The Nitrogen Regime of Haplic Luvisol under a Cherry Orchard and the Yield of Trees Associated with the Application of Fertilizers

The dynamics of mineral nitrogen compounds (N–NH₄ and N–NO₃) in the root zone of a sour cherry orchard in 2018–2022 has been investigated to estimate the nitrogen doses essential for this fruit crop in first decade after planting. The field experiment has been carried out at the orchard located in the forest-steppe zone of the Central Russian upland (Orel oblast). Urea and potassium sulfate have been applied to soil annually at early spring with doses increasing from N30K40 to N120K160. The dynamics of N–NH₄ in the soil of fertilized and unfertilized experimental plots is similar; the lowest levels of the indicator are typical for July during the fruit ripening period. The N–NO₃ content in unfertilized soil varies slightly through the vegetation period. Fertilizer application leads to more intensive seasonal fluctuations of N–NO₃ that depend on the weather conditions. Annual fertilization led to annual increase of N–NH₄ and N–NO₃ content by 2–12 and 18–70 times, respectively, depending on the dose of nitrogen in the fertilizer. However, mineral nitrogen does not accumulate in the root zone over the years. Soil treatment with fertilizers has no effect on the sour cherry yield if the application rates are less than 15 t/ha. In the high-yield period, fertilizer application in a dose of N60K80 was necessary to reach a yield of 20 t/ha.