Kear, M.

Ledgard, Sterwart F.

Lindsey, S. B.

Luo, Jiafa

Sun, W.

English

University of Kentucky

University of Kentucky UKnowledge International Grassland Congress Proceedings 21st International Grassland Congress / 8th International Rangeland Congress Nitrous Oxide Emissions from Dairy Pasture Systems in New Zealand Jiafa Luo AgResearch, New Zealand S. B. Lindsey AgResearch, New Zealand Sterwart F. Ledgard AgResearch, New Zealand W. Sun AgResearch, New Zealand M. Kear AgResearch, 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/21/2-1/32 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 ]327　 瞯Grasslands/Rangelands Resources and Ecology ——— Soil Quality and Plant NutritionNitrous oxide emissions from dairy pasture systems in New ZealandJ . L uo , S .B . L indsey , S .F . Ledgard , W . Sun , M KearA gResearch , Ruakura Research Centre , Priv ate Bag 3123 , H amilton , New Zealand ,E‐mail :j ia f a .luo＠ agresearch .co .nzKey words : dairy farm , nitrous oxide , grazed pasture , maize supplement , New ZealandIntroduction Animal excreta deposited during grazing are the single largest source of nitrous oxide ( N２O) from agriculture inNew Zealand . N２O gas is formed in soils during nitrification and denitrification processes and these processes are affected bymany soil and climatic factors ( e .g . , soil water‐filled pore space (WFPS) and nitrate concentrations) . There are a number ofpossible management options that can reduce N２O emission from dairy farms ( Clark et al . ２００５) . These options include usingrestricted grazing regimes to reduce excreta‐N deposited onto wet soil and using low‐N feed supplements ( e .g . maize) as analternative to using N‐rich pasture . A dairy farm system study was carried out to evaluate effects of these options on N２Oemissions . In this paper we summarise N２O emission data and environmental efficiencies in terms of N２O emissions per unit of milkproduction obtained from this study .Materials and methods The study site contained white clover‐based pasture ( perennial ryegrass , Lolium perenne ; white clover ,T ri f olium repens ) on a poorly drained loam soil . Farm systems included : １ ) Control : a normal rotational pasture grazingregime with a stocking rate of ３ .０ cows ha‐１ ; ２) Maize supplement : a rotational grazing regime with a stocking rate of ３ .８ cowsha‐１ . About ５ tonnes DM ha‐１ of maize silage were brought in annually ; ３) Stand‐off : Same grazing regime and stocking rate asthe control , but cows were kept on stand‐off pads for １８ hours each day with grazing for ６ hours on pasture during the winterperiod . Measurements of N２O were made for two years on the grazed pastures , maize growing land and stand‐off pad ( Luo etal . ２００８a ,b) . The New Zealand IPCC inventory methodology was used to calculate indirect N２O emissions from leached andvolatilised N .Results Nitrous oxide emission rates exhibited marked seasonal variation , largely explained by changes in soil WFPS ( Figure１) . Annual N２O emissions from the grazed dairy pastures were ４ .７ , ４ .０ and ３ .４ kg N２O‐N ha‐１ for the control , maizesupplement and stand‐off treatments , respectively . The N２O emission rate from the maize growing land was ２ .１ kg N２O‐Nha‐１ , and this was equivalent to emission of ０ .１ kg N２O‐N per tonne of maize silage . Emissions of N２O also occurred from thestand‐off pad . Total annual N２O emissions ( including both the field measured and calculated direct and indirect emissions fromall components of the farm systems ) were ７ .７ , ８ .０ and ７ .０ kg N２O‐N per hectare of dairy farm on the control , maizesupplement and stand‐off farm systems ( Table １) . Total N２O emissions per kg of milk production from the maize supplementand stand‐off farm systems were ２２％ and ９％ lower than that from the control system , respectively .　 Figure 1 N２ O emissions as a f f ected by soilW FPS .Table 1 N２ O emissions and env ironmental e f f iciency indicators ( L uoet al . ２００８a ,b) .Control Maizesupplement Stand‐offN２O emissions( kg N２O‐N ha‐１ yr‐１ ) ７ <.７ ８ 种.０ ７ 殚.０Change in N２O emissioncompared to control ( ％ ) ４ 种‐９  Milk solids( kg ha‐１ yr‐１ ) １３ j.４３７ １７  .９２５ １３ .４３７Efficiency indices( kg N２O‐N tonne‐１ milk) ０ <.５７ ０ 种.４５ ０ 殚.５２Gain in efficiency ( ％ ) ２２  ９ 殚Conclusions The results confirm that the use of low‐N feed supplements or restricted grazing regimes during wet winter areeffective at reducing N２O emissions from dairy farms in terms of N２O emissions per unit of milk production .ReferencesClark H , Pinares‐Patino C , de Klein CAM ( ２００５ ) Methane and nitrous oxide emissions from grazed grasslands . In :McGilloway DA , Grassland : a global resource , Wageningen Academic Publishers , ２７９‐２９３ .Luo J , Ledgard SF , de Klein CAM , Lindsey SB , Kear M ( ２００８a) Effects of dairy farming intensification on nitrous oxideemissions . Plant and Soil , ( in press) .Luo J , Ledgard SF , Lindsey SB ( ２００８b) A test of a winter farm management option for mitigating nitrous oxide emissionsfrom a dairy farm . Soil Use and Management , ( in press) .3.0 y = 0.0197x + 0.3462 ♦ R2 = 0.5099 ♦ 2.5 :c 1: 2.0 z >< 1.5 ::, .::: ~ 1.0 ~ ♦ C) 0.5 0 ...J 0 0 20 30 40 50 60 70 80 90 100 WFPS (%) 

Nitrous Oxide Emissions from Dairy Pasture Systems in New Zealand

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Nitrous Oxide Emissions from Dairy Pasture Systems in New Zealand

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