Research Monitoring Station "Petrodolinskoye" (PTR) of the Regional Centre for Integrated Environmental Monitoring and Ecological Studies (RCIEM) of Odessa National I. I. Mechnikov University (ONU) is located on an actively managed arable land. The site is situated 8 km from the Dniester River, which enters the Black Sea (29 km from the study site). The station is located near the village “Mirnoe” (46º27'22.12''N; 30º20'9.94''E), 27 km southeast of Odessa and was established in 2006 within the framework of the EU FP6 NitroEurope IP (Medinets et al., 2014). The arable field study site is 10 ha in size with a flat topography at an elevation of 66 m above sea level. The soil is a black soil (FAO definition: Chernozems Vermi-Calcic, CH vec), and representative for the south of Ukraine (Medinets et al., 2014b, 2016). The climate is temperate continental, with an annual average air temperature of 10.5 °С (period of 2000-2014), an annual minimum mean of 8.4 °С and an annual maximum mean of 12.5 °С. Total average annual precipitation is 432 mm. The atmospheric total N (TN) deposition rate is moderate at ca. 11.4 kg N ha-1 y-1 with significant organic N contribution of circa 67% (Medinets et al., 2016).
Crop rotation and management.
The study site has been under active agricultural management for more than 200 years, although a detailed history of the agricultural management is unknown. Before autumn 2006 the area was managed by a collective farm (‘kolkhoz’). The study field, 10 ha in size, was leased in autumn 2006 from the Association of Agricultural Enterprises “Granit”. The crop rotation started with wheat in 2006, in the period 2007 – 2014 was onions (2007), tomatoes (2008), barley (2009) and winter wheat (2009/2010) followed by winter onion (2010/2011), carrot (2011), tomato (2012), red beetroot (2013) and onion (2014) followed by winter wheat. This rotation is typical for this region. Crops (except cereals) were grown with drip irrigation (installed in 5-10 cm depth), with fertilizer applied together with the irrigation (fertigation). E.g., during the study period of 2012-2014 the field was fertilized with mineral NPK fertilizers (see Medinets et al., 2016). To prevent plant diseases and to suppress weeds, pesticides and herbicides were applied to all crops following farmers practice. The following tillage methods were used: deep ploughing (40 cm depths), disking (10 cm depth), harrowing (10 cm depth), cultivation (10 cm depth), inter-row cultivation (5 cm depth); the soil was also disturbed under installation/ removing of irrigation tubes (see Medinets et al., 2016).
