Donaghy, D. J.

Lee, Julia M.

Roche, J. R.

Sathish, P.

English

University of Kentucky

University of Kentucky UKnowledge International Grassland Congress Proceedings 21st International Grassland Congress / 8th International Rangeland Congress Effect of Defoliation Frequency and Severity during Winter on Herbage Regrowth and Water‐Soluble Carbohydrate Content of Perennial Ryegrass (Lolium perenne L.) Dominant Swards Julia M. Lee DairyNZ, New Zealand D. J. Donaghy TIAR, Australia P. Sathish Pastoral Genomics, New Zealand J. R. Roche DairyNZ, New Zealand 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/21/9-1/40 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. 瞯 ]56　 瞯 　 Multifunctional Grasslands in a Changing World 　 Volume Ⅱ 　Grasslands/Rangelands Production Systems——— Livestock Production SystemsEffect of defoliation frequency and severity during winter on herbage regrowth and water‐solublecarbohydrate content of perennial ryegrass ( Lolium perenne L .) dominant swardsJ .M .Lee1 ,D .J .Donaghy 2 ,P .Sathish3 ,J .R .Roche11 DairyNZ ,Priv ate Bag 3221 , H amilton New Zealand 2 T IA R , PO Box 3523 , Burnie TA S 7320 A ustralia 3 PastoralGenomics ,c /o V iaL actia Biosciences ,PO Box 109185 ,A uckland ,New Zealand . E‐mail : j ulia .lee＠ dairynz .co .nzKey words : defoliation frequency ,defoliation severity ,perennial ryegrass ,water‐soluble carbohydratesIntroduction Perennial ryegrass is one of the world摧s primary grazed grasses in temperate regions .To retain the low costs ofproduction vital to the prosperity of industries that rely on ryegrass ,it is necessary to maximise herbage grow th .Grazingmanagement decisions can have a positive or negative impact on regrow th .Although results have been inconsistent ,two suchdecisions include the frequency and severity with which swards are defoliated .Methods The interaction between defoliation frequency and severity was investigated in a ２ ( f requency) x ３ ( severity) factorialarrangement .Swards were defoliated either three times at the １‐leaf ( frequently ; F ) or once at the ３‐leaf ( infrequently ; IF )stage of regrow th to ４０ mm residual stubble height ( RSH ) .At the third harvest for the frequently defoliated swards and thefirst for the infrequently defoliated swards ,swards were defoliated to ２０ ,４０ or ６０ mm RSH ( H１ ; late winter) .All swards wereallowed to regrow to the ３‐leaf stage before a final defoliation to their treatment RSH ( H２ ; mid spring ) .The water‐solublecarbohydrate (WSC) content of ryegrass tillers below the treatment RSH was determined post‐defoliation ,and at each leaf stagebetween H１ and H２ using a modification of the method described by Smith (１９６９) .　 　 　 Figure 1 Water‐soluble carbohydrate ( W SC ) content below thetreatment residual stubble height ( RSH ) o f perennial ryegrasstillers de f oliated three times at the １‐lea f stage ( dashed lines )or once at the ３‐lea f stage (solid lines ) to ２０ ( △ ▲ ) ,４０ ( □ ■ )or ６０ ( ○ ● ) mm RSH and allowed to regrow to the ３‐leafstage .Results Frequently defoliated swards yielded lessherbage up to ,and including ,H１ （９６６ vs .１３６１ kgDM /ha for F and IF defoliated swards ,respectively ; P ＜ ０ .００１ ) and again at H２ （２００７vs .２２７９ kg DM / ha ; P ＜ ０畅００１ ) . Defoliatingswards to ６０ mm reduced herbage production at H２（２２６６ ， ２２４９ and １９１４ kg DM / ha for swardspreviously defoliated to ２０ , ４０ and ６０ mm ,respectively ; P ＜ ０ . ００１ ) . The post‐defoliationWSC content in ryegrass stubble was reduced byboth frequent and severe defoliation ( Figure １ ; P＜ ０ . ００１ ) . By the ２‐leaf stage , the effect ofdefoliation frequency had dissipated ( P ＞ ０ .１ ) ,although the effect of defoliation height remained( P ＜ ０ .００１ ) . Contrary to previous glasshouseresearch ,there was no correlation between post‐defoliation WSC content and subsequent herbageyield .Frequently defoliated swards had both lowerWSC content and herbage yield than those lessfrequently defoliated ,whereas swards defoliated to６０ mm had higher WSC content ,but lower yieldsthan those defoliated to ２０ or ４０ mm . Furtherinvestigation is required to determine theimportance of WSC on the yield of field‐grownryegrass .Conclusions Frequent defoliation of swards at the １‐leaf stage reduced herbage production ,even if management then allowedregrow th to the recommended defoliation stage ( ３‐leaf ) .During winter ,it was possible to defoliate swards more severely thanhas been recommended during spring‐autumn (４０‐８０ mm ; Lee et al . ,２００８) or from glasshouse studies ( ５０ mm ; Fulkerson etal . ,１９９４ ) ,w ithout adversely affecting herbage production .ReferencesFulkerson ,W .J . ,Slack ,K .& Lowe ,K .F .( １９９４ ) Variation in the response of Lolium genotypes to defoliation .A ustralianJournal o f A gricultural Research ,４５ : １３０９‐１３１７ .Lee ,J .M . ,Donaghy ,D .J .& Roche ,J .R .( ２００８ ) Effect of defoliation severity on regrow th and nutritive value of perennialryegrass ( Lolium perenne L .) dominant swards .A gronomy Journal , １００ : in press .Smith ,D . ( １９６９ ) Removing and analysing total non‐structural carbohydrates from plant tissue .W isconsin A griculturalEx perimental Station Research Report ,４１ : １‐１１ .

Effect of Defoliation Frequency and Severity during Winter on Herbage Regrowth and Water‐Soluble Carbohydrate Content of Perennial Ryegrass (\u3cem\u3eLolium perenne\u3c/em\u3e L.) Dominant Swards

https://uknowledge.uky.edu/cgi/viewcontent.cgi?article=3021&amp;context=igc

Effect of Defoliation Frequency and Severity during Winter on Herbage Regrowth and Water‐Soluble Carbohydrate Content of Perennial Ryegrass (\u3cem\u3eLolium perenne\u3c/em\u3e L.) Dominant Swards

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