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Field Measurement of Denitrification: I. Flux of N 2 and N 2 O
Author(s) -
Rolston D. E.,
Hoffman D. L.,
Toy D. W.
Publication year - 1978
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/sssaj1978.03615995004200060004x
Subject(s) - loam , denitrification , environmental science , manure , flux (metallurgy) , soil water , irrigation , nitrogen , fertilizer , soil horizon , water content , hydrology (agriculture) , soil science , chemistry , agronomy , geology , geotechnical engineering , organic chemistry , biology
Absolute amounts and rates of denitrification from a Yolo loam (Typic Xerorthents) field profile were studied in relation to the influence of soil‐water content, organic C source, and soil temperature. Field plots were intensely instrumented with soil atmosphere samplers, tensiometers, and thermocouples. Soil‐water contents were maintained constant with a spray irrigation system activated at frequent time intervals. The upper 15 cm of soil was maintained at soil‐water pressure heads ( h ) of −15 and −70 cm of water for the two different water regimes of the experiment conducted at a soil temperature (5 cm depth) of 23°C. Soil‐water pressure heads were maintained at −8 and −50 cm for the two water regimes conducted at 8°C. Plots cropped with ryegrass, uncropped plots, and plots to which manure was mixed in the top 10 cm of soil were used to establish three different C levels. Fertilizer was applied at the rate of 300 kg N ha −1 as KNO 3 enriched with 20 and 40% 15 N for the h = −15 or −8 and h = −70 or −50 cm treatments, respectively. The flux of gases at the soil surface was measured from the accumulation of N 2 O and 15 N 2 beneath an air‐tight cover placed over the soil surface for 1 or 2 hours per day. Denitrification from gas fluxes occurred for the 23°C experiment in order of decreasing magnitude in manure ( h = −15 cm), manure ( h = −70 cm), cropped ( h = −15 cm), cropped ( h = −70 cm), uncropped ( h = −15 cm), and uncropped ( h = −70 cm) plots. Approximately 70% of the fertilizer N was denitrified for the manure ( h = −15 cm) treatment. Approximately 1% of the added fertilizer was denitrified in the uncropped ( h = −70 cm) treatment. Denitrification from gas fluxes for the 8°C experiment occurred in the same order as that of the 23°C experiment except that rates and absolute magnitudes were much smaller. Approximately 11% of the fertilizer N was denitrified for the manure ( h = −8 cm), and no measurable denitrification occurred in the uncropped ( h = −50 cm) treatment. The amount of N 2 produced was much greater than N 2 O for all plots. The N 2 O flux at the soil surface was dependent upon time and degree of anoxic development and varied between 5 and 26% of total denitrification.