A Look at Amazon Basin Seasonal Dynamics with the Biophysical ...
A Look at Amazon Basin Seasonal Dynamics with the Biophysical ... A Look at Amazon Basin Seasonal Dynamics with the Biophysical ...
Control of N 2 O and N 2 Emissions from Amazonian Pastures Under Intensified Use:Availability of Nitrogen, Carbon and the Effects of Soil TillageChristopher Neill 1 , Paul A. Steudler 1 , and Marisa C. Piccolo 21. The Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA 02543, USAcneill@mbl.edu2. Centro de Energia Nuclear na Agricultura, Avenida Centenário, 303, Caixa Postal 96,CEP 13416000, Piracicaba, SP, BrazilGrowing intensification of existing pastures in the Amazon has the potential toincrease emissions of nitrogen gases from soil. We tested the effects of soil moisture andnitrogen and carbon availability on the production of N 2 O and the distribution of N 2 O andN 2 production in laboratory incubations. We also compared non-tilled and recently-tilledpasture soils to determine how tillage alters nitrogen and carbon availability as controlsof gaseous N production. Non-tilled soils at low soil moisture and soils brought tosaturation with deionized water or deionized water plus carbon produced little N 2 O. Incontrast, non-tilled soil amended with both deionized water and nitrate produced highamounts of both N 2 O and N 2 from denitrification at soil water filled pore space above80%. Ammonia additions to saturated soil stimulated N 2 O production after a short lag,indicating that nitrate to support denitrification was quickly produced by nitrification.These results indicated that the combination of absence of anaerobic conditions andnitrate strongly limited N 2 O production from non-tilled pasture soils, but that thepresence of available carbon did not. Tilling led to higher N 2 O production and this effectwas caused by both higher N and higher C availability in tilled soils. Currently, the soilsof non-tilled, unfertilized Amazonian pastures produce relatively low amounts of N 2 O.These soils appear poised to produce large amounts of N 2 O under tillage coupled withfertilization if the elevated concentrations of N from fertilizer application are presentduring periods when soil moisture exceeds 70 to 80% water filled pore space.
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Control of N 2 O and N 2 Emissions from <strong>Amazon</strong>ian Pastures Under Intensified Use:Availability of Nitrogen, Carbon and <strong>the</strong> Effects of Soil TillageChristopher Neill 1 , Paul A. Steudler 1 , and Marisa C. Piccolo 21. The Ecosystems Center, Marine Biological Labor<strong>at</strong>ory, Woods Hole, MA 02543, USAcneill@mbl.edu2. Centro de Energia Nuclear na Agricultura, Avenida Centenário, 303, Caixa Postal 96,CEP 13416000, Piracicaba, SP, BrazilGrowing intensific<strong>at</strong>ion of existing pastures in <strong>the</strong> <strong>Amazon</strong> has <strong>the</strong> potential toincrease emissions of nitrogen gases from soil. We tested <strong>the</strong> effects of soil moisture andnitrogen and carbon availability on <strong>the</strong> production of N 2 O and <strong>the</strong> distribution of N 2 O andN 2 production in labor<strong>at</strong>ory incub<strong>at</strong>ions. We also compared non-tilled and recently-tilledpasture soils to determine how tillage alters nitrogen and carbon availability as controlsof gaseous N production. Non-tilled soils <strong>at</strong> low soil moisture and soils brought tos<strong>at</strong>ur<strong>at</strong>ion <strong>with</strong> deionized w<strong>at</strong>er or deionized w<strong>at</strong>er plus carbon produced little N 2 O. Incontrast, non-tilled soil amended <strong>with</strong> both deionized w<strong>at</strong>er and nitr<strong>at</strong>e produced highamounts of both N 2 O and N 2 from denitrific<strong>at</strong>ion <strong>at</strong> soil w<strong>at</strong>er filled pore space above80%. Ammonia additions to s<strong>at</strong>ur<strong>at</strong>ed soil stimul<strong>at</strong>ed N 2 O production after a short lag,indic<strong>at</strong>ing th<strong>at</strong> nitr<strong>at</strong>e to support denitrific<strong>at</strong>ion was quickly produced by nitrific<strong>at</strong>ion.These results indic<strong>at</strong>ed th<strong>at</strong> <strong>the</strong> combin<strong>at</strong>ion of absence of anaerobic conditions andnitr<strong>at</strong>e strongly limited N 2 O production from non-tilled pasture soils, but th<strong>at</strong> <strong>the</strong>presence of available carbon did not. Tilling led to higher N 2 O production and this effectwas caused by both higher N and higher C availability in tilled soils. Currently, <strong>the</strong> soilsof non-tilled, unfertilized <strong>Amazon</strong>ian pastures produce rel<strong>at</strong>ively low amounts of N 2 O.These soils appear poised to produce large amounts of N 2 O under tillage coupled <strong>with</strong>fertiliz<strong>at</strong>ion if <strong>the</strong> elev<strong>at</strong>ed concentr<strong>at</strong>ions of N from fertilizer applic<strong>at</strong>ion are presentduring periods when soil moisture exceeds 70 to 80% w<strong>at</strong>er filled pore space.
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