Can N Fertilizer Addition Affect N 2 O Isotopocule Signatures for Soil N 2 O Source Partitioning?

Peiyi Zhang, Teng Wen, Yangmei Hu, Jinbo Zhang and Zucong Cai
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Peiyi Zhang: School of Geography Science, Nanjing Normal University, Nanjing 210023, China
Teng Wen: School of Geography Science, Nanjing Normal University, Nanjing 210023, China
Yangmei Hu: School of Geography Science, Nanjing Normal University, Nanjing 210023, China
Jinbo Zhang: School of Geography Science, Nanjing Normal University, Nanjing 210023, China
Zucong Cai: School of Geography Science, Nanjing Normal University, Nanjing 210023, China

IJERPH, 2021, vol. 18, issue 9, 1-10

Abstract: Isotopocule signatures of N 2 O (? 15 N bulk , ? 18 O and site preference) are useful for discerning soil N 2 O source, but sometimes, N fertilizer is needed to ensure that there is enough N 2 O flux for accurate isotopocule measurements. However, whether fertilizer affects these measurements is unknown. This study evaluated a gradient of NH 4 NO 3 addition on N 2 O productions and isotopocule values in two acidic subtropical soils. The results showed that N 2 O production rates obviously amplified with increasing NH 4 NO 3 ( p < 0.01), although a lower N 2 O production rate and an increasing extent appeared in forest soil. The ? 15 N bulk of N 2 O produced in forest soil was progressively enriched when more NH 4 NO 3 was added, while becoming more depleted of agricultural soil. Moreover, the N 2 O site preference (SP) values collectively elevated with increasing NH 4 NO 3 in both soils, indicating that N 2 O contributions changed. The increased N 2 O production in agricultural soil was predominantly due to the added NH 4 NO 3 via autotrophic nitrification and fungal denitrification (beyond 50%), which significantly increased with added NH 4 NO 3 , whereas soil organic nitrogen contributed most to N 2 O production in forest soil, probably via heterotrophic nitrification. Lacking the characteristic SP of heterotrophic nitrification, its N 2 O contribution change cannot be accurately identified yet. Overall, N fertilizer should be applied strictly according to the field application rate or N deposition amount when using isotopocule signatures to estimate soil N 2 O processes.

Keywords: isotopocule; nitrous oxide; N fertilizer; soil incubation (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2021
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