Open AccessNitrous Oxide Fluxes from Cultivated Areas and Rangeland: U.S. High Plains
Author(s) -
Weeks Edwin P.,
McMahon Peter B.
Publication year - 2007
Publication title -
vadose zone journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.036
H-Index - 81
ISSN - 1539-1663
DOI - 10.2136/vzj2006.0164
Subject(s) - vadose zone , flux (metallurgy) , nitrous oxide , dns root zone , soil water , environmental science , trace gas , atmosphere (unit) , hydrology (agriculture) , grassland , atmospheric sciences , chemistry , soil science , agronomy , geology , biology , geography , geotechnical engineering , organic chemistry , meteorology
Concentration profiles of N 2 O, a greenhouse gas, and the conservative trace gases SF 6 and the chlorofluorocarbons CFC‐11, CFC‐12, CFC‐113, and were measured periodically through thick vadose zones at nine sites in the U.S. High Plains. The CFC and SF 6 measurements were used to calibrate a one‐dimensional gas diffusion model, using the parameter identification program UCODE. The calibrated model was used with N 2 O measurements to estimate average annual N 2 O flux from both the root zone and the deep vadose zone to the atmosphere. Estimates of root‐zone N 2 O fluxes from three rangeland sites ranged from near 0 to about 0.2 kg N 2 O‐N ha −1 yr −1 , values near the low end of the ranges determined for native grass from other studies. Estimates of root‐zone N 2 O fluxes from two fields planted to corn ( Zea mays L.) of about 2 to 6 kg N 2 O‐N ha −1 yr −1 are similar to those determined for corn in other studies. Estimates of N 2 O flux from Conservation Reserve grassland converted from irrigated corn indicate that production of N 2 O is substantially reduced following conversion from cropland. Small N 2 O fluxes from the water table or from deep in the vadose zone occurred at three sites, ranging from 0.004 to 0.02 kg N 2 O‐N ha −1 yr −1 . Our estimates of N 2 O flux represent space‐ and time‐averaged values that should be useful to more fully evaluate the significance of instantaneous point flux measurements.