Soil-atmosphere N 2 O exchange in natural savannah, non-fertilized and fertilized agricultural land in Burkina Faso (W. Africa)

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1 Forschungszentrum Krlsruhe in der Helmholtz-Gemeinschft Institut für Meteorologie und Klimforschung Atmosphärische Umweltforschung (IMK-IFU), Grmisch-Prtenkirchen Soil-tmosphere N 2 O exchnge in nturl svnnh, non-fertilized nd fertilized griculturl lnd in Burkin Fso (W. Afric) Brüggemnn N, Brümmer C, Butterbch-Bhl K, Wssmnn R, Ppen H Forschungszentrum Krlsruhe Institute for Meteorology nd Climte Reserch Atmospheric Environmentl Reserch (IMK-IFU) Kreuzeckbhnstrße Grmisch-Prtenkirchen, Germny N. Brüggemnn et l. 4 th Nitrogen Conference, Cost do Suipe October 1-5, 27 IMK-IFU Grmisch-Prtenkirchen

2 Loction of study re Ougdougou Bontioli Dno Burkin Fso Climte Men nnul ir temperture: 29.5 C Men nnul precipittion: 926 mm Riny seson: My to October N. Brüggemnn et l. 4 th Nitrogen Conference, Cost do Suipe October 1-5, 27 IMK-IFU Grmisch-Prtenkirchen

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13 Bontioli Field sites Dno Nturl svnnh - dry Nturl svnnh - wet Bontioli Reserve nture prk, no frming, no tillge, no livestock Sorghum Dno Cotton Dno used for griculture since severl decdes used for griculture since 15 yers Sorghum Bontioli Penut Dno N. Brüggemnn et l. 4 th Nitrogen Conference, Cost do Suipe October 1-5, 27 IMK-IFU Grmisch-Prtenkirchen

14 Site chrcteristcs I Bontioli Reserve II Sorghum Bontioli III Sorghum Dno IV Cotton Dno V Penut Dno Loction Altitude [m.s.l.] Slope [ ] 1 51' 55.8'' N 3 4' 21.5'' W 293 <1 1 52' 18.1'' N 3 3' 59.'' W 295 <1 11 9' 52.9'' N 3 5' 3.'' W ' 53.2'' N 3 5' 1.4'' W ' 53.6'' N 3 5' 2.7'' W Mngement Nturl reserve, no frming, no tillge Agriculture since 15 yers Agriculture since severl decdes Agriculture since severl decdes Agriculture since severl decdes Smpling Frequency 1-3 week week week -1 / 1 d week week -1 Bulk density [g cm -3 ] ph C:N rtio C org [%] N totl [%] 1.43 ± ± ± ±.6.5 ± ±.1 6. ± ± ±.4.6 ± ± ± ±.3.86 ±.12.7 ± ± ± ± ±.9.7 ± ± ± ± ±.11.7 ±.1 Soil texture snd [%] silt [%] cly [%] Stone frction [%] sndy lom lomy snd lom lom lom Agriculturl prctice Seeds sown in My, no fertilizer ppliction (except fertilizer experiment), topsoil erted with hoes every 2 to 4 weeks fter sowing, hrvest in October. N. Brüggemnn et l. 4 th Nitrogen Conference, Cost do Suipe October 1-5, 27 IMK-IFU Grmisch-Prtenkirchen

15 Experiments Experiment A N 2 O fluxes from nturl svnnh nd sorghum in Bontioli, nd from sorghum, cotton & penut in Dno using mnul chmber smpling 1-3 times per week in 25 nd 26 Experiment B Effect of NPK-fertilizer ddition to 3 plots of sorghum field in Dno (plot A: 14 kg N h -1 ; plot B: 52.5 kg N h -1 ; plot C: control) on N 2 O fluxes using utomted chmber smpling over severl weeks in 26 Experiment C Lbortory study on potentil N 2 O efflux from soils of the Bontioli nturl svnnh nd Bontioli sorghum under different soil moisture conditions N. Brüggemnn et l. 4 th Nitrogen Conference, Cost do Suipe October 1-5, 27 IMK-IFU Grmisch-Prtenkirchen

16 Mnul nd utomted chmber mesurements Mnul: 4 chmbers t ech site, mesured 1-3 times per week Smpling with syringes in the field Pneumticlly operted chmbers Automted: 3 chmbers t ech plot, mesured continuously (1 vlues per dy) GC nlysis t the sme dy On-line GC nlysis in the field N. Brüggemnn et l. 4 th Nitrogen Conference, Cost do Suipe October 1-5, 27 IMK-IFU Grmisch-Prtenkirchen

17 No fertiliztion, mnul mesurements ir temp. [ C] soil temp. [ C] N 2 O flux WFPS [%] [µg N 2 O-N m -2 h -1 ] 1 Jun 1 Jul 1 Aug 1 Sep 1 Apr 1 Jun 1 Aug 1 Oct Jun 1 Jul 1 Aug 1 Sep Apr 1 Jun 1 Aug 1 Oct 26 precip. [mm d -1 ] WFPS [%] N 2 O flux [µg N 2 O-N m -2 h -1 ] ir temperture soil temperture Bontioli Reserve Sorghum Bontioli Sorghum Dno Cotton Dno Penut Dno Brümmer et l., Ecosystems, submitted N. Brüggemnn et l. 4 th Nitrogen Conference, Cost do Suipe October 1-5, 27 IMK-IFU Grmisch-Prtenkirchen

18 No fertiliztion, mnul mesurements men fluxes [µg N 2 O-N m -2 h -1 ] A bc Bontioli Reserve A B Sorghum Bontioli A bc Sorghum Dno A B Cotton Dno ba A Penut Dno [µg N 2 O-N m -2 h -1 ] n = , ± SE; lowercse letters = significnt differences (p <.5) between yers; uppercse letters = between sites Brümmer et l., Ecosystems, submitted N. Brüggemnn et l. 4 th Nitrogen Conference, Cost do Suipe October 1-5, 27 IMK-IFU Grmisch-Prtenkirchen

19 Fertiliztion, utomted mesurements soil temperture [ C] WFPS [%] precipittion [mm] precipittion soil temperture soil moisture Plot A - high N-fertliser ddition (14 kg per h) Plot B - ordinry N-fertiliser ddition (52.5 kg per h) Plot C - no N-fertiliser ddition plot A [14 kg N h -1 ] plot B [52.5 kg N h -1 ] 1 N 2 O flux [µg N 2 O-N m -2 h -1 ] fertiliztion N 2 O flux [µg N 2 O-N m -2 h -1 ] plot A: y = * e.7x R 2 =.9 plot B: y = * e.2x R 2 = Brümmer et l., Ecosystems, submitted dys fter fertilistion N. Brüggemnn et l. 4 th Nitrogen Conference, Cost do Suipe October 1-5, 27 IMK-IFU Grmisch-Prtenkirchen

20 No fertiliztion, diurnl cycles of N 2 O fluxes Men diurnl N 2 O fluxes t the unfertilized Sorghum field in Dno from June 26 to August 17, 26 (n = 42, ± SE). 7 : 4: 8: 12: 16: 2: 24: N 2 O flux [µg N 2 O-N m -2 h -1 ] : 4: 8: 12: 16: 2: 24: time of the dy Brümmer et l., Ecosystems, submitted N. Brüggemnn et l. 4 th Nitrogen Conference, Cost do Suipe October 1-5, 27 IMK-IFU Grmisch-Prtenkirchen

21 Effect of single nd repeted wtering on N 2 O fluxes N 2 O flux [µg N 2 O-N m -2 h -1 ] N 2 O flux [µg N 2 O-N m -2 h -1 ] A C wetting c wetting soil moisture - dry up b soil moisture - dry up Time since wetting [d] N 2 O flux Bontioli Reserve N 2 O flux Bontioli Sorghum b B D b c b soil moisture - constnt b wetting soil moisture - constnt wetting Time since wetting [d] soil moisture Bontioli Reserve soil moisture Bontioli Sorghum b % WHC mx % WHC mx Medium wter content High wter content (n = 3, ± SE) Brümmer et l., Ecosystems, subm. N. Brüggemnn et l. 4 th Nitrogen Conference, Cost do Suipe October 1-5, 27 IMK-IFU Grmisch-Prtenkirchen

22 Conclusions Very low N 2 O emission rtes from rin-fed nd non-fertilized griculturl fields during both wet nd dry seson No significnt differences in N 2 O exchnge between the most typicl crops of Burkin Fso, i.e. sorghum, cotton, nd penut in 25, however in 26 N 2 O emissions from nturl svnnh site in 25 slightly, but not significntly higher thn from the griculturl fields, in 26 significntly higher No significnt difference of time of conversion of svnnh to griculture on N 2 O emissions Appliction of N fertilizer led to grdul, but significnt increse of N 2 O emissions N 2 O emissions were highest t medium soil wter content, especilly fter single wetting events with subsequent dry up N. Brüggemnn et l. 4 th Nitrogen Conference, Cost do Suipe October 1-5, 27 IMK-IFU Grmisch-Prtenkirchen

23 Thnk you, nd mny thnks lso to the tem! Funding for this reserch work ws provided by the Helmholtz Assocition of Germn Reserch Centres (Virtul Institute, VH-VI-1). N. Brüggemnn et l. 4 th Nitrogen Conference, Cost do Suipe October 1-5, 27 IMK-IFU Grmisch-Prtenkirchen