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REGIONAL EMISSIONS OF NITRIC OXIDE (NO) AND CARBON DIOXIDE (CO2) IN AGROECOSYSTEMS IN CENTRAL WEST REGION, BRAZIL.
Citation:
FERNANDES, E., M. BUSTAMANTE, A. KOZOVITS, AND R. G. ZEPP. REGIONAL EMISSIONS OF NITRIC OXIDE (NO) AND CARBON DIOXIDE (CO2) IN AGROECOSYSTEMS IN CENTRAL WEST REGION, BRAZIL. Presented at Large-Scale Biosphere-Atmosphere Eco Science Team Meeting and Synthesis Workshop, Salvador, BRAZIL, September 28 - 30, 2007.
Impact/Purpose:
The overall objective of this task is to develop quantitative relationships for assessing the vulnerability of aquatic ecosystems (freshwater and coastal) and their services to global change. The task will contribute experimental and modeling tools for assessments of the interactions of global climate and UV changes with coral reefs and selected watersheds and estuaries in the U.S. and Brazil These activities are contributing to two APGs in the ecosystems focus area of the Global Change Research Multiyear Plan: the 2008 APG (APG 2) on developing information and tools that managers will use in their decision-making about how to adapt to the effects of global change on aquatic ecosystems; and the 2010 APG (APG 3) on providing information and models that will support development of biocriteria for corals. One major task objective is to assess interactions of global warming and UV exposure that are contributing to the observed coral bleaching and disease. Our lab is working with scientists at the NHEERL Gulf Ecology Lab to characterize UV exposure and effects at several coral reef sites in the Florida Keys. This collaboration will contribute to one ERD APM in 2006 and three joint NERL-NHEERL APMs in the 2008 - 2010 period. Other research is examining the effects of changing climate and UV on microbial activity in waters close to beaches in the U.S. Work is being completed on the interactions of land use and climate changes with the ecological functioning of streams in watersheds of the southeastern U.S. The task also includes two sub-tasks that are funded mainly by funds-in IAGs. One sub-task funded by NASA involves research in central Brazil that is part of the Large Scale Biosphere Atmosphere Experiment (LBA). This work involves a close collaboration between EPA and a group of scientists from the Department of Ecology, University of Brasilia, Brazil. The objectives of this project are to assess the impacts of land use and climatic changes on soil nutrient cycles and microbiota, trace gas exchange and water quality in the Brazilian cerrado. Another sub-task funded by the Office of Naval Research is examining interactions between nitrogen and organic substances in aquatic ecosystems that produce the colored dissolved organic matter (CDOM) that controls penetration of solar UV radiation into coastal waters.
Description:
The Central West Region in Brazil has been the focus of intense agricultural expansion since the 1970s and, nowadays, a large area of native cerrado has been converted to agricultural use. The expansion was accompanied by intensive use of fertilizer, irrigation and management practices. However, the consequences of these agricultural practices on NO and CO2 emissions from soil to atmosphere are still unclear. Here, we present estimates of regional emissions of NO and CO2 in a Latosol cultivated with corn, soybean, cotton and irrigated bean, under a no till system. The measurements were made from August, 2003 to August, 2005. NO and CO2 fluxes were measured before and after planting, after nitrogen fertilization, during the growing season and before and after harvesting. The regional emissions were estimated considering the area occupied by the crops and the cropping cycle (corn 173, soybeans 134, cotton 258 and irrigated beans 135 days). The field cotton had the highest N-NO emission per unit area (0.8 kg ha-1), followed by irrigated beans and corn (0.3 kg ha-1) and soybeans (0.2 kg ha-1). Per hectare, the field cotton and corn contributed 34.6 and 32.0 tons C-CO2, the irrigated beans 25,4 tons and the soybeans 19.4 tons C-CO2. Integrated over all cultivated fields, the highest soil emissions of NO and CO2 came from soybeans which emitted 4.6 Gt N-NO and 0.12 Tg C-CO2 from 22,854,000 ha, followed by corn with 3.7 Gt N-NO and 0.11 Tg C-CO2 from 12,297,000 ha, irrigated beans with 1.2 Gt N-NO and 0.03 Tg C-CO2 from 3,910,000 ha, and cotton with 0.9 Gt N-NO and 0.01 Tg C-CO2 from 1,152,000 ha. The results show that it is necessary for government policies to encourage management systems that enhance sustainability and that take into account the impacts of agricultural activities on soil emissions of NO and CO2.