Nitrous oxide production from strongly acid tea field soils

Abstract

Nitrous oxide (N₂O) production from acid (pH 3.60) tea field soil under aerobic conditions was studied in a laboratory experiment. A large amount of N₂O (53 μ N g⁻¹ soil 14 d⁻¹) was produced under aerobic conditions when ammonium and nitrate were added to the soil. It was assumed that the high N₂O production was an inherent property of the soil because soil pre-treatments (e.g., air-drying) did not affect it. A ¹⁵N tracer study indicated that N 2 was not produced from the acid tea field soil. N₂O was produced during biological reactions, and the contribution of N₂O production during chemical reactions to the whole N₂O production was negligible. Nitrapyrin (2-chloro-6-(trichloromethyl)- pyridine) and acetylene (0.1 Pa), which are selective nitrification inhibitors, slightly reduced N₂O production. These results indicate that denitrification is the main process of N₂O production in acid tea field soil. The levels of N₂O production from four tea field soils collected from the same area were compared. The results showed that a large amount of N₂O is likely to be produced from a soil with a pH value below about 3.60 and to which a large amount of nitrogen fertilizer (more than 1,000 kg N ha¹⁻¹ y¹⁻¹) had been added.

Key Words:

• acid tea field soil
• denitrification
• nitrogen fertilizer
• nitrous oxide