Nitrous oxide emissions in southern Poland from agricultural soils under various tillage conditions and from urban soils under strong anthropopression

Abstract:

We present the results of field measurements performed at: (i) the agricultural sites managed by Institute of Plant Acclimatization and Husbandry (ZDHAR) in Grodkowice (Malopolska, Poland), and (ii) the urban sites located in Kraków, Poland.

For agricultural measurements, several sites have been selected for measurements of N₂O emissions during two campaigns – in spring and autumn 2014. The investigated crops were chosen to represent the regional agriculture and included wheat, canola and maize under various tillage conditions, as well as an uncultivated grassland as a control site.

For urban environment, measurement campaigns have been performed at the university’s campus lawn and at a large urban meadow, both located in the centre of Kraków agglomeration. The sites were chosen to be representative of the urban green areas typical of Central Europe.

The static chamber method was chosen to quantify soil-atmosphere N₂O fluxes. Chamber enclosures have been performed every 3-5 days, depending on the conditions prevailing at the sites during the intermediate periods. From each enclosure, five 50-ml air samples have been collected for subsequent analysis of nitrous oxide concentrations. Well-established gas chromatography methods, with a precision of a single N₂O measurement better than 0.5 ppb were employed. The measured concentrations were then used in a linear emission model to calculate N₂O fluxes.

Results of agricultural campaigns show large variability of N₂O emissions, with maximum fluxes in the order of 120 ng N-N₂O m^-2 s^-1, driven mainly by availability of nitrogen in soil and water. For fertilized sites, largest emissions values were observed several days after the rainfall events. Notable differences between sites under alternative tillage techniques have been observed.

Observations at the urban sites revealed significant fluxes of N₂O, with average daily values in some cases exceeding those observed at agricultural fields.