Dynamics of nitrogen content under the influence of different methods of root fertilization of winter wheat in the conditions of the Northern Steppe of Ukraine

Abstract

Purpose. To establish patterns of available nitrogen forms (nitrate and ammonium) dynamics in ordinary heavy-loamy chernozem of the Northern Steppe of Ukraine depending on different methods and timing of root feeding of winter wheat with urea-ammonium nitrate (UAN) and solid nitrogen fertilizers, particularly to evaluate the efficiency of CULTAN technology (deep injection localized UAN application) compared to traditional surface methods, to determine the nitrogen utilization coefficient, nitrogen balance and the impact of technologies on soil microbial activity. Methods. Field experiments were conducted in 2023–2025 on the fields of “Preobrazhenivske” LLC (Pavlohrad district, Dnipropetrovsk region) on ordinary heavy-loamy chernozem. A one-factor field experiment with 8 fertilization variants at equal nitrogen rate N60 was established: control (no fertilizer); CULTAN UAN in autumn N30 + spring N30; UAN spraying in spring N60; combined schemes; single CULTAN UAN in spring N60; traditional broadcasting of ammonium nitrate and ammonium sulphate by Buznytskyi method. Nitrate and ammonium nitrogen content was determined in 0–10, 10–20, 20–30 cm layers at key growth stages using spectrophotometric method and after seven-day composting. Nitrogen balance was calculated from the difference between crop removal and applied amount. Soil microbial activity was assessed by respiration intensity, cellulolytic activity and the number of ammonifying and nitrifying bacteria. Results. CULTAN UAN technology provided prolonged nitrogen availability during the vegetation period: the maximum nitrate nitrogen content (20.6–24.1 mg/kg) was observed at the stem elongation–heading stages, and the residual content before harvesting was 1.7–2.1 times higher than with traditional surface methods. Single spring CULTAN UAN application (N60) provided the highest nitrogen utilization coefficient – 73.3 % (2.4–4.4 times higher than surface spraying and solid fertilizer broadcasting), nitrogen removal with the harvest – 122 kg/ha and the lowest balance deficit (–62 kg/ha). Traditional methods were characterized by high non-productive losses (70–83 %) due to ammonia volatilization and surface crust formation. CULTAN UAN application stimulated soil microbial activity: soil respiration increased by 20 %, cellulolytic activity – by 20 %, beneficial microflora abundance – by 34–52 % compared to control, while traditional methods suppressed it by 32–48 %. Conclusions. Under the arid conditions of the Northern Steppe of Ukraine, the most effective method of winter wheat root feeding is single spring deep injection UAN application using CULTAN technology at the rate of N60. This method increases the nitrogen utilization coefficient to 73.3 %, reduces non-productive losses by 4–5 times, ensures prolonged nutrient availability during the period of maximum plant demand, preserves and activates soil microbial activity, thereby contributing to maintaining soil fertility and ecological safety of fertilization technology.