Publication Date
1989
Description
Relatively little is known about the growth of tall fescue under continuous grazing. Most of reported works about herb age production in such a grazing management have been done with perennial ryegrass and with relatively high levels of nitro gen fertilisation (Hodgson, 1981 ; Bircham, 1981; Parsons et al., 1983). The effect ot the level N nutrition on growth of a continuously grazing sward has not been yet studied. On intermitently defoliated swards of tall fescue, Gastal & Lemaire (1988) have shown that with non limiting level of N nutrition the increase in dry matter production could be 4 or 5 time higher than that of unfertilised swards. 50 % of this increase were explained by an increase of the quantity of the P.A.R. intercepted by the sward as a consequence of a more rapid L.A.I. development. These authors have also demonstrated that only 20 % of the supplemental dry matter yield were explained by a direct effect of N on leaf photosynthetic capacity. So they hypothesized that the rest (30 %) could be attributed to a change in assimilate partitionning between shoots and roots. In continuously grazing conditions, the effect of N on leaf area expansion is continuously removed by supplemental graz ing animals adjusted to maintain the sward surface height and L.A.I. at optimum level. So we can expect that in these conditions at least 50 % of the effect of nitrogen would disappear, compared to intermitently defoliated swards. In order to verify this hypothesis we have set up an experiment on two genotypes of tall fescue differing by their tillering ability ( cv Clarine : low tiller density, and cv Barcel: high tiller density).
Citation
Mazzanti, A; Lemaire, G; and Gastal, F, "Effect of Nitrogen on Herbage Growth and Intake by Sheep in Continuously Grazed Swards of Tall Fescue Genotypes" (2025). IGC Proceedings (1989-2023). 96.
https://uknowledge.uky.edu/igc/1989/session1/96
Included in
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Effect of Nitrogen on Herbage Growth and Intake by Sheep in Continuously Grazed Swards of Tall Fescue Genotypes
Relatively little is known about the growth of tall fescue under continuous grazing. Most of reported works about herb age production in such a grazing management have been done with perennial ryegrass and with relatively high levels of nitro gen fertilisation (Hodgson, 1981 ; Bircham, 1981; Parsons et al., 1983). The effect ot the level N nutrition on growth of a continuously grazing sward has not been yet studied. On intermitently defoliated swards of tall fescue, Gastal & Lemaire (1988) have shown that with non limiting level of N nutrition the increase in dry matter production could be 4 or 5 time higher than that of unfertilised swards. 50 % of this increase were explained by an increase of the quantity of the P.A.R. intercepted by the sward as a consequence of a more rapid L.A.I. development. These authors have also demonstrated that only 20 % of the supplemental dry matter yield were explained by a direct effect of N on leaf photosynthetic capacity. So they hypothesized that the rest (30 %) could be attributed to a change in assimilate partitionning between shoots and roots. In continuously grazing conditions, the effect of N on leaf area expansion is continuously removed by supplemental graz ing animals adjusted to maintain the sward surface height and L.A.I. at optimum level. So we can expect that in these conditions at least 50 % of the effect of nitrogen would disappear, compared to intermitently defoliated swards. In order to verify this hypothesis we have set up an experiment on two genotypes of tall fescue differing by their tillering ability ( cv Clarine : low tiller density, and cv Barcel: high tiller density).
