Effect of Inorganic N Composition of Fertilizers on Nitrous Oxide Emission Associated with Nitrification and Denitrification

Abstract

We studied the effect of repeated application (once every 2 d) of a fertilizer solution with different ratios of NH₄ ⁺ - and NO₃ ⁻-N on N₂O emission from soil. After the excess fertilizer solution was drained from soil, the water content of soil was adjusted to 50% of the maximum water-holding capacity by suction at 6 × 10³ Pa. Repeated application of NH₄ ⁺- rich fertilizer solution stimulated nitrification in soil more than NO₃ ⁻-rich fertilizer. Although the evolution of N₂O through nitrifier denitrification tended to increase with the repeated addition of a fertilizer solution rich in NH₄ ⁺ rather than in NO₃ ⁻, the contribution of nitrifier denitrification remained at levels of 20 to 36% of the total emission regardless of the inorganic N composition. The total emission of N₂O also tended to increase with the application of NH₄ ⁺- rather than NO₃ ⁻-rich fertilizer. It was suggested that the coupled process of nitrification and denitrification at micro-aerobic sites became important when fertilizer rich in NH₄ ⁺ was applied to soil under relatively aerobic conditions.

Keywords:

• denitrification
• inorganic N
• nitrification
• nitrifier denitrification
• nitrous oxide

Notes

presentaddress: 1Kyushu Kankyo Shido Center Co., Ltd., 5–8–17, Hakata-Eki Minami, Hakata-ku, Fukuoka, 812–0016 Japan.