Effect of soil wetness on air composition and nitrous oxide emission in a loam soil

Authors

• A. JAAKKOLA
• A. SIMOJOKI

DOI: https://doi.org/10.23986/afsci.5612

Abstract

Effects of cropping (bare fallow, grass), heavy irrigation and N fertilization (0, 100 kg ha-1) on soil air (at depths of 15 and 30 cm) and N2O emission were studied in a factorial two-year field experiment in southern Finland. The responses of soil mineral N, dry-matter yield and uptake of N were also determined. Irrigation was performed during two periods in 1993 and one period in 1994. During sampling periods, the soil moisture ranged from 11% to 45% (v/v) and soil temperature from 0°C to 21°C. Unirrigated bare fallow contained 14-21% O2, 0.1-2% CO2 and 0.2-100 µl l-1 N2O (1993 maximum 27 µl l-1) in the soil air. Cropping and irrigation lowered O2 (minimum 3-7%) and raised CO2 (maximum 9%) in soil air, but fertilization had no effect. Irrigation raised N2O in the soil air if nitrate was present abundantly. Consequently, fertilization increased N2O especially in the irrigated bare soil, which still contained plenty of nitrate in autumn 1993. Cropping decreased N2O. The variation in soil air composition was partly explained by that in soil air-space. The average daily N2O-N emission amounted to 0-40 g ha-1 (mean 7 g ha-1) and correlated positively with N2O concentration in the soil air.;