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EFFECTS OF FERTILIZER ADDITION ON MICROBIAL RESPIRATION AND UPTAKE OF CARBON MONOXIDE IN A CERRADO SOIL
Citation:
MOLINA, M., R. G. ZEPP, A. KOZOVITS, J. BRESOLIN, AND M. BUSTAMANTE. EFFECTS OF FERTILIZER ADDITION ON MICROBIAL RESPIRATION AND UPTAKE OF CARBON MONOXIDE IN A CERRADO SOIL. Presented at LBA Science Meeting, Sao Paulo, BRAZIL, November 10 - 12, 2005.
Impact/Purpose:
The objective of the proposed study is to evaluate and apply fast and reproducible DNA-based technology that can detect and track fecal contamination back to its source in complex environmental matrices, including recreational and drinking water resources.
Description:
The savanna area in central Brazil (Cerrado) is undergoing rapid agricultural land use changes and these changes are often accompanied by fertilization of the land. Because fertilization is a widespread management practice in the Cerrado, it is important to understand the effect that such treatments have on the microbial decomposition rates of soil organic matter (SOM) of various qualities. We conducted laboratory incubation studies on the effects of added fertilizers on bacterial production of carbon dioxide (CO2) and consumption of carbon monoxide (CO) in soil samples obtained from native Cerrado areas (20-50% canopy cover). The effects of added fertilizers were investigated by comparing fluxes in controls with no added fertilizer and soils with added nitrogen (40 ?g/g of soil as (NH4)2SO4) and phosphorus (1 mg/g of soil as Ca(H2PO4)2+CaSO4?2H2O) in gas-tight jars maintaining the same soil moisture level throughout treatments. Soil respiration was analyzed assuming that the soil organic matter (SOM) could be described by a two-compartment model (labile and refractory SOM). Results indicate that during the first 10 days, respiration from the labile component of the SOM was enhanced by addition of both fertilizers. However, in longer-term incubations (>32 days) addition of phosphorus produced the largest enhancement in respiration from the more refractory SOM. CO was taken up by the soil cores in all cases and the uptake was quantified as deposition velocities. The deposition velocities were enhanced by the addition of fertilizer with particularly large effects observed with soil cores amended by phosphorus. Observed mean deposition velocities at 28 degrees C were: control 0.0059 cm s-1; with added N 0.0081 cm s-1; and with added P 0.010 cm s-1.