Brookes, I. M.

Horne, David J.

Thatcher, A. R.

English

University of Kentucky

University of Kentucky UKnowledge International Grassland Congress Proceedings 21st International Grassland Congress / 8th International Rangeland Congress Urinary‐Nitrogen Output by Dairy Cows in Conventional and Organic Grazing Systems I. M. Brookes Massey University, New Zealand David J. Horne Massey University, New Zealand A. R. Thatcher Massey University, 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/21/9-1/19 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 Ⅱ 　 瞯 ]35　 瞯Grasslands/Rangelands Production Systems——— Livestock Production SystemsUrinary‐nitrogen output by dairy cows in conventional and organic grazing systemsI .M .Brookes ,D .J .Horne and A .R .ThatcherCollege o f Sciences ,Massey University ,Priv ate Bag 11‐222 ,Palmerston North ,New Zealand .E‐mail : I .B rookes＠ massey .ac .nzKey words : organic dairying ,urine output ,nitrogen losses ,pasture feedingIntroduction Urine from cows grazing pastures with high crude protein ( CP) concentrations is the major source of nitrogen ( N )leached in drainage water from New Zealand dairy farms .Organic dairy systems ,using limited fertiliser N and supplements ,areconsidered more environmentally friendly . This paper provides measurements and predictions of N leaching losses in a farmletstudy ,comparing conventional and organic dairy systems .Method Two ２０ ha farmlets at Massey University are managed as either a conventional seasonal‐supply dairy farm (C ) or as afully‐certified organic system ( O ) .Nitrogen fertiliser is applied to C at a rate of １４０ kg N / ha/ year ,while O has minimal Napplied as chicken manure .The average annual pasture yields are １１ .４ and １０ .３ tonnes dry matter ( DM ) / ha for C and Orespectively .The farmlets are stocked at ２ .４ ( C) and ２ .２ ( O ) cows/ ha ,producing ４０９ ( C) and ３４５ ( O ) kg milksolids ( MS) /cow and ９８０ ( C) and ７７０ ( O ) kg MS / ha .Cows are grazed off‐farm for six weeks from June １st .Annual N losses in drainagewater for winter‐spring in ２００３‐２００６ averaged １９ ( C ) and ８ ( O ) kg N / ha .To further investigate N leaching ,intensivemonitoring of milk urea‐N concentrations ( an indirect measure of urinary‐N output ) ,cow live weight and body condition ,andpasture CP on both farmlets was carried out from September to January ２００５ /６ .Annual DMI intakes were estimated from２００５ /６ MS yields ( C : ３９８ ; O : ３２０ kg /cow ) .Differences in pasture CP concentrations in other months of the year wereassumed to be similar to those in the monitoring period .Urinary‐N outputs were estimated by the Cornell Net Carbohydrate andProtein System model ( Fox et al . ,２００４ ) ,and leaching losses by the Nitrogen Leaching Estimation ( NLE) model of Di &Cameron (２０００ ) and Overseer Nutrient Budgeting software (Wheeler et al . ,２００３) .Results Over the five‐month monitoring period ( Table １ ) shows decreases in dietary CP％ ,(２０％ ) ,N‐intake/ cow ( ３０％ ) ,milkurea‐N (３０％ ) and urine‐N /cow (４３％ ) for farmlet O .In ２００５ /６ ,annual urine‐N / ha was estimated to be ３８％ lower on farmletO ( Table ２) .All methods of assessing N‐leaching estimated O drainage N‐loss to be ～ ５０％ of that from C .Table 1 N intake ,urine N output and milk urea‐N f ormonitoring period (sep‐Jan ２００５１６ ) .Farmlet C OStocking rate (Cows/ ha) ２ 媼.４ ２ H.２Milksolids Yield ( kg / cow ) ２８８ 珑２４０ いDM intake ( kg / cow ) ２５１４ 珑２１７９ いDietary CP ( ％ of DM ) ２３ 媼.４ １８ H.９N intake ( kg / cow ) ９４ 珑６６ いMean Milk Urea N (mmol/ Litre) ５ 媼.１ ３ H.６Urine N output ( kg / cow ) ５０ 珑２９ い( kg / ha) １２１ 珑６４ いTable 2 N intake ,urine N output and N leaching .A nnualestimates ２００５１６ .Farmlet C OStocking rate (Cows/ ha) ２  .４ ２ 噰.２DM intake ( kg / cow ) ４４２６ `４１２０ 沣Dietary CP ( ％ of DM ) ２２  .７ １８ 噰.６N intake ( kg / cow ) １６１ `１２３ 沣Urine N output ( kg / cow ) ９０ `５９ 沣( kg / ha) ２１５ `１３３ 沣N in urine patches 倡 ( kg / ha) １１２３ `７４２ 沣N leached‐NLE model ( kg N / ha) １５ `７ 沣N leached‐Overseer model ( kg N / ha) １６ `８ 沣倡 Assumes urine from a cow covers ～ ０ .０８ of the areaConclusion Urine‐N output and N leaching losses were markedly lower on the organic farmlet ,which is a reflection of the lowerstocking rates ,DM intake/ cow and dietary CP％ compared with the conventional farmlet .ReferencesDi ,H .J .& K .C .Cameron ( ２０００) . Calculating nitrogen leaching losses and critical nitrogen application rates in dairy pasturesystems using a semi‐empirical model . N Z Journal of Agricultural Research ,４３ ,１３９‐１４７ .Fox ,D .G ,L .O .Tedeschi ,T .P .Tylutki ,J .B .Russell ,M .E .Van Amburgh ,L .E .Chase ,A .N .Pell & T .R .Overton ( ２００４) .TheCornell Net Carbohydrate and Protein System model for evaluating herd nutrition and nutrient excretion . A nimal FeedScience and Technology ,１１２ ,２９‐７８ .Wheeler ,D .M ,S .F .Ledgard ,C .A .M .de Klein ,R .M .Monaghan ,P .L .Carey ,R .W .McDowell & K .L .Johns ( ２００３ ) .OVERSEERTM nutrient budgets — moving towards on‐farm resource accounting .Proceedings o f the New Zealand GrasslandA ssociation , ６５ ,１９１‐１９４ .

Urinary‐Nitrogen Output by Dairy Cows in Conventional and Organic Grazing Systems

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Urinary‐Nitrogen Output by Dairy Cows in Conventional and Organic Grazing Systems

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