Spatial and temporal variability of nitrous oxide emissions in a mixed farming landscape of Denmark

[摘要] Nitrous oxide (N₂O) emissions from agricultural land are variable atthe landscape scale due to variability in land use, management, soil type,and topography. A field experiment was carried out in a typical mixedfarming landscape in Denmark, to investigate the main drivers of variationsin N₂O emissions, measured using static chambers. Measurements weremade over a period of 20 months, and sampling was intensified during twoweeks in spring 2009 when chambers were installed at ten locations or fieldsto cover different crops and topography and slurry was applied to three ofthe fields. N₂O emissions during spring 2009 were relatively low, withmaximum values below 20 ng N m⁻² s⁻¹. This applied to all land usetypes including winter grain crops, grasslands, meadows, and wetlands. Slurryapplication to wheat fields resulted in short-lived two-fold increases inemissions. The moderate N₂O fluxes and their moderate response toslurry application were attributed to dry soil conditions due to the absenceof rain during the four previous weeks. Cumulative annual emissions from twoarable fields that were both fertilized with mineral fertilizer and manurewere large (17 kg N₂O-N ha⁻¹ yr⁻¹ and 5.5 kg N₂O-N ha⁻¹ yr⁻¹)during the previous year when soil water conditions werefavourable for N₂O production during the first month followingfertilizer application. Our findings confirm the importance of weatherconditions as well as nitrogen management on N₂O fluxes.

[学科分类] 地球化学与岩石