Denitrification in an acid soil: effects of slurry and potassium nitrate on the evolution of nitrous oxide and on nitrate-reducing bacteria |
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| Authors: | Søren Christensen |
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| Institution: | State Laboratory for Soil and Crop Research, 24, Lottenborgvej, 2800 Lyngby, Denmark |
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| Abstract: | The N2O-flux from an acid soil in the field (limed to pH 5.4) was calculated from measurements of N2O in the gas flow through a soil cover. The N2O-flux showed a seasonal variation and was also influenced by the presence of growing plants. The addition of liquid manure (slurry) resulted in N2O-fluxes of up to 23g N ha?1 day?1 during the spring, in contrast to a maximum of 5 g N ha?1 day?1 from soil supplied with KNO3 or from unfertilized soil. The mean N2O-turnover rate in the 0–30 cm soil layer was 5 times per day. Laboratory incubations in the presence and absence of acetylene suggest that no N2 was formed in association with N2O. The number of N-gas producing bacteria was increased by addition of slurry but not by addition of KNO3. The denitrifying activity increased in the same order. Three groups of nitrate-reducing bacteria producing N-gas were isolated: dominantly N2-formers, for example P. fluorescens, dominantly N2O-formers, mainly Pseudomonas spp, and dominantly NO2?-formers, mainly Bacillus spp. |
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