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Denitrification Measured Directly from Nitrogen and Nitrous Oxide Gas Fluxes
Author(s) -
Rolston D. E.,
Fried M.,
Goldhamer D. A.
Publication year - 1976
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1976.03615995004000020020x
Subject(s) - denitrification , nitrous oxide , leaching (pedology) , soil water , nitrogen , lolium perenne , chemistry , soil science , nitrate , environmental science , hydrology (agriculture) , environmental chemistry , perennial plant , agronomy , geology , geotechnical engineering , organic chemistry , biology
The amount of denitrification is generally the unknown in attempts to evaluate the fate of N fertilizers applied to soils. Substantial error can result when denitrification is determined from the difference between measurements of plant uptake, residual soil N, leaching, and the amount of N applied. An independent, direct measure of denitrification potentially has merit by containing only the error from direct measurement and not a cumulative error from several measurements. Nitrate at a rate of 300 kg of N/ha and enriched with 20 and 10 atom percent excess 15 N was applied to laboratory columns and a field plot, respectively. The columns were maintained at soil‐water pressure heads of −22 and −70 cm. The field plot was maintained at a soil‐water pressure head of approximately −10 cm in the upper 10 cm of soil. The field plot was cropped with perennial ryegrass (Lolium perenne) . The columns and field plot were instrumented with tensiometers, soil solution samplers, and gas samplers. The concentration and isotopic ratio of NO 3 , N 2 , and N 2 O were measured as a function of soil depth and time. The gaseous concentration gradients and measured apparent diffusion coefficients were used to calculate the fluxes of 15 N 2 and 15 N 2 O gas from the soil. Residual soil N, plant uptake, and leaching were measured in order to calculate denitrification by difference. For the laboratory columns, the amount of denitrification determined directly compared favorably with that determined by difference. For the field plot, the disparity between denitrification calculated directly and by difference was attributable to the uncertainty in the gaseous concentration gradient near the soil surface and the spatial variability of the apparent diffusion coefficient near water saturation.