N2O emissions and absorption against a background of CO2 in Eutric Cambisol under different oxidation-reduction conditions
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Instytut Agrofizyki im. Bohdana Dobrzańskiego, Polska Akademia Nauk, ul. Doświadczalna 4, 20-290 Lublin 27, Poland
Publication date: 2020-05-27
Acta Agroph. 2000, (28), 5–132
Nitrous oxide (N2O) emission and absorption and carbon dioxide (CO2) emission from Eutric Cambisol were measured after treatment soils with NO3-N in laboratory incubation experiments. Incubation experiments were designed to investigate the influence of variables such as oxidation-reduction conditions, pH, organic matter content and granulometric composition on denitrification capacity of investigated soils. Results showed that these soils were emitters (cumulative production N2O ranged from 11.4 to 66.5 mg N2O-N kg–1 of soil) as well as reducers (daily sink of N2O ranged from 1.3 to 66.5 mg N2O-N d–1 kg–1 of soil). The range of reduction of N2O under investigation conditions was from 10 to 100% depending on the kind of soil and time of incubation. Production and reduction of N2O were nonlinearly correlated with redox potential (R2 = 0.906 and R2 = 0.966, respectively). The boundary value of redox potential for emission of nitrous oxide was 250 m V and for absorption of N2O was about 200 m V. Redox potential showed a negative correlation with pH value (R2 = 0.685). Eh value decreased with decreasing of NO3-N·in the range from about 10 to 100 mg NO3-N kg–11 of soil. The highest daily reduction of nitrate was observed in the narrow range of Eh value (200-210 mV). The boundary nitrate concentration resulted in distinct drop of redox potential was about 100 mg NO3-N kg–1. Under investigated conditions the maximum emission of N2O was observed at pH range between 4.5-6, but maximum absorption of nitrous oxide occurred at pH about 5.5 to about 7. Differences in the dissimilative reduction of nitrate were observed in the investigated soils. Absorption of N2O occurred simultaneously with the reduction of nitrate and after depletion of NO3– during the course of the experiment. The range of reduced nitrate fluctuated from 22 to 100% depending on the kind of soil and time of incubation. Denitrification rate and sink of nitrous oxide showed high correlation with mineralization of organic matter (R2 = 0.906 and R2 = 0.913, respectively). Daily emission of CO2 ranged from 1.3 to 23.2 mg CO2-C kg–1 d–1 and was correlated with redox potential (R2 = 0.871), organic matter content (R2 = 0.314), and pH (R2 = 0.804). Differences in release of CO2 were 132 noticed in the investigated soils. The lowest cumulative amount of carbon dioxide was found in soils developed from sand (mean 75 mg CO2-C kg–1). Higher emission was observed in soils developed from loam (mean 130 mg CO2C kg–1) and the highest amount of carbon dioxide was obtained in soils developed from silt (mean 210 mg CO2-C kg–1). Relationship between carbon (as CO2) and nitrogen (as N2O) flux reflected by the C/N ratio in the headspace air and relationship between carbon (as CO2 flux) and nitrogen (as NO3 reduced) were calculated. These two ratios describe the character of biochemical processes in the soils particularly their denitrification capacity as well as their ability to sink of nitrous oxide and nitrate reduction.
Emisja i absorpcja N2O na tle emisji CO2 w glebach brunatnych w zróżnicowanych warunkach oksydoredukcyjnych