Adamczewski, K. A.

Burkitt, L. L.

Donaghy, Danny J.

Turner, Lydia R.

English

University of Kentucky

University of Kentucky UKnowledge International Grassland Congress Proceedings 21st International Grassland Congress / 8th International Rangeland Congress Changes in the Physiology of Tall Fescue during Regrowth Danny J. Donaghy University of Tasmania, Australia L. R. Turner University of Tasmania, Australia K. A. Adamczewski University of Tasmania, Australia L. L. Burkitt University of Tasmania, Australia Follow this and additional works at: https://uknowledge.uky.edu/igc  Part of the Plant Sciences Commons, and the Soil Science Commons This document is available at https://uknowledge.uky.edu/igc/21/3-1/12 The 21st International Grassland Congress / 8th International Rangeland Congress took place in Hohhot, China from June 29 through July 5, 2008. Proceedings edited by Organizing Committee of 2008 IGC/IRC Conference Published by Guangdong People's Publishing House This Event is brought to you for free and open access by the Plant and Soil Sciences at UKnowledge. It has been accepted for inclusion in International Grassland Congress Proceedings by an authorized administrator of UKnowledge. For more information, please contact UKnowledge@lsv.uky.edu. 　 Multifunctional Grasslands in a Changing World 　 Volume Ⅰ 　 瞯 ]445　 瞯Grasslands/Rangelands Resources and Ecology ——— Soil‐Plant‐Animal InterrelationshipsChanges in the physiology of tall fescue during regrowthD .J . Donaghy 倡 ,L .R . Turner , K .A . A damczewski and L .L . BurkittTasmanian Institute o f A gricultural Research , University o f Tasmania , Burni ,e Tasmania .倡 Corresponding author . E‐mail : Danny .Donaghy＠ utas .edu .auKey words : herbage quality , regrow th , tall fescueIntroduction Tall fescue ( Festuca arundinacea Schreb .) is a widely utilised dairy pasture species due to its wide range ofadaptability ( Langer , １９９０) , but little is known about the effect of leaf stage based defoliation management on this species .Grazing management decisions should be based on an understanding of the physiological changes that occur in the grass plantthroughout the regrow th cycle . The aim of the present study was to investigate changes in tall fescue during regrow th toestablish a basis for optimum defoliation management of tall fescue pastures .Materials and methods Glasshouse treatments consisted of one preliminary harvest followed by ５ sequential harvests when eachnew leaf had regrown , up to the ５‐leaf stage (５ live leaves per tiller) . Leaf tissue , stubble tissue below ５０ mm and roots werecollected at each harvest . Root and stubble samples were analysed for water‐soluble carbohydrates (WSC) , and metabolisableenergy ( ME) was calculated using dry matter (DM ) digestibility measurements of leaf material .Results and discussion A positive linear relationship ( r２ ≥ ０ ．６１） between stubble WSC levels and the regrow th capacity of tallfescue confirmed that WSC reserves play an important role in the entire plant regrow th cycle following defoliation . Leaf androot regrow th commenced at a similar time in tall fescue plants following defoliation , with both leaf and root DM yields reachingtheir pre‐defoliation levels between the ２‐leaf and ３‐leaf stages . Root grow th increased until the ４‐leaf stage and then stabilized ,while leaf grow th continued to increase until the ５‐leaf stage of regrow th . Leaf and root grow th , therefore , appeared to beassigned equal priority for energy allocation , unlike perennial ryegrass ( Lolium perenne L .) , for which leaf regrow th has ahigher priority for allocation of WSC reserves following defoliation compared with roots (Donaghy and Fulkerson , １９９８) . Thisfinding is in agreement with the work of Kemp et al . (２００１ ) , who found that tall fescue allocated more of its biomass to rootsand pseudostem compared with perennial ryegrass . The ME concentration of tall fescue decreased with increasing leaf stage( Table １) , due to decreasing digestibility of plant tissue with age .Table 1 Stubble dry matter (DM ) (mg/ tiller) , root and leaf DM (mg/ p lant) , and lea f metabolisable energy (ME) (M J/ kgDM) be f ore de f oliation and at each corresponding lea f regrow th stage .Leaf regrow th stage( leaves/ tiller)Stubble DM( g / plant)Root DM( g / plant)Leaf DM( g / plant)Leaf ME(MJ/ kg DM )０ 後０ 侣.８７ １ ＃.５０ ３ 剟.９４ １０ 摀.７１ 後０ 侣.６９ ０ ＃.８０ ０ 剟.５６ １１ 摀.３２ 後０ 侣.８９ １ ＃.２９ ２ 剟.４８ １０ 摀.９３ 後０ 侣.８９ １ ＃.６５ ４ 剟.３７ １０ 摀.４４ 後１ 侣.１７ ２ ＃.１９ ６ 剟.７５ １０ 摀.１５ 後１ 侣.４４ ２ ＃.０９ ７ 剟.１１ ９ e.２LSD ( P ＝ ０ �.０５) ０ 侣.２９ ０ ＃.６２ ０ 剟.９１ ０ e.２Conclusions These results emphasise the dichotomy of this species , with relatively frequent defoliation at the ２‐leaf stagerequired to maintain an ME concentration above １０ .５ MJ kg‐１ DM , contrasting with relatively infrequent defoliation at the ４‐leaf stage required to maximise pasture production and persistence . A field study investigating the rotational grazing of tallfescue at different leaf regrow th stages would be valuable to confirm the most effective range of grazing intervals in the field .ReferencesDonaghy , D .J . , Fulkerson , W .J . ,( １９９８ ) . Priority for allocation of water‐soluble carbohydrate reserves during regrow th ofLolium perenne ( L ) . Grass Forage Science ５３ , ２１１‐２１８ .Kemp , P .D . , Tavakoli , H . , Hodgson , J . ,( ２００１ ) . Physiological and morphological responses of tall fescue and perennialryegrass to leaf defoliation . Proc . １０th Aust . Agron .Conf . , A ustralian Society o f A gronomy , Hobart .Langer , R .H .M . ,(１９９０) . Pasture plants . In : Langer , R .H .M . Pastures‐their ecology and management . Auckland : OxfordUniversity Press , ３９‐７４ .

Changes in the Physiology of Tall Fescue during Regrowth

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Changes in the Physiology of Tall Fescue during Regrowth

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