Nitrous oxide emissions from the soil under different fertilization systems on a long-term experiment

The research aimed at the assessment of N2O emission from agricultural soils subject to different fertilization conditions. It was carried out on a long-term experiment field in Skierniewice in Central Poland maintained with no alterations since 1923 under rye monoculture. The treatments included mineral (CaNPK), mineral-organic (CaNPK + M) and organic (Ca + M) fertilization. Measurements were conducted during the growing periods of 2012 and 2013. N2O emissions from the soil were measured in situ by the means of infrared spectroscopy using a portable FTIR spectrometer Alpha. N2O fluxes over the measurement periods showed high variability with range 0.13-11.20 g N2O-N/ha/day (median 2.87, mean 3.16) from mineral treated soil, 0.23-11.06 g N2O-N/ha/day (median 3.64, mean 3.33) from mineral-organic treated soil and 0.25-12.28 g N2O-N/ha/day (median 3.14, mean 3.55) from organic treated soil. N2O fluxes from manure-treated soils were slightly higher than those from soils treated exclusively with mineral fertilizers. N2O fluxes were positively correlated with soil temperature, air temperature, and content of both, NO3- and NH4+, in the soil (0-25 cm) and, to a lesser degree, negatively correlated with soil moisture. Based on the measured N2O flux and its relationship with environmental factors it can be concluded that both, nitrification and denitrification the are important sources of N2O in mineral soils of Central Poland, where the average soil water-filled pore space during the growing period range from 22-35%. Under the climate, soil and fertilization conditions in Central Poland, the N2O emission from cultivated soils during the growing period is approximately estimated as 0.64-0.73 kg N/ha.