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Denitrification and Nitrous Oxide Emissions in Annual Croplands, Perennial Grass Buffers, and Restored Perennial Grasslands
Author(s) -
Iqbal Javed,
Parkin Timothy B.,
Helmers Matthew J.,
Zhou Xiaobo,
Castellano Michael J.
Publication year - 2014
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/sssaj2014.05.0221
Subject(s) - perennial plant , nitrous oxide , environmental science , grassland , denitrification , agronomy , greenhouse gas , nitrogen , agroforestry , chemistry , ecology , biology , organic chemistry
Inclusion of perennial vegetation filter strips (PFSs) in the toeslope of annual cropland watersheds can decrease NO 3 − –N losses to ground and surface waters. Although PFSs are similar to riparian buffers, the processes responsible for NO 3 − –N removal from PFSs are not well understood. Our objectives were to (i) determine the importance of denitrification as a sink for NO 3 − –N loss from PFSs and (ii) evaluate how PFSs alter the biophysical processes that affect the relative importance of N 2 O and N 2 emissions. To address our objectives, we used a coupled field laboratory approach with experimental watersheds that included the following treatments: (i) PFSs covering the bottom 10% of the watershed and an annual corn–soybean crop rotation covering the remaining upslope 90% (PFS); (ii) 100% corn–soybean rotation (CORN); and (iii) 19‐yr‐old 100% restored native grassland (RNG). In situ N 2 O flux rates and laboratory N 2 O/(N 2 + N 2 O) ratios were highest in CORN watersheds followed by PFS and RNG watersheds. In contrast, potentially mineralizable C and denitrification enzyme activity (DEA) were highest in PFS and RNG watersheds and lowest in CORN watersheds. Furthermore, there was a negative correlation between N 2 O/(N 2 + N 2 O) ratio and DEA. In the laboratory, N 2 fluxes were highest in PFS followed by RNG and CORN. These results indicate that PFS watersheds support greater total denitrification while emitting less N 2 O than croplands. Greater potentially mineralizable C in PFS and RNG suggest C availability is an important factor affecting more complete denitrification. These results suggest PFSs function similar to riparian buffers and have potential to reduce NO 3 − –N losses from annual croplands by denitrification to N 2 .