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How does management legacy, nitrogen addition, and nitrification inhibition affect soil organic matter priming and nitrous oxide production?
Author(s) -
Thilakarathna Shakila K.,
HernandezRamirez Guillermo
Publication year - 2020
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.1002/jeq2.20168
Subject(s) - hordeum vulgare , festuca arundinacea , agronomy , chemistry , nitrification , urea , bromus inermis , soil water , organic matter , lolium perenne , zoology , nitrogen , perennial plant , biology , forage , poaceae , ecology , organic chemistry
Long‐term management of croplands influences the fluxes and sources of nitrous oxide (N 2 O). We examined this premise in a greenhouse study by using soils collected from a 38‐yr‐old field experiment. The sampled treatments were continuous barley ( Hordeum vulgare L.; CB), continuous fescue ( Festuca rubra L., F. arundinacea Schreb; CF), and two phases of an 8‐yr rotation: faba bean ( Vicia faba L.; FB) and alfalfa ( Medicago sativa L.)–bromegrass ( Bromus inermis Leyss) hay. Barley was grown as a test crop in the greenhouse in each soil. The ranking of N 2 O emissions was hay > FB > CB > CF ( P < .001). We quantified the 15 N‐site preference to assess the N 2 O‐producing processes. Denitrification was the predominant source, contributing 77.4% of the N 2 O production. We also evaluated nitrogen (N) additions: urea alone or urea with a nitrification inhibitor (nitrapyrin or DMPSA). Compared with urea alone, nitrapyrin and DMPSA reduced N 2 O emissions by 16 and 25%, respectively. We used urea labeled with 15 N to trace N to N 2 O emissions, aboveground plant N uptake, and N retention by soils. Total 15 N‐recovery (N 2 O + plant + soil) was highest under FB (86%) and lowest under CB (29%). We further separated the N 2 O derived from urea versus N 2 O from soil organic matter (SOM). The inhibitor DMPSA reduced the N 2 O derived specifically from added urea‐N by more than half ( P < .001). With the addition of urea, N 2 O production from mineralization of SOM‐N accelerated over the control (without urea), termed the priming effect. This priming of SOM‐N contributed with 13% of the total N 2 O production when averaged across the four management legacies. The CB soil had the highest proportion of priming‐derived N 2 O (24%). Management legacies clearly differed in soil carbon and N, which governed N 2 O production from denitrification and SOM priming.