Fertiliser Induced Nitrous Oxide Emissions During Energy Crop Cultivation On Loamy Sand Soils

摘要

Nitrous oxide (N_2O) fluxes from a loamy sand soil have been collected at an experimental field since 1999. To study the nitrogen (N) fertiliser induced emissions, annual crops and perennial plants received three different levels of N fertilisation: 0, 75, and 150 kg N ha~(-1). N_2O was measured by gas chromatography and closed chamber technique. Water content of the soil was determined gravimetrically and the soil content of mineral N by ion chromatography. The N_2O fluxes were below 30 μg N_2O m~2 h~(-1) during the winter season and varied from 10 to more than 1000 μgN_2O m~(-2) h~(-1) in the course of the vegetation season. N_2O emissions after N fertilisation were assigned to fertiliser induced emissions. High N_2O emissions at the end of the vegetation period are the result of increased mineralisation of soil organic matter. N_2O emissions from freeze-thaw cycles gave only a small contribution to the total annual N_2O emission budget from all blocks studied. Since the mean soil moisture content is very low (10%) and the water-filled pore space (WFPS) correlates negatively with N_2O emissions, nitrification is considered the main source for N_2O emissions. Evaluation of the data regarding dependence on fertilisation level indicates that N_2O fluxes are positively correlated to soil NO_3-N content. The N_2O fluxes from annual crop plots are higher than those from plots with perennial plants (grass, willow, poplar). The mean N_2O-N emission factor for fertiliser induced emissions from tilled soil is 1.0% in contrast to that of non-tilled soil with 0.7%. The mean fertiliser induced N_2O-N emissions, averaged over all crops and the total period of nine years, are in the range of 0.8 ± 0.2% of the N fertiliser applied.