Emission of Nitrous Oxide and Denitrification from Danish Soils Amended with Slurry and Fertilizer

Abstract

Interactions between crops and soil factors in relation to N20 emission and denitrification from soil are not well understood. This study was conducted to determine N-emission from arable soil under various crops in Denmark as a part of a larger European investigation. Denitrification losses from a coarse sandy loam cropped with spring barley, fodder beets or spring rape, and from a fine sandy loam under spring barley or winter wheat were measured during a 2-years period. In the measuring years 1992 and 1993, the N 2 0-emission factors varied from 0.2 to 5 kg N ha-I yr-I between the four different crops and the two soil types. Due to the high spatial variability, the 95% confidence interval for the mean varied between 0.7-40 kg N ha-I yr-I for the highest emission and between 0.05-0.7 kg N ha-I yr-I for the lowest emission. The highest emission occurred from the fine sandy loam soil cropped with spring barley and fertilized with cattle slurry supplemented with inorganic fertilizer. The lowest emission occurred during a dry year (1993) on the coarse sandy soil cropped with spring barley and fertilized with inorganic nitrogen. A similar low emission was measured from a soil cropped with winter wheat despite of a larger amount of nitrogen applied. From this study it became evident that N20-emission during periods with low soil moisture was produced by nitrification and that the emission was dependent on agricultural management and weather, and that no single emission factor can be used for a given soil type.