摘要:

AbstractThis study sought to define the optimum defoliation interval forLolium perenne, with the maximum interval being determined by the onset of senescence, as reflected by the number of fully expanded leaves, and the minimum interval set by the replenishment of water‐soluble carbohydrates (WSCs).In a glasshouse set at 13°C/23°C night/day temperature and at a plant spacing of 94 m−2(3290 tillers m−2), the accumulation of dry matter against leaf number and days was exponential to the four‐leaf stage of the regrowth cycle. Senescence commenced at the 3·5‐leaf stage.WSCs in roots, stubble and leaf showed a very significant linear relationship with leaf number. Levels of WSCs in leaves were restored to predefoliation values by the one‐leaf stage, after which WSCs accumulated preferentially in the stubble, rising to 22% at the four‐leaf stage.Regrowth after 6 d was significantly greater for plants defoliated at the three‐leaf stage than at the one‐leaf stage, but this difference disappeared at the end of the regrowth cycle. This questions the importance of WSCs in determining the yield of ryegrass under normal rotational grazing management.Regrowth at 6 d was related positively to stubble WSCs (r2= 0·66) and to stubble

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1994.tb02013.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA comparison was made of the effect of season and maturity on thein situruminal breakdown and intestinal protein digestion in dairy cows between intensively N‐fertilized grass (whole sward) and moderately N‐fertilized ryegrass and clover from a mixed sward. From May to September 1990, eight consecutive cuts were made, representing alternate harvests of late and early swards. Limited effects of fertilizer‐N on chemical and ruminal degradation characteristics and intestinal digestion of grasses were observed. Clover had higher ash, crude protein (CP) and lignin and lower hemicellulose, cellulose and sugar contents than grass. Moreover, soluble fractions of organic matter (OM) and CP were higher, and rumen‐undegradable OM and CP fractions were lower. Soluble fractions of grasses and clover decreased and undegradable fractions increased during the season. More mature swards showed increased undegradable fractions. Degradation rates of OM and CP in clover were, respectively, higher than or similar to those of grass. Seasonal effects on degradation rates differed between grass and clover. Effectively rumendegradable (g kg−1DM) carbohydrates and CP, escaped protein and intestinal digestion of escaped protein were higher in clover than in grasses. Inclusion of clover in swards may result in higher post‐rumen protein supply. Supplementation of clover‐based diets is suggested to compensate for an increased loss of N

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1994.tb02014.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractResults from a series of five small‐scale plot experiments which simulated different strategies for lowering ammonia volatilization following slurry application to grassland are reported. Strategies studied were band spreading, shallow‐channel application, spike injection, rate of surface application and dilution. Volatilization was measured over the first 4 h following application with ventilated enclosures. Band spread slurry resulted in 0·4 of the volatilization that occurred from surface application of the same rate of slurry. The benefit of band spreading was shown to arise from higher application rates in the bands when compared with the same quantity of slurry spread over the surface. When surface‐spread slurry was applied to the same depth of slurry as in bands, the volatilization per unit volume of slurry was the same. Shallow‐channel application was more effective than band spreading and lowered volatilization per unit volume of slurry to<0·1 of that from surface‐spread slurry. Spike injection was equally effective as shallow‐channel application but, owing to perceived difficulties in machine design, construction and operation, was deemed impractical. Shallow‐channel application has potential, though further work is required to optimize centre‐to‐centre spacing of the channels. As the application rate of surface‐applied raw slurry increased, ammonia volatilization per unit volume of slurry applied decreased. Application at 50 m3ha−1resulted in 0·4 of the specific volatilization per unit volume of slurry that occurred at 6·3 m3ha−1. Within the dilution treatments, the amount of water added to the slurry was linearly and inversely related to volatilization. At a dilution of 0·9‐1·2:1 water: slurry the specific volatilization per unit volume of slurry was 0

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1994.tb02015.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractLucerne (Medicago sativaL.) sown at 2·8‐11·2 kg ha−1in spring was thinned in the autumn by digging plants from alternate 15‐ or 30‐cm lengths of row. Both thinning treatments decreased the subsequent year stand density by 34%. Yields the following year were reduced by 24 and 17% for the 15‐ and 30‐cm treatments respectively, and the next year by 10% for both treatments. Thinning effects were similar at all sowing rates. During the year following thinning, plants did not grow larger in response to the thinning. Thus, development of compensatory growth by lucerne plants following sudden stand thi

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1994.tb02016.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractIn two experiments (1990 and 1991) perennial ryegrass (cv. Talbot) pasture was subjected to six different management treatments by adjusting stock numbers to achieve set sward heights for set periods between turn‐out in early April and weaning in early July. The main objective of the experiments was to measure the effect of differences in sward management up to July on subsequent sward type, and the effect of sward type on the performance of weaned lambs between mid‐July and early October when all swards were grazed at a sward height of 7 cm. In Experiment 1 swards were grazed at 7 cm initially and then reduced to 3 cm at various dates and maintained at 3 cm until early July. In Experiment 2 swards were grazed initially at 7 cm, and this was reduced to 3 cm and then allowed to return to 7 cm at various dates up to early July.Grazing at a sward height of 7 cm up to weaning, in early July, gave mean twin lamb growth rates of 310 g d−1, while at a tower sward surface height of 3 cm lamb growth rate was reduced to 206 g d−1The density of seed heads produced from July was strongly influenced by earlier management. Grazing at 7 cm up to July gave a high density of seed heads (213m−2), and this reduced (126 m−2) by grazing to 3 cm. Seed heads were almost eliminated (17 m−2) by grazing at 7 cm until late June followed by grazing down to 3 cm in early July. Reducing sward surface height from 7 cm to 3 cm at an earlier date tended to increase the development of seed heads from early July. Where swards were grazed from 7 cm to 3 cm and then allowed to return to 7 cm, the later in the pre‐weaning period this took place the greater the reduction in seed head development. Greater seed head density was associated with a significant decrease in the nitrogen content of the herbage on offer in Experiment 2, but an increase in modified acid detergent (MAD) fibre content was not significant.Despite the differences in the sward type on offer, the effect on weaned lamb growth rate was small. Lamb liveweight gain during autumn was significantly reduced in Experiment 2 following earlier grazing at 7 cm compared with 3 cm, but liveweight gain differences in Experiment 1 were

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1994.tb02017.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractFrequency data from different‐sized plots are generally accepted as being incomparable. However, how basal frequency data are influenced by plant basal diameter is not well known. Computer simulations were used to determine the influences of grass plant basal diameter on basal frequency data. Basal frequency, basal area and density were estimated with simulated 5 × 10 cm and 20 × 50 cm rectangular plots. Simulated plants had basal diameters ranging from 1.9 to 12.7 cm.Basal diameter had a significant effect on the relationship between frequency and both basal area and density. As differences in plant size increase, the effect on basal frequency becomes larger and the likelihood of an ecologically important influence also increases. Thus, frequency data should not be used to compare relative abundance of species, unless corrections are made for differences in plant basal diameter among species. Additionally, frequency data should not be used to monitor change in abundance of a species through time, unless mean plant basal diameter can be assumed to remain relatively constant.Basal frequency data could be used to ‘signal’ when change has occurred. Then, other sampling methods must be used to determine the nature and direction of change or relative species abundance. For frequency data, the simplicity of collection may be offset by difficulty in interpr

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1994.tb02018.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractLeaf blades of perennial ryegrass (Lolium perenne) at five developmental stages, from unemerged to dead, were collected from cut swards grown under field conditions. Similarly, leaflets of white clover (Trifolium repens) at four developmental stages, from tightly folded to proximal to the youngest fully developed leaf, were collected. The leaves were analysed for N, P, K, Ca, Mg and Na.In perennial ryegrass, the concentration of N declined by about half and those of P and K declined by about two‐thirds, as leaves aged. By contrast, the concentration of Ca increased more than fivefold and that of Mg about twofold as leaves aged. The concentration of Na initially increased more than twofold but then declined as leaves died. In white clover the concentration of N declined by about 20% as leaves aged, while the concentrations of P and K declined by about 50%; the concentration of Ca increased about fivefold, that of Mg declined by about 15% and that of Na increased by about 15%.The application of N increased the concentrations of N and K in ryegrass leaf blades at all stages of development. The application of P increased the concentrations of P and Na in the leaves of both specie

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1994.tb02019.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractAn experiment was conducted to examine the relationships between sward surface height and the intake and liveweight gain of lactating female goats and their single kids and of 12‐month‐old castrated male goats continuously grazing grass pasture. Herbage intake was measured using then‐alkane marker technique. Goats grazed the experimental area from May to August at nominal sward heights of 3–4, 5–6, 7–8 and 9–10 cm. Sward heights achieved were variable but were consistently ranked in treatment order.The herbage intake of females [57‐140 g DM (kg LW0.75)−1d−1] and castrates [26‐88 g DM (kg LW0.75)−1d−1] increased linearly with sward height over the range 3.2‐11.0 cm. The liveweight change of females and castrates reflected the pattern of change in sward height.The herbage intake of kids [17‐41 g DM (kg LW0·75)−1d−1] was not related to sward height, but there was a consistent increase in liveweight gain with sward height from 98 to 129 g d−1. The herbage intake of kids did not increase with age with means of 25–29 g DM (kg LW0·75d−1for kids aged 9–17 weeks.There was evidence that all classes of goat selected

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1994.tb02020.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA randomized block design experiment involving thirty beef cattle (mean initial live weight 462 kg) was carried out to evaluate a bacterial inoculant based on a single strain ofLactobacillus plantarumas a silage additive and to provide further information in relation to its mode of action. Three herbages were harvested on 10 August 1989 using three double‐chop forage harvesters from the first regrowth of a perennial ryegrass sward which had received 170 kg N, 25 kg P2O5, and 42 kg K2O ha−1. They received either no additive (silage C), formic acid at 2·91 (t grass)−1(silage F) or the inoculant at 3·21 (t grass)−1(silage I). Mean dry‐matter (DM), water‐soluble carbohydrate and crude protein concentrations in the untreated herbages were 158g kg−1, 88 g (kg DM)−and 183g (kg DM)−1respectively. For silages C, F and I respectively, pH values were 4·01, 3·57 and 3·62; ammonia N concentrations 117, 55 and 77 g (kg total N)−1; and butyrate concentrations 2·18, 0·50 and l·24g (kg DM)−1. The silages were offeredad libitumand supplemented with 2·5 kg concentrates per head daily for 77 days. For treatments C, F and I, silage DM intakes were 6·59, 7·25 and 6·80 (s.e. 0·074)kg d−1; metabolizable energy (ME) intakes 86,99 and 94 (s.e. 0·8) MJ d−1; liveweight gains 0·90, 0·97 and 1·02(s.e.0·066) kg d−1; carcass gains 541,656 and 680 (s.e. 34·0) g d−1. Inoculant treatment increased DM (P<0·01), organic matter (P<0·01), crude fibre (P<0·05), neutral detergent fibre (NDF) (P<0·05) and energy (P<0·05) digestibilities, the digestible organic matter concentration (P<0·01) and the ME concentration (P<0·05) of the total diets. Additive treatment altered rumen fermentation patterns but had little effect on the rumen degradability of silage DM, modified acid detergent (MAD) fibre, NDF or hemicellulose. It is concluded that treatment with the inoculant improved silage fermentation and increased digestibility, had little effect on silage DM intake but significantly increased carcass gain to a level similar to that

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1994.tb02021.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe growth of grass and clover components in mixed swards on a site restored after opencast coal mining and an undisturbed control site were compared. Soil nitrogen supply was reduced at the restored site. This inhibited grass growth but was beneficial for the clover component.Growth at the restored site was also inhibited by a compacted subsoil, which reduced available soil water content and impeded access to available soil water. This inhibited crop production from the middle of the second silage crop onwards. In 1989 this was associated with the soil at the restored site reaching permanent wilting point at 40cm. In 1990 this effect was associated with the restored site soil reaching permanent wilting point at 70cm. These drought effects reduced clover growing point population and stolon mass. Grass tiller populations were unaffected.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1994.tb02022.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY