摘要:

AbstractThe present study was aimed at testing the hypothesis that a dense maize stand (320–720·203plants ha‐1) will produce more dry matter of acceptable quality than a stand sown at the density generally advocated (105plants ha‐1). It was also aimed at proving that grain is not essential in order to obtain a high yield of good‐quality forage maize.It was found that dry matter yield increased with density, especially at the early stages of growth. When ear‐formation was depressed by increasing plant density, the resulting reduction of ear yield and its quality due to the absence of ear was partly compensated for by the increased yield and quality o

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1981.tb01551.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractGrowth measurements were made onLolium perenne‐dominant vegetative swards during 4‐week regrowth periods following grazing or cutting.In the grazing study, the ryegrass (Lolium perenne) swards were grazed for 12‐d periods with stock numbers set according to initial herbage allowances per animal of 16, 32 and 64 kg organic matter per sheep. One area was grazed in summer and another area in the autumn.In the cutting experiment four ryegrass swards growing in boxes were prepared by cutting to either 2 or 6 cm at either 14‐ or 28‐d intervals. The swards were cut back in autumn to 2 or 6 cm. During the regrowth period half the boxes were retained in full light and half shaded to 48% of incident light.Herbage weight, rates of leaf extension, senescence, leaf appearance and tillering, water soluble carbohydrate reserve levels in tiller bases and, in the cutting experiment, sheath tube lengths and lamina lengths of leaves which had grown through the sheath tube were measured at intervals during the regrowth period.Final herbage weights reflected management history but net herbage accumulation over the four‐week regrowth period, though affected by season, pretreatment and light level, was similar on swards subjected to different grazing or cutting treatments.This result was partially explained by changes in the balance between growth and senescence per tiller as herbage weight increased with time during regrowth, and partially by the reduced production per tiller in harder‐grazed swards being offset by a rapid increase in tiller numbers.There was a positive curvilinear relationship between lamina length and the length of the sheath tubes through which the laminae emerged.Carbohydrate reserve levels declined rapidly after grazing or cutting, the extent of the decline being related lo the severity of the defoliation. Recovery commenced after four days in summer and was complete within 3 weeks but reserve levels remained low in plants grazed or cut in autumn.The need is discussed for more detailed descriptions of sward states in management studies and for more information on component processes of growth, the factors affecting them and how these interact with different kinds of manag

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1981.tb01552.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractIn an experiment of four years duration, the competitive relationships between three cultivars of white clover (Trifolium repensL.) and ten cultivars of perennial ryegrass (Lolium perenneL.) were studied under a N fertilizer regime of 200–240 kg ha‐1a‐1. The clover cultivars were selected to embrace the various leaf sizes from medium large to small and the ryegrasses included early, mid‐season and late cultivars with a known range of persistence.During the experiment there was a progressive decline in the contribution of clover, though the different characteristics of each of the clover and ryegrass cultivars produced substantial deviations from the average trend. The clover cultivar Kersey was significantly more aggressive towards the companion grass cultivars than either S100 or S184. It produced consistently greater clover contribution to total yield than the other two cultivars and significantly depressed the yields of some of the companion grass cultivars. There was evidence that compatibility of the ryegrass cultivars with clover was inversely related to persistence; the non‐persistent ryegrass cultivars S321 and Presto consistently produced lower grass yields than the more persistent cultivars and consequently permitted greater clover contribution. In the second and third years yield substitution effects between clover and grass components substantially reduced differences in the total grass‐clover yield.The interactions revealed in the experiment showed that both ryegrass and clover cultivars have the potential to influence each other when in association although, with minor exceptions, total annual yields were similar for all grass and clover mixtures at the moderately high level o

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1981.tb01553.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractCruciferous catch crops are an important source of forage, particularly in sheep systems, but due to their late sowing date, commonly July or early August, soil moisture is often a limiting factor in crop establishment and subsequent growth, causing wide variations in yield from year to year. Crops of stubble turnip (Brassica campestrisssp.rapifera), forage rape (B. napusssp.biennis) and fodder radish (Raphanus sativus) were grown at Hurley between 1969 and 1977. Fodder radish was the most variable in dry matter (DM) yield, while stubble turnip was the most stable. Both DM yields andin vitrodigestibilities rose during the autumn, reaching a maximum in mid‐December for stubble turnip and forage rape, and in mid to late November for fodder radish. Yield and digestibility subsequently declined. The N concentrations of the forages exhibited a contrary trend, reaching minimum values at about the time of the highest DM yields. The gradual changes in crop quality suggest that the crops are well suited to grazing utilization, in which management is simplified if crop quality shows little variatio

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1981.tb01554.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractTwenty‐four Hereford × Friesian cows and their South Devon cross calves were allocated to three herbage allowances allotted daily for three periods of 8 weeks in a Latin square design. The daily allowances were 17, 34 and 51 g dry matter per kg cow plus calf live weight. Milk production was depressed by 0·2 and 1·2 kg d‐1at the medium and low allowances. The corresponding falls in liveweight gain were for cows 0·26 and 0·25, and for calves 0·27 and 0·24 kg d‐1. Residual sward height after grazing gave a better indication of the animals' reaction to sward conditions and the management imposed than actual herbage allowance. The quantity per unit area and the composition of material present were important factors influencing intake. Calves were unable to compete with their dams to maintain herbage intake at the lower allowances and therefore are likely to benefit from additional feeding or creep grazing when residual sward height falls below 6cm for periods in excess

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1981.tb01555.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractGroups of eight Hereford × Friesian cows and their South Devon cross calves were set stocked over a 24‐week grazing season at 3·23 (low), 3·21 (medium) or 4·24 (high) cows ha‐1together with their calves. For the first 8 weeks only two‐thirds of the total area was grazed. Increasing the stocking rate from low to medium reduced daily milk yield and cow and calf liveweight gains by 1·2, 0·24 and 0·29 kg d‐1respectively, and from medium to high by 1·2, 0·24 and 0·23 kg d‐1. The main sward factor influencing faecal output and herbage intake was the quantity of organic matter on the pastures but the digestibility of the herbage selected also exerted a significant effect on the intake of cows. Major depressions in the herbage intake of cows occurred once the average sward height fell below 7 cm. Output of calf live weight was 628, 658 and 743 kg ha‐1for the 3 stocking rates from low to high, and for cows 246, 179 and 30 kg ha‐1. It was concluded that decisions on pasture management should be taken in relation to the cow rather than the cal

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1981.tb01556.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe effect of artificial dehydration and processing of red clover on nutrient digestion and absorption has been studied with sheep. A total of three diets were fed, each at an intake of 900 g DM d‐1; comprising frozen (to represent fresh control), wafered and pelleted red clover.Dehydration caused small depressions in energy and N digestibility. Grinding and pelleting had no further effect, although both treatments reduced the amount of energy digestion occurring in the rumen, frozen 63, dried 60, pelleted 48 MJ per 100 MJ digestible energy. Digestion of energy in the caecum and colon was increased on both dried diets, and in the small intestine on the pelleted diet.Almost 40% of the extra duodenal energy on the pelleted diet was due to increased cellulose flow, with only 79% of digestible cellulose being digested in the rumen compared with 96% on the other two diets. There was an associated decrease in ruminal volatile fatty acid production of approx. 20%. Approximately half of the extra energy was due to an elevated flow of protein on the pelleted diet, but this increase was not reflected in amino acid absorption due to a reduced efficiency with the dried diets (frozen 72%, dried diets 54%).The results demonstrate that dehydration and processing of red clover can markedly influence nutrient digestion and supply and thus offer attractive means of improving the nutritive valu

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1981.tb01557.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe data from 12 individual cattle grazed on a uniform sward were used to compare field sampling of faeces with three time‐schedules for rectal sampling of faeces. Estimates of digestibility from a faecal nitrogen equation were compared with estimates based onin vitrodigestibility, or modified acid‐detergent fibre determinations, on clipped herbage samples.Field sampling gave a lower coefficient of variation (8%) in chromic oxide content than did grab sampling (14%). Grab sampling introduced an upward bias in estimates of faecal output compared with field samples. The estimate of digestibility based on the faecal index was intermediate to those based on clip samples from the upper and lower horizons of the sward. There was no difference in the mean digestibilities estimated fromin vitroor MAD fi

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1981.tb01558.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractWhite clover (cv. S184 or Blanca) or marsh trefoil (cv. Grasslands 4703 or Grasslands Maku) were sown alone and in combination with a companion grass (tall fescue, red fescue, perennial ryegrass or ryegrass cleanings) on a peat area of hill land originally dominated byJuncus articulatusandMolinia caerulea.Lime and ground rock phosphate were applied in 1973, the area rotavated to a shallow depth and seeds sown in May 1974. No fertilizers were applied except at sowing time and two harvests were taken per annum for 4 years.Differences in yield and legume content between companion grass treatments were small. After the first full harvest year Blanca swards usually had the lowest DM yields and those containing Maku the highest. The contribution of marsh trefoil to total herbage yield increased from 4·2% in 1975 to 22% in 1978, whereas white clover decreased from 4·2 to 1·2%. Legume yields in 1978 were less than half those in 1977. Overall, N yields were low, Maku swards fixing most N estimated to be highest in 1977 at 35 kg ha‐1.It is concluded that marsh trefoil grows well on upland peat but more information on its response to grazing is necessary before conclusions can be drawn about its value in hill land improve

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1981.tb01559.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractSwards ofL. perenneandP. annuawere treated at the 2–3 leaf stage with recommended rates of ethofumesate (5 and 10 kg a.i. ha‐1).P. annuaceased normal growth, became swollen at the shoot base and eventually showed signs of senescence.L. perenneshowed no visible defects, treated swards being more vigorous than untreated. Scanning electron micrographs showed that the developing leaf primordia ofP. annuahad been affected by the ethofumesate. In both grass species, ethofumesate induced abnormalities in cell division. These abnormalities caused irreversible damage toP. annuabut only slight distortion ofL. perennewhich later recovered and resumed normal growth. More detailed biochemical studies are required to determine the specific effects of ethofumesate on cell gro

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1981.tb01560.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY