Trace Gas Emissions From the Soil Related to Land-Use Changes in the Cerrado Region
Alessandra
Rodrigues
Kozovits, Universidade de Brasília, kozovits@unb.br
(Presenting)
Laura
Tillman
Viana, Universidade de Brasília, lviana@unb.br
Danielle
Matias
Sousa, Universidade de Brasília, daniellematias@yahoo.com.br
Mercedes
Maria Cunha
Bustamante, Universidade de Brasília, mercedes@unb.br
Richard
Zepp, Environmental Protection Agency, zepp.richard@epamail.epa.gov
The conversion of native Cerrado areas (savannas of central Brazil) into croplands, may change the magnitude and dynamics of soil trace gases emissions. We measured NO, N2O and CO2 fluxes, soil moisture, available inorganic N and net mineralization rate in areas planted with corn, soybean and common bean and in adjacent native Cerrado areas. These crops are the most important in the region. Data collection followed the crop management (just before and after each fertilization) and also monthly during the growth season. The study has been conducted at the Fazenda Dom Bosco, about 100 Km from Brasília. Higher NO soil emissions were found in the corn (up to 9.44 ng NO cm-2 h-1) and bean (up to 8.87 ng NO cm-2 h-1) areas compared to native Cerrado and soybean areas (1.08 and 0.67 ng NO cm-2 h-1, respectively) and accompanying the status of available N in the soil. The net N mineralization and net nitrification dynamics were similar in the two legume crops, with immobilisation before the plantation and mineralization just after the sowing. In the native area, there was net mineralization during the dry season and immobilisation with the onset of the rain season. Generally, N2O was under the detection limit (0.6 ng N2O cm-2 h-1). Higher values were observed in the cornfield just after N fertilization (1.84 ng N2O cm-2 h-1). In contrast to the N emissions, soil respiration from all studied sites seemed to be closely related to the soil moisture, tending to be higher in the crop areas (2.81 to 6.41 µmolCO2 m-2 s-1). The results indicate a clearly increase in the NO emissions with the replacement of native Cerrado areas by fertilized crops. Emissions from the soybean area were similar to the native Cerrado although post-harvest measurements were still not taken.