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G. L. Santos - One of the best experts on this subject based on the ideXlab platform.

  • Leaf growth and utilization in four grass species under steady state Continuous Grazing
    The Journal of Agricultural Science, 1995
    Co-Authors: J. R. B. Tallowin, S. K. E. Brookman, G. L. Santos
    Abstract:

    Tiller weight, lamina length, lamina growth rate, appearance interval and lamina utilization were examined in Lolium perenne, Agrostis stolonifera, Holcus lanatus and Poa trivialis. Marked tillers were measured in situ over 1421 day periods in a Continuously grazed permanent pasture under steady state management in Devon, UK in 1985, 1986 and 1987 on plots receiving either zero (0N) or 400 kg nitrogen (400N) fertilizer/ha per annum. L. perenne was incapable of reducing its individual tiller weight or lamina length to the same extent as in the other three species during the Grazing season. Lamina appearance interval was longer in L. perenne than in the other three species in most of the observation periods in both the 400N and 0N plots. Overall the lamina appearance intervals were similar between A. stolonifera, H. lanatus and P. trivialis. Lamina extension rates were greater in L. perenne than in either A. stolonifera or P. trivialis in most observation periods in both plots. H. lanatus had lower lamina extension rates than L. perenne in c. 50% of the observation periods in both plots, at other times the extension rates of the two species were similar, with one exception in early spring in the 400N plot when H. lanatus had a higher extension rate. There was no clear pattern in seasonality as to when H. lanatus had a lower extension rate than L. perenne. H. lanatus achieved either similar or higher lamina extension rates than either A. stolonifera or P. trivialis in c. 50% of the observation periods, respectively; the periods when higher rates were observed in H. lanatus in the 400N plot occurred mainly in the spring and early summer. A. stolonifera and P. trivialis achieved similar lamina extension rates in most observation periods in both the 0N and 400N plots. The specific differences observed in the lamina extension rates were emphasised when converted to growth rates by multiplying the length increments by the average weight per unit length of the expanded lamina for each species. Lamina utilization, in terms of percentage of lamina length removed by Grazing, was similar between the four grass species in most observation periods in the 0N plot. A. stolonifera lost more lamina length than either L. perenne or P. trivialis in May and June and H. lanatus lost a greater percentage of lamina length than either L. perenne or P. trivialis in May in the 0N plot. In the 400N plot L. perenne lost a greater percentage of lamina length than any of the other species in June and more than P. trivialis in May. A. stolonifera lost a greater percentage of lamina length than any of the other species in July, and more than either L. perenne or P. trivialis in May. This greater severity of Grazing in A. stolonifera was associated with a high incidence of tillers being grazed to stubble. H. lanatus lost more lamina length than L. perenne in May. When the loss of lamina length through Grazing was converted to losses in terms of weight of tissue removed, then L. perenne consistently lost more than either A. stolonifera or P. trivialis in both the 400N and 0N plots. The implications of these differences in tissue production and utilization on competitive interactions between L. perenne and the other three species are discussed

V. H. Burghi - One of the best experts on this subject based on the ideXlab platform.

  • Influence of sward condition on leaf tissue turnover in tall fescue and tall wheatgrass swards under Continuous Grazing
    Grass and Forage Science, 2007
    Co-Authors: M. G. Agnusdei, S. G. Assuero, R. C. Fernández Grecco, J. J. Cordero, V. H. Burghi
    Abstract:

    Summary Two experiments were carried out on a tall fescue sward in two periods of spring 1994 and on a tall wheatgrass sward in autumn 2001 and spring 2003 to analyse the effect of sward surface height on herbage mass, leaf area index and leaf tissue flows under Continuous Grazing. The experiment on tall fescue was conducted without the application of fertilizer and the experiment with tall wheatgrass received 20 kg P ha−1 and a total of 100 kg N ha−1 in two equal dressings applied in March (autumn) and end of July (mid-winter). Growth and senescence rates per unit area increased with increasing sward surface height of swards of both species. Maximum estimated lamina growth rates were 28 and 23 kg DM ha−1 d−1 for the tall fescue in early and late spring, respectively, and 25 and 36 kg DM ha−1 d−1 for tall wheatgrass in autumn and spring respectively. In the tall fescue sward, predicted average proportions of the current growth that were lost to senescence in early and late spring were around 0·40 for the sward surface heights of 30–80 mm, and increased to around 0·60 for sward surface heights over 130 mm. In the tall wheatgrass sward the corresponding values during spring increased from around 0·40 to 0·70 for sward surface heights between 80 and 130 mm. During autumn, senescence losses exceeded growth at sward surface heights above 90 mm. These results show the low efficiency of extensively managed Grazing systems when compared with the high-input systems based on perennial ryegrass.

I. Rhodes - One of the best experts on this subject based on the ideXlab platform.

V Pavlu - One of the best experts on this subject based on the ideXlab platform.

  • studying spatial and temporal dynamics of sward structure at low stocking densities the use of an extended rising plate meter method
    Grass and Forage Science, 2003
    Co-Authors: O Correll, J Isselstein, V Pavlu
    Abstract:

    An extended rising-plate-meter method was used to study the spatial and temporal variability of the sward structure of extensively managed pastures over a Grazing season. Two treatments of a long-term Grazing experiment with heifers were investigated: extensive Continuous Grazing (EG) with a target sward height of 10 cm and intensive Continuous Grazing (IG) with a target sward height of 5 cm. Compressed sward height and related herbage mass (HM), dominant plant species and stage of development of phenology were determined at weekly or twice weekly intervals at fixed measuring points. The results demonstrated a strong variability in sward height and HM, especially on the EG treatment. The botanical composition of the standing herbage differed between treatments and between patches of different heights within the same treatment. In areas with a short sward, the herbage was predominantly composed of Agrostis capillaris, Festuca rubra and Trifolium repens. It was more evenly composed and also included taller growing species, such as Alopecurus pratensis and Galium mollugo, in areas with a tall sward. The area potentially available for reproductive development was high in the EG treatment and low in the IG treatment. The method employed proved suitable to provide a detailed description of the dynamics of the sward structure.

J. R. B. Tallowin - One of the best experts on this subject based on the ideXlab platform.

  • Leaf growth and utilization in four grass species under steady state Continuous Grazing
    The Journal of Agricultural Science, 1995
    Co-Authors: J. R. B. Tallowin, S. K. E. Brookman, G. L. Santos
    Abstract:

    Tiller weight, lamina length, lamina growth rate, appearance interval and lamina utilization were examined in Lolium perenne, Agrostis stolonifera, Holcus lanatus and Poa trivialis. Marked tillers were measured in situ over 1421 day periods in a Continuously grazed permanent pasture under steady state management in Devon, UK in 1985, 1986 and 1987 on plots receiving either zero (0N) or 400 kg nitrogen (400N) fertilizer/ha per annum. L. perenne was incapable of reducing its individual tiller weight or lamina length to the same extent as in the other three species during the Grazing season. Lamina appearance interval was longer in L. perenne than in the other three species in most of the observation periods in both the 400N and 0N plots. Overall the lamina appearance intervals were similar between A. stolonifera, H. lanatus and P. trivialis. Lamina extension rates were greater in L. perenne than in either A. stolonifera or P. trivialis in most observation periods in both plots. H. lanatus had lower lamina extension rates than L. perenne in c. 50% of the observation periods in both plots, at other times the extension rates of the two species were similar, with one exception in early spring in the 400N plot when H. lanatus had a higher extension rate. There was no clear pattern in seasonality as to when H. lanatus had a lower extension rate than L. perenne. H. lanatus achieved either similar or higher lamina extension rates than either A. stolonifera or P. trivialis in c. 50% of the observation periods, respectively; the periods when higher rates were observed in H. lanatus in the 400N plot occurred mainly in the spring and early summer. A. stolonifera and P. trivialis achieved similar lamina extension rates in most observation periods in both the 0N and 400N plots. The specific differences observed in the lamina extension rates were emphasised when converted to growth rates by multiplying the length increments by the average weight per unit length of the expanded lamina for each species. Lamina utilization, in terms of percentage of lamina length removed by Grazing, was similar between the four grass species in most observation periods in the 0N plot. A. stolonifera lost more lamina length than either L. perenne or P. trivialis in May and June and H. lanatus lost a greater percentage of lamina length than either L. perenne or P. trivialis in May in the 0N plot. In the 400N plot L. perenne lost a greater percentage of lamina length than any of the other species in June and more than P. trivialis in May. A. stolonifera lost a greater percentage of lamina length than any of the other species in July, and more than either L. perenne or P. trivialis in May. This greater severity of Grazing in A. stolonifera was associated with a high incidence of tillers being grazed to stubble. H. lanatus lost more lamina length than L. perenne in May. When the loss of lamina length through Grazing was converted to losses in terms of weight of tissue removed, then L. perenne consistently lost more than either A. stolonifera or P. trivialis in both the 400N and 0N plots. The implications of these differences in tissue production and utilization on competitive interactions between L. perenne and the other three species are discussed