Assessment of various practices of the mitigation of N2O emissions from the arable soils of Poland
Authors: Sosulski Tomasz , Szymańska Magdalena , Szara Ewa 
Published: June 2017

This review assesses the adaptability and effectiveness of the basic practices to mitigate the N2O emissions from the arable land in the climate, soil and agricultural conditions of Poland. We have analyzed the decrease in the nitrogen-based fertilization, selection of the fertilizer nitrogen forms, use of biological inhibitors of nitrogen transformation in the soil, control of the acidic soil reaction, reduction in the natural fertilizers use and afforestation of the low productive soils. The challenge evaluating the effectiveness of mitigation practices lies in the inadequacy of the national data on N2O soil emissions in particular agrotechnical conditions. In Poland, circumstances that favor intensive N2O emissions from the arable soils occur uncommonly, as shows the analysis of the literature reporting on the country climate, soil and agricultural conditions alongside the N2O emissions from soils under various cultivation conditions. Consequently, the effectiveness of mitigation practices that relies on an extensification of plant production may be insufficient. It can be assumed that, at the doses of nitrogen fitting the nutritional needs of crops, the soil N2O emissions are low and do not meaningfully differ from the emissions from untreated soils (literature data point to limited N2O emission from arable soils treated with N doses of ≤150-200 kg N·ha-1). The effectiveness of the nitrogen fertilization reduction as an N2O emissions mitigation practice is restricted to intensive farming. A universal registry of the mineral and natural fertilization use could help identify the agricultural holdings with a potential for high N2O emission and foster a targeted application of mitigation practices. It is suggested that normalization and maintenance of the optimum (i.e. close to neutral) soil pH should become a more common practice of N2O emissions mitigation in Poland in view of the extent of arable soils acidification and the literature data that indicate elevated N2O emissions from acid soils. Application of urease and nitrification inhibitors alongside nitrogen fertilization can be considered an effective practice of N2O emissions mitigation. Owing to economic reasons the use of nitrogen fertilizers with such additives is currently limited to non-agricultural segments of plant production. Afforestation of the low productive soils offers an attractive opportunity for mitigation of N2O emissions. Whereas N2O emissions from forest soils are considerably lower compared with those from the arable ones, the literature indicates that no N2O emissions mitigation is attained through a conversion of arable land to agroforestry. Considering the current forest area of Poland (24.9% of the total area) and the plans to increase the afforestation rate (to 33% in 2050) the measurable effects of this mitigation practice will only be seen in a long-term perspective.

Besides identifying and excelling the mitigation practices the authors postulate a review of the algorithms employed by the National Centre for Emissions Management (KOBiZE) for the calculation of the GHG emissions. Solutions applied by KOBiZE appear to address mainly the area - or population-related aspects and, to a much lesser degree, the actual N2O production. In this context, the effects of certain N2O emissions mitigation practices might be difficult to be taken into consideration. The application of national statistics of the use of mineral and natural fertilizers to the calculation of the N2O emissions from the arable soils might be questioned given that the N2O emissions are driven by the actual local N dose.