Knowledge of the mineralisation and nutrient release of organic fertilisers is essential to ensure plant nutrient demand and availability, to increase N use efficiency and to minimise environmental risks. In 2018–2020, two similar field experiments were carried out on clay loam Cambisol with winter wheat (Triticum aestivum L.) grown without N application and applying liquid anaerobic digestate (LD), pig slurry (PS) and ammonium nitrate (AN) fertilizer with and without additional fertilization (N₁₂₀ and N₁₂₀₊₅₀). The aim of the research was to compare the effect of organic and mineral fertilizers on the variation of soil mineral nitrogen forms in the 0–30, 30–60 cm soil layers and N accumulation in wheat yield. Fertilizers applied during the previous growing season increased the nitrate and ammonium nitrogen (N-NO₃ and N-NH₄) content after the resumption of winter wheat vegetation. The dry period in spring (2019) had a negative impact on winter wheat N uptake. In a year of normal moisture content (2020), PS and LD fertilizers and the fertilizer application of the previous year (2019) significantly increased the N-NO₃ content in the topsoil, while all applied fertilizers increased it in the deeper soil layer (by a factor of between 3.6 and 12.3), compared to unfertilized soil.

Biogas slurry is widely used to fertilize crops. However, their impact on soil parameters and waxy winter wheat (Triticum aestivum L.) nutrition is poorly understood. The aim of this research was to determine the influence of liquid anaerobic digestate and pig slurry applied to waxy winter wheat on the dynamics of soil organic carbon (SOC) and total nitrogen (N_tot) in different forms on grain yield, and to compare them with the use of ammonium nitrate. The nitrogen rates (kg N·ha⁻¹) used for fertilization were N0, N60, N120, and N120+50. The study showed that the variation of nitrate nitrogen (N-NO₃) and water-extractable organic carbon (WEOC) in the soil during the growing season depended on N fertilizer rates, meteorological conditions of the year, and, to a lesser extent, on fertilizer forms. Meteorological conditions were responsible for the demand and supply of nutrients from the soil by the waxy winter wheat variety. This determined the wheat yield and the variation in the soil parameters studied. Over the 2 years, the soil C:N ratio decreased, especially at the medium and high N fertilizer rates. The lowest changes were observed in the unfertilized and fertilized plots at a rate of 60 kg N·ha⁻¹.