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A three-year field experiment was conducted under conditions of Luvic Chernozem soil. Diversified nitrogen fertilization with 0, 60, 120, and 180 kg N ha^-1, and microbial preparations improving soil properties were applied to potatoes, cv. ‘Satina’, cultivation. N–NO₃ concentration in the soil profile (0–0.9 m) in autumn after potato harvesting fluctuated from 28 kg N ha^{-1 in the N}₀ treatment to 70 kg N ha^{-1 in the N}₁₈₀ treatment, whereas N–NH₄ content varied from 22 to 48 kg N ha^-1, respectively. The level of nitrogen fertilization also had a significant effect on the change in soil N–NO₃ content during the autumn-winter period. The decrease in N–NO₃ content in the N₀ treatments was 7% compared to 24% in the N₁₈₀ treatments. Application of microbial preparations to potato cultivation caused an increase in N_min content in soil after crop harvesting. However, after the autumn-winter period, a lower amount of N–NO₃, compared to the control treatment, was found in the treatments where microbial preparations had been used. 

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Fertilization of plants in greenhouse soilless cultivation is used in a closed system with recirculating nutrient solution or in an open system where the excess of nutrient solution is discharged into the soil or sewage. In Poland, most of basic greenhouse vegetables are grown in the open soilless system. The excess of highly concentrated nutrient solution leaking from growing slabs causes contamination of soil and shallow groundwater. The aim of the study was to monitor component changes in nutrient solution and nitrate nitrogen in the plant root zone, drainage water, as well as in shallow groundwater present in arable lands in the immediate vicinity of the soilless tomato culture. The study was conducted in 2013 - 2015 and compared tomato cultivated in Rockwool versus biodegradable organic substrate. Changes of nutrient content including N-NO₃ in the root zone and drainage water depended on the type of the substrate in which tomato plant was cultivated as well as on the plant growth stage. Higher content of nitrate nitrogen in the root zone and drainage water was found in tomatoes grown in Rockwool compared to the organic substrate. The peak content of N–NO₃ (117 mgdm^-3)was detected in the groundwater present directly under the soilless tomato culture and it decreased proportionally to the distance from the greenhouse.