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B51 Study on anthropogenic sources and sinks of greenhouse gases
(2) Study on sources and sinks of atmospheric CH₄ and N₂O
­¤Development of mitigation options of nitrogen oxides emission from agro-ecosystems in Asia

EF Fellow

Aixin Hou (Institute of Applied Ecology)
Laboratory of Ecological Process of Trace Substances in
Terrestrial Ecosystem, Chinese Academy of Sciences
Wenhua Road, Shenyang 110015, China
Tel: 86-24-23916240

[Contact Person]

Haruo Tsuruta
Head
Laboratory of Environmental Impact Assessment
Department of Environmental Planning
National Institute of Agro-Environmental Sciences
Kannondai 3-1-1, Tsukuba, Ibaraki 305, Japan
Tel: 81-298-38-8276 Fax: 81-298-38-8199
Email: Tsuruta@niaes.affrc.go.jp

Total Budget for FY 1998:

2,000,000 Yen

Abstract

Nitrous oxide (N₂O) and nitric oxide (NO) emissions from soil are affected by many factors. Nitrogen source supply to the soil, especially N fertilizer input, soil moisture and soil type appear to be the most important factors to control the N₂O and NO emission rate. In this study, incubation experiments were conducted to determine the effect of the urea form and the soil moisture on N₂O and NO emissions in Japanese Andosols. The results showed that there were no significant differences in the total amount of N₂O and NO emissions over 77 days between non-coated urea treatment and coated urea treatment except for NO emission at 40% wfps (water filled pore space) where it was reduced by 23% when coated urea was applied. But as compared to easily decomposable urea, coated urea did reduce N₂O and NO emissions in the earlier period shortly after fertilization. The results also indicated that soil moisture had a much more significant effect on N₂O and NO emissions than the form of urea, especially for N₂O. From 40% to 100% wfps, there were a positive relationship between N₂O emission and soil water content and a negative relationship for NO. The flux ratio of NO/N₂O was governed by soil moisture with a greatest value at the lowest wfps treatments for each fertilizer treatment. The soil moisture condition could be the most important controlling factor for N₂O and NO emissions when a rich N supply existed in soil.

[Key Words]

Nitrous oxide flux, nitric oxide flux, soil moisture (wfps), coated urea