HR: 16:00h
AN: B54A-01    [Abstracts]
TI: Nitrogen Losses as N2O and NO After Non-tillage Agricultural Practice in a Tropical Corn Field at Guarico State, Venezuela.
AU: * Perez, T J
EM: tperez@ivic.ve
AF: Instituto Venezolano de Investigaciones Cientificas, Atmospheric Chemistry Lab. IVIC Aptdo 21827, Caracas, 1020A Venezuela
AU: Gil, J A
EM: jenieg@pdvsa.com
AF: Instituto Venezolano de Investigaciones Cientificas, Atmospheric Chemistry Lab. IVIC Aptdo 21827, Caracas, 1020A Venezuela
AU: Marquina, S
EM: smarquina@ivic.ve
AF: Instituto Venezolano de Investigaciones Cientificas, Atmospheric Chemistry Lab. IVIC Aptdo 21827, Caracas, 1020A Venezuela
AU: Donoso, L E
EM: edonoso@ivic.ve
AF: Instituto Venezolano de Investigaciones Cientificas, Atmospheric Chemistry Lab. IVIC Aptdo 21827, Caracas, 1020A Venezuela
AU: Trumbore, S E
EM: setrumbo@uci.edu
AF: University of California Irvine, Dept. Of Earth System Science. University of California, Irvine, CA 92697 United States
AU: Tyler, S C
EM: styler@uci.edu
AF: University of California Irvine, Dept. Of Earth System Science. University of California, Irvine, CA 92697 United States
AB: Historically, the most common agricultural practice in Northern Guárico, one of Venezuelan largest cereal production regions, has been mono cropping, with extensive tillage operations that usually causes rapid soil degradation and nitrogen losses. Alternative production systems, such as non-tillage agricultural practices, have been extensively implemented during the last few years. However, studies of the nitrogen losses associated with these alternative practices are not widely available. This study was conducted at "Fundo Tierra Nueva", Guárico State (9°23'33" N, 66° 38'30" W) in a corn field under the non-tillage agricultural practice, during the growing season June-August 2005. The soils are Vertisols (Typic Haplusterts). The area has two well defined precipitation seasons: wet (May-October) and dry (November-April). The mean annual precipitation of the area is 622±97.3 mm (last 5 years). Because the irrigation of the crop depends on precipitation, the planting is scheduled during the months of highest precipitation in June-July. We measured nitrogenous gas emissions (N₂O and NO), concentrations of total nitrogen (NT), NH₄⁺ and NO₃^- in soil (0-100 cm) after fertilization to estimate the nitrogen losses. We also measured CO₂ emissions to evaluate the relationship of microbial respiration to the emissions of nitrogenous trace gases. Soils were fertilized with 54 kgN/ha (NPK 12:24:12, nitrogen as NH₄Cl) and planted simultaneously by a planting machine provided with a furrow opener where the fertilizer and seeds are incorporated between 0-10 cm depth. Thirty days later, soils were fertilized by broadcast addition of 18 kgN/ha (as ammonium nitrate). Nitrous oxide emissions were highly dependant on the water content. Prior to fertilization N₂O emissions were very low. Right after fertilization the emissions increased by a factor of 5 compared to pre-fertilization levels and increased to 100 times larger after the first heavy rain. NO emissions did not increase as much as N₂O emissions after the first fertilization. Right after the second fertilization both gases increased their emissions and concentrations in soil profile dramatically. These results suggest that broadcast fertilizer addition with ammonium nitrate stimulates the nitrogenous gas emissions due to enhanced nitrification and denitrification at the soil surface. Estimates of percentage of nitrogen losses and fertilizer-induced emission factors (FEI) for both gases are provided.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0402 Agricultural systems
DE: 0469 Nitrogen cycling
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
DE: 4845 Nutrients and nutrient cycling (0470, 1050)
SC: Biogeosciences [B]
MN: Fall Meeting 2005