Co-denitrification: an important nitrogen cycling process in grazed grasslands

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C-denitrificatin: an imprtant nitrgen cycling prcess in grazed grasslands D.R. Selbie 1,2,3, G.J. Lanigan 1, R.J. Laughlin 4, H.J. Di 3, James L. Mir 3, K.C. Camern 3, T.J. Clugh 3, C.J. Watsn 4, J.

1 C-denitrificatin: an imprtant nitrgen cycling prcess in grazed grasslands D.R. Selbie 1,2,3, G.J. Lanigan 1, R.J. Laughlin 4, H.J. Di 3, James L. Mir 3, K.C. Camern 3, T.J. Clugh 3, C.J. Watsn 4, J. Grant 1, C. Smers 1 & Karl G. Richards 1 1 Teagasc, Envirnmental Research Centre, Jhnstwn Castle, Wexfrd, Ireland. 2 Centre fr Sil & Envirnmental Research, Lincln University, Christchurch, New Zealand 3 AgResearch, Ruakura Research Centre, Hamiltn, New Zealand 4 Agri-Envirnment Branch, Agri-Fd & Bisciences Institute, Belfast BT9 5PX, UK.

2 Backgrund 60-90% ingested N returned in excreta Gaseus emissin NH 3, N 2 O, N 2 Pasture uptake Leaching Urine patch lading rate g N/m 2

3 Backgrund 2 Cnceptual mdel f c-denitrificatin under urine patches in grassland sils, cmmencing with urea, the dminant N substrate fund in ruminant urine.

4 OBJECTIVES 1. Quantify lss f N 2 frm urine amended sils 2. Quantify the cntributin f cnventinal denitrificatin and c-denitrificatin t N 2 lsses

10 g N/L = 100 (+DCD) 2 L urine applied t 0.2 m 2 Nitrificatin inhibitr DCD applied (1.

5 METHODS - treatments Urine cllected frm dairy cws during milking Urine was amended with 15 N urea t enrich the N cntent t 45 atm% excess Tw treatments g N m -2 Urine 10 g N/L = 100 Urine 10 g N/L = 100 (+DCD) 2 L urine applied t 0.2 m 2 Nitrificatin inhibitr DCD applied (1.5 g m -2 ) in slutin frm day after urine (late autumn), again in late winter (annual 3.0 g m -2 DCD)

METHODS N 2 O + N 2 emissins Static clsed chamber Gas

cntributin due t cdenitrificatin (N 2CO ) and true

6 METHODS N 2 O + N 2 emissins Static clsed chamber Gas chrmatgraphy (N 2 O) IRMS N 2 O & N 2 Stable Istpe Labratry, UC Davis Calculatins The flux f N 2 was calculated using Δ 29 R and Δ 30 R t calculate cntributin due t cdenitrificatin (N 2CO ) and true denitrificatin (N 2TRUE ). Stats methds Effect f DCD n cumulative emissins (date)

7 Calculating C-denitrificatin 1 Labelled 15 N 2 (50 atm%) true denitrificatin C-denitrificatin 15N 15N D 30 R 15N 14N D 29 R 15N 14N D 29 R T calculate c-denitrificatin flux need t measure the D 29 R and D 30 R beam areas and subtract ut the 29 N 2 arising frm true denitrificatin The fractin f the ttal mles f N 2 in the headspace frm c-denitrificatin (dcd) is. d CD = -D 29 Rp 12 /(-D 29 Rp 12 +D 29 Rp 1 p 2 +q 1 p 2 -q 2 p 1 ) p 1 (0.9963) and q 1 (0.0037) are atm fractins f 14 N and 15 N in the natural abundance pl p 2 and q 2 are the atm fractins f 14 N and 15 N in the enriched pl 1 Stevens RJ & Laughlin RJ 2001 Sil Bilgy & Bichemistry

8 RESULTS Tempral emissins N 2 O TRUE DENITRIFICATION Selbie et al. (2015) Nature Scientific Reprts 5:

9 RESULTS Tempral emissins N 2 TRUE DENITRIFICATION Selbie et al. (2015) Nature Scientific Reprts 5:

10 RESULTS Tempral emissins N 2 CO-DENITRIFICATION Selbie et al. (2015) Nature Scientific Reprts 5:

11 RESULTS Effect f Nitrificatin (30 days pst urine) P < 0.05 Selbie et al. (2015) Nature Scientific Reprts 5:

12 RESULTS Cumulative Gaseus Emissins N 2CO 55.8 g N m -2 N 2TRUE 1.07 g N m -2 N 2 O TRUE 0.66 g N m -2 Selbie et al. (2015) Nature Scientific Reprts 5:

13 CONCLUSIONS N lsses t air via N 2 was the dminant lss pathway frm urine amended sil (majr lss pathway) 56.9 g N m -2 C-denitrificatin accunted fr 55.8 g N m -2, cmpared t nly 1.1 g N m -2 frm True Denitrificatin (cnventinal methds underestimate ttal N 2 lss) C-denitrificatin was the main surce f N 2 (98% f ttal). Drivers require further investigatin. Large c-denitrificatin N 2 lss suggest large lsses f native sil N. High emissins f N 2 and lss f rganic sil N helps explain lw N recveries in grazed grassland

14 Acknwledgements This research is financially supprted under the Natinal Develpment Plan, thrugh the Research Stimulus Fund (07 536), administered by the Department f Agriculture, Fd and the Marine, Ireland and the Teagasc Walsh Fellwship Scheme

15 References ISOTOPIC MIXING MODEL CALCULATIONS Mulvaney RL & Bast CW (1986) Equatins fr determinatin f N-15 labelled dinitrgen and nitrus-xide by mass-spectrmetry. Sil Science Sciety f America Jurnal 50(2): EQUATION TO CALCULATE ENRICHMENT OF DENITRIFYING POOL FROM A SINGLE POOL SOURCE Arah JRM (1997) Apprtining nitrus xide fluxes between nitrificatin and denitrificatin using gas-phase mass spectrmetry. Sil Bilgy & Bichemistry 29(8): CALCULATING DENITRIFYING POOL ENRICHMENT FROM TWO-SOURCE POOL Stevens RJ & Laughlin RJ (2001) Lwering the detectin limit fr dinitrgen using the enrichment f nitrus xide. Sil Bilgy & Bichemistry 33(9): Further questins: karl.richards@teagasc.ie

16 Calculating C-denitrificatin The surces f N 2 are apprtined int the fractin f gas (d' D ) derived frm the denitrifying pl f enrichment ad and the fractin d' N = (1 - d' D ) derived frm the pl r pls at natural abundance Headspace N 2 istpic signature reflects the relative cntributin f ad, an and atm N2 Labelled pl ad Atm N 2 Natural abundance pl an Utilising D 29 R and D 30 R, we can calculate full N 2 flux using istpic mixing mdels (Mulvaney & Bast 1986) which assume that 14N and 15N atms are randmly Distributed during N 2 generatin Can calculate true denitrificatin frm D 30 R assume that that there is nly a labelled pl and atm N 2 cntributing t the enrichment f the denitrifying pl Using the backslver t estimate the value f D 29 R that culd be attributed t true denitrificatin The remaining D 29 R is surced frm c-denitrificatin

17 Nitrificatin Inhibitrs DCD NH 4 + Catin exchange NO 3 - The Nitrgen Cycle (McLaren & Camern, 1996)

18 METHODS - Trial establishment A (0-15 cm) A-B (15-55 cm) Intact mnlith lysimeters Haplic Cambisl (WRB, 2007) Imprtant dairy farming sil Free-draining sandy lam Ryegrass pasture 30 lysimeters cllected and installed at Jhnstwn Castle, Wexfrd 2009 B ( cm)

UC A-G Chemistry. Gorman Learning Center (052344) Basic Course Information

UC A-G Chemistry. Gorman Learning Center (052344) Basic Course Information UC A-G Chemistry Grman Learning Center (052344) Basic Curse Infrmatin Title: UC A-G Chemistry Transcript abbreviatins: A-G Chem / A-G Chem Length f curse: Full Year Subject area: Labratry Science ("d")