摘要:

AbstractThe effects of stocking rate and N fertilizer on a mixed sward of perennial ryegrass (Lolium perenne)and white clover (Trifolium repens) set‐stocked with sheep were examined. Sward production and composition, and sheep production were studied.Increasing the stocking rate over the range 25–55 yearling sheep ha−1reduced herbage accumulation by about 40%, whether or not N fertilizer was applied. Increasing the stocking rate increased the density of ryegrass tillers, but reduced the density of clover stolons and the clover content of the swards. Applications of N fertilizer (200 kg N ha−1a−1) increased herbage accumulation by about 20% but substantially reduced the clover content.Liveweight gain per animal and per unit area were greater at the lower stocking rates where the clover content and nutritive value of the diet were greatest. Wool growth per unit area was greater at the higher stocking rates. Applications of 1M fertilizer increased liveweight gain at stocking rates above 25 sheep ha−1, but had no effect on wool production at any stocking rate.The results demonstrate that a stable and productive grass‐clover association was maintained under conditions of set‐stocking at around 23 yearling sheep ha−1and that at this stocking rate, which appears to be about the biological optimum, there was no advantage in u

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1985.tb01730.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractFour stocking rates (25–55 sheep ha−1) and two N fertilizer treatments (nil or 200 kg N ha−1) were imposed on swards containing perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) which were continuously stocked throughout one grazing season. These treatments gave swards that varied greatly in their content of white clover. The effects of these treatments on pasture and animal performance in the following season were examined when all plots were continuously‐stocked with 25 yearling sheep ha−1and received no N fertilizer. There was slight regeneration of clover in the second year. Herbage growth ranged from 5.4 to 11.0 t dry matter (DM) ha−1, was closely correlated with the clover content of the swards and was higher on swards that had previously received 0 rather than 200 kg Nha−1.The liveweight gain and wool production of sheep in the second grazing season closely reflected the herbage growth and clover content of the swards. As a result, animal production was greatest from swards which had previously been stocked at the lowest rate and had received no N fertilizer and least from swards which had been stocked at the lowest rate but had received N fertilizer.The results show that the adverse effects of over‐grazing and N fertilizer application in one season may be partially rectified by lower stocking rates and by withholding N fertilizer in the f

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1985.tb01731.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractItalian, perennial, hybrid ryegrass, tall fescue and cocksfoot were used to determine the influence of the weather upon grass growth. Throughout the spring and summer months of 1975 and 1976, weather conditions were monitored. Crop growth rate, leaf extension rate, leaf appearance rate and tillering were recorded. Natural (control), covered and irrigated treatments were applied. In spring, crop growth rates were correlated with solar radiation and temperature, but growth rates were greatest at high levels of insolation. Leaf extension rate was associated with temperature during spring. But during summer this association between temperature and leaf extension became confused as soil water deficit increased. Leaf extension rate in the tall fescue variety SI 70 was the slowest of all for a given temperature. In 1975 leaf growth was very sensitive to temperature; the rate of leaf appearance increased as temperature increased. In 1976 water deficit reduced crop growth rate in spring, and was the major factor influencing crop growth rates in all varieties during summer. Leaf extension and leaf appearance rates were both reduced by increasing soil water deficit. The ryegrasses appeared most sensitive to drought and poor recovery growth was found in the Italian RvP and the hybrid Snowdon.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1985.tb01732.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractFaba beans and peas were compared as spring sown whole‐crop forages in two trials at Lough‐gall. No herbicide, insecticide or N fertilizer was used. Harvesting took place at the end of July. As pure stands, tic beans (cv. Blaze) yielded up to 10 t of dry matter (DM) ha−1. Lower yields were obtained at lower seed rates, or with horse beans (cv. Stella Spring), broad beans (cv. Polar) or peas (cvs Minerva and Krupp). Tic and horse bean forage had a mean DM concentration of 166 g kg−1, which was higher than those of broad bean and peas. Crude protein (CP) concentration at a mean of 159 g kg−1was similar in tic beans and peas. Faba beans mixed with cereals yielded less than beans alone, but peas with cereals yielded slightly more than peas alone. The inclusion of a cereal raised forage DM contents but lowered CP contents. Perennial ryegrass‐white clover mixtures undersown in faba beans established well, but poorer swards were obtained in some of the pure pea stands which lodged severely. It is concluded that, as pure stands, tic beans have advantages over peas. Some of the disadvantages of peas can be overcome by growing a mixture of peas w

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1985.tb01733.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractRoot competition was studied between seedlings of green panic (Panicum maximumvar.trichoglume) andHeteropogon contortusin a native grassland sward clipped regularly to a height of 5·7 cm, and to which supplementary irrigation was applied. The influence of fertilizer addition and root competition from the grassland sward on seedling growth during the 42 days following emergence was determined. Root competition was excluded by steel tubes, or eliminated by killing the native sward with herbicides.Seedling growth was poor where neither root competition was controlled nor fertilizer was applied; at 42 days the seedlings were still less than 6 cm high with three leaves and one tiller. When root competition was controlled, either by steel tubes or herbicide, seedling growth increased significantly. Growth was greatest in the herbicide‐treated plots where fertilizer was applied, seedlings at day 42 being 48 cm high with sixty‐three leaves and nineteen tillers.Competition for nutrients appeared to be the primary factor limiting seedling growth and this was largely overcome by fertilizer application. Competition for nutrients appeared to increase the fertilizer requirements of pastures oversown into live swards compared with that of pastures oversown into herbicide‐treated

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1985.tb01734.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractAn experiment is described in which steers and wether sheep separately grazed perennial ryegrass swards, managed so that half of each sward had previously been grazed by sheep and half by cattle. The influence of the presence of dung from the same or the other species on grazing patterns and herbage utilization was examined.Regression analysis of extended sward height along transects laid across dung pats after grazing revealed that the limits of the rejected herbage were more clearly defined around cattle dung than sheep dung when grazed by cattle, whereas there was less distinct avoidance of herbage around both cattle and sheep dung when grazed by sheep. As grazing proceeded there was a progressive movement of animals from the half of the plot previously grazed by the same species to the half previously grazed by the opposite species, and this movement was more marked in the cattle than in the sheep.It was concluded that under mixed grazing a greater proportion of the herbage would be available to the sheep giving them an advantage over the cattle.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1985.tb01735.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractFor three 8‐week periods of the grazing season 48 spring‐calving cows were continuously stocked at either a high or a low rate (average 4.9 and 4.3 cows ha−1respectively) which declined through the season. Within each stocking rate group half the cows were allowed access to hay for 45 min after morning milking; the other half received no hay.Total dry matter (DM) intakes were increased by offering hay, and intakes of hay were greater at the high stocking rate and during prolonged periods of inclement weather. However, there were times when, because of low herbage height and adverse weather, offering hay once daily could not prevent a decline in total DM intake. Grazing time was reduced and ruminating time increased by offering hay, but the rate of biting at pasture was unaffected. Hay DM was eaten at twice the rate of intake of herbage DM.Offering hay increased milk yield in early season and liveweight gain in late season. The benefits of offering hay were greatest for the higher yielding cows. There were no significant effects on milk composition.Stocking rate had only small effects on herbage height, but stocking at the higher rate tended to reduce herbage DM intake and reduced live‐weight gain in late season. Levels of utilized metabolizable energy from grazed herbage were high (average 106 GJ ha−1) but were reduced by feeding hay and stocking at the l

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1985.tb01736.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractGrass silage was offered to continuously stocked dairy cows in two experiments. In the first 12 weeks of the grazing season (Experiment 1) 32 cows were offered grazed herbage only (G), or grazed herbage with a silage supplement offered for 45 min after morning milking (GMS), overnight at a restricted level (GRS) or overnightad libitum(GAS). The two overnight treatments involved housing the cows between afternoon and morning milking. In late season (Experiment 2) 18 cows were used in a similar experiment lasting 9 weeks to compare treatments G, GMS and GAS. Within experiments the same level of herbage was available to all treatments (mean sward height 9.6 and 7.2 cm in Experiments 1 and 2 respectively).In Experiment 1, offering silage depressed herbage dry matter (DM) intake but had no significant effect on total DM intake. Silage (GMS, GRS, GAS) reduced milk yield but increased milk fat content and fat yield compared with G. In Experiment 2 offering silage depressed herbage DM intake but increased total DM and ME intakes. This led to increased milk yields, fat and lactose contents and liveweight gains, with the greatest benefit obtained when silage was available overnight.Silage was therefore beneficial in maintaining high DM intakes. Also, the substitution of silage for grazed herbage, particularly in Experiment 2, indicated that high stocking rates on grazing land can be maintained throughout the season, when silage is availablead libitum.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1985.tb01737.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractContinuous hourly measurements of air and soil temperatures, irradiance and wind velocity, and less frequent measurements of soil water status and dry matter (DM) yield were recorded over two growing seasons and the intervening winter 1978–79 for an enclosed upland grassland in Cumbria, with the aim of establishing realistic combinations of environmental factors for the design of experiments under controlled conditions. Important features of the microclimate included high diurnal and day‐to‐day variation in environmental temperature, relatively high winter soil temperatures, variation between years in the influence of altitude upon irradiance, low wind velocity throughout the year at plant height and the loss of DM yield in the early summer of 1978 due to severe drought. Combinations of environmental factors throughout the 2 years can be obtained from the figures presented; in particular, the records indicate that in growth‐cabinet or greenhouse experiments associated with the breeding or selection of cultivars for earlier DM production in spring, it is important to combine low temperatures (≤ 10°C) with realistic levels of irradiance (≥200 W m−2) and dayleng

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1985.tb01738.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractPermanent pasture in the Po Valley of Italy was the site of a pluriannual experiment (1975–81) to observe the effects on hay production of N and P fertilizer applications well above those normally recommended. A split‐plot design with a randomized complete block arrangement of the whole‐plot factor with 5 levels of N and the subplot factor with 3 levels of P was chosen for the experiment. The maximum rate of N application was 800 kg ha−1while the corresponding rate for P was 87.3 kg ha−1. Principal species in the sward were orchard grass (Dactylis glomerataL.), perennial ryegrass (Lolium perenneL.), common velvetgrass (Holcus lanatusL.) and white clover (Trifolium repensL.).This field was irrigated according to customary techniques during summer months and cut five limes each year. Yields were analysed by means of a response function of the linear and plateau type which incorporates von Liebig's Law of the Minimum, it was found that this function represents the hay response very well with respect to N. In fact, beyond 390 kg ha−1applied N the response is negligible up to 800 kg ha−1, the maximum rate tested in this experiment. The optimal rate of applied N decreased consistently over the years from 390 to 260 kg ha−1. At these unusually high levels of fertilization hay production increased about 60–80% compared with normal practices.The estimation of the von Liebig response function requires mathematical programming knowledge. The estimates obtained are maximum likelihood estimates. The practical importance of estimating and using this response function lies in its ability to achieve the maximum response with the minimum amount of fertilizers among all other admissible response functions. Hence, its adoption for making fertilizer recommendations would save farmers money and limit chemical pollution t

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1985.tb01739.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY