Nitrous oxide flux from a tea field amended with a large amount of nitrogen fertilizer and soil environmental factors controlling the flux

Abstract Nitrous oxide (N2O) is one of the main greenhouse gases, and accurate estimation of the N2O flux from fertilized arable land is required. It is known that acidic tea field soil displays a higher N2O production activity than neutral arable soil and that tea fields could be a major source of N2O. Therefore, N2O fluxes from four plots (Std, 2N, 2Ca and −Ca plots) in a tea field that had been subjected to different conditions of fertilizer management were measured using the closed chamber method over a period of two years, and the relationships between the N2O flux and soil environmental factors were analyzed. The amounts of nitrogen fertilizer and liming material (dolomite) applied to the Std plot were 600 kg N ha−1 y−1 and 1,500 kg ha−1 y−1, respectively. The amount of nitrogen fertilizer applied to the 2N plot was two-times larger than that applied to the Std plot and corresponded to the conventionallevel in Japanese tea fields. The soil was acidified due to heavy nitrogen fertilization in the 2N plot. The 2Ca plot was amended with two-times the amount of liming material of the Std plot and in the −Ca plot no liming material was applied. There were significant differences among the N2O fluxes from the plots, and the highest value of N2O flux was 8.785 mg N m−2 h−1 in the 2N plot. Annual emission rate and emission factor of N2O in the 2N plot were 25.22 kg N2O-N ha−1 and 2.10%, respectively. Both long-term heavy nitrogen fertilization and subsequent soil acidification possibly enhanced the N2O flux from the tea field. The N2O flux from the tea field showed temporal variations, namely the N2O flux was relatively low from December to March possibly due to the low soil temperature and it increased gradually after March as the soil temperature increased over 10°C. The N2O flux reached the first major peak in July, decreased transiently in August presumably due to the drying of soil, increased again and reached the second peak in September or October, and then decreased after November. Multiple linear regression analysis of the relationships between the N2O flux and soil environmental factors indicated that the N2O production activity was significantly related to the N2O flux from the tea field. The N2O production activity showed temporal variations corresponding to the temporal variations of the N2O flux.