an increase in the yield of another component. These preliminary findings suggest that the yield stability of blends may give them a potential role in agricultural practice.  相似文献   

8.
The effect of defoliation interval on growth patterns of contrasting perennial ryegrass (Lolium perenne)–white clover (Trifolium repens) mixtures was studied. The dynamics of increase in leaf area, light interception and dry-matter (DM) production were measured within successive regrowth periods. No N fertilizer was applied. During 1995 six mixtures were cut eight (F1) or six times (F2) at a stubble height of 5 cm. The stubble composition was stable throughout the growing season: after harvest about 50 g DM m?2 (with a white clover proportion of 0·52) was present with a leaf area index (LAI) of 0·5 (0·38 white clover). The percentage of intercepted radiation after cutting was 20–30% and increased during 3 weeks to about 95%. The relative growth rate of leaf area and DM was higher for white clover than for perennial ryegrass, with the proportion of clover in the LAI and DM increasing during each regrowth period. Mixtures with large-leaved white clover cv. Alice had a lower initial clover content after harvest, but a more rapid increase in clover LAI and DM than mixtures with the smaller leaved cvs Gwenda or Retor. Alice had the highest total and clover LAI and DM at harvest. Cutting frequency affected the change in white clover–perennial ryegrass ratio during regrowth. This was significantly higher in mixtures with Alice than in mixtures with Gwenda, but only under less frequent cutting (F2). In spring there was a mean white clover proportion of about 0·55 in the LAI and 0·45 in the total harvested DM. In summer the white clover proportion in the LAI and DM increased to 0·70–0·75. There was a decline during autumn, especially in F2 and in the mixtures with the small-leaved white clover cv. Gwenda and the medium-leaved cv. Retor. In contrast, grass DM and LAI declined from spring to summer. The decline in clover LAI in autumn was similar in Alice and Gwenda at frequent cutting (F1), but stronger in Gwenda in F2. Retor had the lowest clover specific leaf area (SLA). The SLA values of Alice and Gwenda were similar, SLA being similar between cutting treatments. No differences were found for leaf weight ratio (LWR) among the three white clover cultivars or between the grass cultivars, and LWR was not affected by cutting treatment. Defoliation interval had limited effects on the growth pattern and leaf characteristics of perennial ryegrass–white clover mixtures.  相似文献   

9.
Infestations of pastures by species, such as creeping bentgrass (Agrostis stolonifera), may compromise the white clover (Trifolium repens) content in perennial ryegrass (Lolium perenne) mixtures. However, the interactions between white clover and species other than perennial ryegrass are not well understood. Strategies to prevent creeping bentgrass infestations require an understanding of its interactions with white clover, as the exclusion of white clover from infested pastures could be the result of either direct interaction or niche‐differentiation in response to management. A methodology is presented which enables the segregation of the effects of direct interaction and niche‐differentiation, based on existing dry‐weight‐rank measurements of a number of experimental pastures, subjected to a range of management strategies. Only between the two management extremities, i.e. permanent cutting of silage and lax grazing for long periods, did niche‐differentiation occur between white clover and creeping bentgrass. The white clover content was enhanced under the cutting regime, whereas lax grazing for long periods stimulated the content of creeping bentgrass. White clover was actively excluded from creeping‐bentgrass‐dominated patches by direct interaction, whereas it showed a high compatibility with perennial ryegrass. This direct interaction presents challenges to the prevention of creeping bentgrass by management, as creeping bentgrass and white clover showed nearly identical requirements in terms of environmental conditions and grassland management.  相似文献   

10.
Six annual legumes were evaluated as components of cereal-grass-legume intercrops in two experiments at two sites differing in elevation by 789 m. Barley (Hordeum vulgare L.) and Westerwolds rye-grass (Lolium multiflorum Lam.) were seeded on all intercrop plots. Dry-matter (DM) yield, crude protein (CP) and organic matter digestibility (OMD) were measured. DM yield and N content were used to estimate legume N fixation. Experiment 1 was conducted at both sites. At the lower site, Persian clover (Trifolium resupinatum L.) and annual alfalfa (Medicago sativa L.) accounted for 70% of the DM yield in harvest 1 (July), increased CP and OMD, but did not affect intercrop yield. They increased harvest 2 (August/September) intercrop yield by 263% and CP concentration by 65 g kg?1 DM. They increased harvest 3 (October) yield by 275% and CP concentration by 78 g kg?1 DM. Inclusion of striate lespedeza (Lespedeza striata) did not affect intercrop yield or quality. Annual legumes failed to establish at the higher elevation site and therefore had no effect on DM yield or forage quality. In Experiment 2, in which the performance of Westerwolds ryegrass was also compared with that of Italian ryegrass, and conducted at the lower site only, Persian clover and berseem clover (T. alexandrinum L.) increased CP of all three of the year's harvests. These two species contributed 29% of the DM yield in the first harvest (July) but did not affect total intercrop yield. They increased harvest 2 (August) yield by 313%. Persian clover increased harvest 3 (October) yield by 318% and berseem clover increased harvest 3 yield by 405%. Barrel medic (Medicago truncatula) and snail medic (M. scutellata) contributed 29% of harvest 1 yield, and increased both DM yield and CP content. Medics did not regrow. Aubade Westerwolds ryegrass contributed a greater percentage of the DM yield than did Maris Ledger Italian ryegrass at harvests 1 and 2. Ryegrass type did not affect total DM yield but did affect forage quality; intercrops containing the Italian ryegrass had higher CP at harvest 2 and higher OMD at harvest 3 than those containing the Westerwolds ryegrass. Over both experiments, at the lower elevation site, stands with Persian clover, berseem clover or alfalfa produced 80% of the yield of barley-ryegrass receiving 250 kg N ha?1, and 165% of the yield of unfertilized barley-ryegrass. Berseem and Persian clover fixed about the same amount of N over the growing season; 188 kg N ha?1 in Experiment 1 and 134 kg N ha?1 in Experiment 2.  相似文献   

11.
Seven varieties or advanced breeding lines of white clover ( Trifolium repens L.), all of small leaf size, were grown separately in mixtures with perennial ryegrass ( Lolium perenne L.) in an experiment encompassing three harvest years. Harvestable dry-matter (DM) yield measurements were taken of these mixtures and of perennial ryegrass monocultures under two management regimes: cutting and continuous sheep grazing. Considerable differences were observed in the harvestable DM yields of white clover, perennial ryegrass and total yields of the mixtures between plots containing different white clover varieties. White clover yields were generally higher under cutting, and perennial ryegrass yields were higher under grazing. The difference between perennial ryegrass yield in monoculture and in mixture was variable. In the second harvest year, a significant interaction effect was seen between management and white clover variety for white clover yield but not for perennial ryegrass yield. The relationship between clover yield and grass yield differed between the two management regimes. Under cutting, a negative correlation was observed, indicative of competitive effects. However, under grazing, no such correlation was seen. Possible mechanisms underlying these outcomes are discussed.  相似文献   

12.
There is increasing interest in tall fescue (Festuca arundinacea Schreb.) in Western Europe and elsewhere, mainly because of its better drought resistance and yield potential compared with perennial ryegrass (Lolium perenne L.). Important drawbacks of tall fescue, compared with perennial ryegrass, are its lower digestibility and voluntary intake. Mixtures of both species might combine the advantages of each, and species interactions may eventually lead to transgressive overyielding. We compared the agronomic performance of tall fescue, perennial ryegrass and tall fescue–perennial ryegrass mixtures, as pure‐grass swards or in association with white clover (Trifolium repens L.). Tall fescue–perennial ryegrass mixtures differed in the proportion and ploidy of the perennial ryegrass component. Yield, feed quality and botanical composition were measured in the 3 years after the sowing year. We found significant effects of ploidy of the ryegrass variety and of the proportion of ryegrass in the initial seed mixture on the botanical composition of the swards. Nevertheless, all swards were dominated by tall fescue at the end of the experiment. No overyielding of the mixtures compared with that of single‐species swards was found, but feed quality was intermediate between that of the single‐species swards. Mixed swards had better drought resistance than L. perenne and higher feeding quality than F. arundinacea swards.  相似文献   

13.
A research programme was undertaken over two consecutive years with the purpose of studying the effect of herb–clover swards on lamb production performance year‐round. The focus of this study was on two consecutive late spring and early summer periods (2011, 2012). In each year, three sward treatments were compared on grazed paddocks with 40 lambs ha?1: (i) grass–clover mixture (perennial ryegrass [Lolium perenne L.] and white clover [Trifolium repens]); (ii) plantain–clover mixture (plantain [Plantago lanceolata], white clover and red clover [Trifolium pratense]); and (iii) chicory–plantain–clover mixture (plantain, chicory [Cichorium intybus L.] and white and red clovers). Lambs were weighed at 2‐week intervals, and carcass weights and GR tissue depth measurements were obtained at slaughter. In both years, lambs on treatments (ii) and (iii) had greater (P < 0·05) final live weight, liveweight gain, carcass weight, dressing‐out percentage and GR tissue depth measurements, and lower feed conversion ratio compared to lambs on treatment (i). Lamb production was similar in treatments (ii) and (iii) (P > 0·05) in each year. Therefore, during the late spring and early summer period, herb–clover mixture swards were found to be a superior option to perennial ryegrass–white clover for finishing lambs.  相似文献   

14.
Diversity of clovers in grass-clover swards may contribute to greater herbage yields and stability of yield. This possible effect was evaluated in an experiment carried out over three harvest years at two contrasting sites, differing in precipitation and soil composition, using mixed swards containing either one, two or three clover species sown together with timothy ( Phleum pratense L.) and meadow fescue ( Festuca pratensis L.). The clover species were red clover ( Trifolium pratense L.), white clover ( Trifolium repens L.) and alsike clover ( Trifolium hybridum L.) sown in various proportions in a total of ten treatments. All swards were fertilized with nitrogen with amounts that increased from year to year, and three harvests were taken in three consecutive years. There was a significant interaction between site and species mixture on total dry matter (DM) yields (range 27–32 tonnes ha−1) and DM yields of clovers (range 5–15 tonnes ha−1); red clover as a single species or in a mixture was superior at the dry site while multi-clover species mixtures were superior at the wet site. Alsike clover was the least productive species of clover. Stability of yield of clovers was generally higher by including white and red clover in the seed mixture but total DM yield was not.  相似文献   

15.
The selection by sheep (six Coopworth ewe hoggets, 44·3 ± 4·6 kg live weight) and goats (six Saanen/Anglo‐Nubian yearling males, 38·1 ± 3·8 kg live weight) for perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) and for sward height was measured in two experiments involving paired turves. Pairs of turves with herbage of differing height and of either the same or different plant species were offered. One sward (fixed height species, FHS) was always offered at 130 mm and the other (variable height species, VHS) at 130, 90 or 50 mm. Turves (450 mm × 220 mm) were cut to a soil depth of 100–150 mm from areas of perennial ryegrass and white clover regrown to the desired height after previously being cut to 30 mm. Each turf in a pair was weighed (±1 g) before and after grazing by penned animals maintained on a barley‐based pelleted diet. The number of prehending bites taken from each turf was recorded over a grazing period (128 ± 12 s). Bite mass, bite rate and intake rate were calculated. As the sward height of the VHS turf declined, an increasing proportion of the diet was selected from the 130 mm turf. When averaged over all height contrasts, both animal species selected a higher proportion (0·776 ± 0·026) of their diet from 130‐mm white clover than from 130‐mm perennial ryegrass (0·591 ± 0·018) turves. On average, goats selected a higher proportion (0·721 ± 0·022) of their dry‐matter (DM) intake from the 130‐mm turf than sheep (0·646 ± 0·019), but the effect was not consistent. In contrasts with perennial ryegrass as the VHS (and both perennial ryegrass and white clover as FHS), the proportion of the diet selected from the 130‐mm turf was very similar for both animal species. However, with white clover as the VHS (and both perennial ryegrass and white clover as FHS), goats selected a higher proportion of their intake from the 130‐mm turf to the extent that in the 130‐mm perennial ryegrass/50‐mm white clover contrast sheep showed as strong selection for 50‐mm white clover as goats did for 130‐mm perennial ryegrass. This lesser selection of goats for white clover as its height in a sward declines is likely to contribute to the higher white clover content observed in swards grazed by goats. Bite mass was greater on white clover (246 ± 5 mg DM bite–1) than on perennial ryegrass (173 ± 5 mg DM bite–1) and was greater for goats (255 ± 6 mg DM bite–1) than for sheep (195 ± 5 mg DM bite–1). Bite rate was greater on perennial ryegrass (45·9 ± 1·0 bites min–1) than on white clover (39·9 ± 1·0 bites min–1) and was greater for sheep (45·5 ± 1·1 bites min–1) than for goats (42·5 ± 1·1 bites min–1). Apparent intake rate by both sheep and goats was lower (mean, 5·0 ± 0·29 g DM min–1) on 130 mm perennial ryegrass/white clover than on 130 mm perennial ryegrass/perennial ryegrass (7·0 ± 0·27 g DM min–1), but was higher (9·62 ± 0·29 g DM min–1) on 130‐mm white clover/perennial ryegrass than on 130‐mm white clover/white clover (8·2 ± 0·29 g DM min–1) combinations.  相似文献   

16.
The n-alkane technique for estimating herbage intake and diet selection in dairy cows fed perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) herbages was evaluated. Pairs of animals were offered either 8, 10, 12 or 14 kg dry matter (DM) d?1 of herbage alone or with 2 kg DM d?1 of barley. Fresh herbage was cut daily from a perennial ryegrass/white clover sward and the appropriate amount was fed in four feeds during the day. Individual intakes and the white clover proportion of the diet were estimated during a 12-d period using the n-alkane technique. Animals were dosed twice daily with paper pellets containing dotriacontane (C32-alkane). Faecal grab samples were collected after the morning and afternoon milking. Three least-squares optimization methods were compared in calculating the white clover proportion in the diet; then, total DM intake was calculated. The different least-squares optimization methods gave similar predictions of the white clover content of the forage consumed. No significant (P < 0.05) effects of sampling routine, concentrate (barley) fed or interactions between the two were detected with respect to the difference between calculated and actual intake, the difference as a proportion of the total intake and estimated white clover content of the diet. The difference between the calculated and actual intake ranged from 139 to 366 g DM d ?1, which resulted in a proportional difference ranging from 0.004 to 0.02 depending on sampling routine. The actual white clover content of the herbage mixture fed was 0.42 ± 0.008, whereas the estimated white clover content ranged from 0.41 ± 0.006 to 0.43 ± 0.008. The results suggest that accurate herbage intake estimates can be achieved in dairy cows grazing perennial ryegrass/white clover swards if representative samples from herbage consumed can be collected.  相似文献   

17.
Mixed swards of white clover–grass mixtures in highly productive environments often fail to reach the minimum recommended annual clover proportion of about 0·30. This study assessed the effect on clover content and total dry matter (DM) yield of two spring N applications (0 and 45 kg N ha?1) and two distances between drilled grass‐rows (0·18 and 0·36 m) over 3 years for mown swards of white clover–Italian ryegrass (Trifolium repens–Lolium multiflorum) in binary mixtures in northern Italy. An additional aim was to determine the advantage of association of grass–clover compared with grass and clover monocultures. On average, N fertilization of mixtures resulted in almost 9% higher total yield (P < 0·01; mean response = 18·1 kg of total DM per kg of N) but decreased the clover proportion (0·250 vs. 0·312). Wider grass‐row spacing increased clover proportion (0·327 vs. 0·234; P < 0·01) with no reduction of total DM yield. N fertilization × grass‐row spacing interaction occurred only for clover content (P < 0·01). Without N fertilization, mixtures out‐yielded clover and grass pure stands. With N fertilization, at double rate to pure grass, yields from mixtures were greater than from clover and comparable to Italian ryegrass.  相似文献   

18.
Predicting species composition in mixed swards by near infrared reflectance spectroscopy (NIRS) can save labour in grassland research, provided equations are available. This study compares calibration strategies to predict species composition in swards with tall fescue (Festuca arundinacea), perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). The compared calibration strategies were based on either real or artificial samples. Real samples are samples taken from multispecies swards; the species composition is known by hand separating; after separating, the original samples are recomposed. Artificial samples are samples obtained by mixing single species grown in pure stands in known proportions. The performance of the equation based on real samples was significantly better than the performance of the equation based on artificial samples. We hypothesized that the weak performance of the equation based on artificial samples was due to a lack of environmental variation in the spectra of the artificial samples. The hypothesis was supported by the good performance of a novel calibration strategy based on the spectra of the artificial samples with added variation. According to the obtained results, a calibration strategy based on few but diverse calibration samples is discussed.  相似文献   

19.
This 6‐year experiment quantified the impacts of management factors on red clover yield, persistence, nutritive value and ensilability, and compared these with perennial ryegrass receiving inorganic N fertilizer. Within a randomized complete block design, field plots were used to evaluate a 2 (cultivar, Merviot and Ruttinova) × 2 (alone and with perennial ryegrass) × 2 (0 and 50 kg fertilizer N ha?1 in mid‐March) × 2 (harvest schedule) combination of the factors relating to red clover, and a 2 (harvest schedule) × 4 (0, 50, 100 and 150 kg N ha?1 for each cut) combination of the factors relating to perennial ryegrass. The early and late harvest schedules both involved four cuts per year, but commenced a fortnight apart. Red clover treatments averaged 14 906 kg dry matter (DM) ha?1 per year, whereas perennial ryegrass receiving 600 kg inorganic N fertilizer per year averaged 14 803 kg DM ha?1 per year. There was no yield decline evident across years despite a decline in the proportion of red clover. The early harvest schedule and sowing ryegrass with red clover increased the herbage yield and digestibility. March application of fertilizer N to red clover treatments reduced the annual yield. Early harvest schedule increased and both fertilizer N and sowing with ryegrass decreased the proportion of red clover. Sowing with ryegrass improved the indices of ensilability, but reduced the crude protein content. Both red clover cultivars had similar performance characteristics. A selected red clover‐based treatment, considered to exhibit superior overall production characteristics, outyielded N‐fertilized perennial ryegrass in mid‐season. However, it had poorer digestibility and ensilability indices.  相似文献   

20.
Four two-year field trials, arranged in randomised split-plots, were carried out in southern Sweden with the aim of determining whether reduced N fertiliser dose in winter wheat production with spring under-sown clover cover crops, with or without perennial ryegrass in the seed mixture, would increase the clover biomass and hence the benefits of the cover crops in terms of the effect on the wheat crop, on a subsequent barley crop and on the risk of N leaching. Four doses of nitrogen (0, 60, 120 or 180 kg N ha−1) constituted the main plots and six cover crop treatments the sub-plots. The cover crop treatments were red clover (Trifolium pratense L.), white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.) in pure stands and in mixtures. The winter wheat (Triticum aestivum L.) was harvested in August and the cover crops were ploughed under in November. The risk of N leaching was assessed in November by measuring the content of mineral N in the soil profile (0–30, 30–90 cm). In the following year, the residual effects of the cover crops were investigated in spring barley (Hordeum distichon L.) without additional N. Under-sowing of cover crops did not influence wheat yield, while reduced N fertiliser dose decreased yield and increased the clover content of the cover crops. When N was applied, the mixed cover crops were as effective in depleting soil mineral nitrogen as a pure ryegrass cover crop, while pure clover was less efficient. The clover content at wheat harvest as well as the amount of N incorporated with the cover crops had a positive correlation with barley yield. Spring barley in the unfertilised treatments yielded, on average, 1.9–2.4 Mg DM ha−1 more in treatments with clover cover crops than in the treatment without cover crops. However, this positive effect decreased as the N dose to the preceding wheat crop increased, particularly when the clover was mixed with grass.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号