Fertigation effect on seasonal variations in excangable soilacidity of grasslandchernozem soils in apple orchards

According to various literature sources, optimal levels of exchangeable soil acidity (pH KCl ) for growing apple trees range within pH 5.5–7.5. In 2020–2021, we conducted experiments under the conditions of the Tambov Oblast in an experimental apple orchard of the I. V. Michurin Federal Research Centre to examine the dynamics of soil acidity variations in apple orchards under the infl uence of fertigation with water-soluble mineral fertilizers and drip irrigation. Soil sampling was conducted in two plots: (1) with drip irrigation and fertigation and (2) with drip irrigation without fertilization. During the growing season, 9–11 soil samples were collected from a depth of 0–20, 20–40, and 40–60 cm to determine soil acidity. The pH level of soil salt extracts was determined by an Expert-001 pH meter (Russia). During fertigation with mineral fertilizers, a signifi cant increase in soil acidity was observed in all the studied layers. The 0–20 cm layer showed the most pronounced variations in рН KCl values. During the May–July period of 2020, i.e., when applying the main share of the annual fertilizer amount, a sharp increase in soil acidity (from pH 5.46 to 4.88) followed by its partial recovery (down to pH 5.13) was observed. In 2021, a similar soil acidity trend was noted, when рН KCl grew from 5.56 to 4.92, although without a signifi cant partial recovery by the end of the season. In deeper soil layers, the fl uctuations in рН KCl values were not that noticeable. Thus, the most pronounced decrease in рН KCl was observed in the period of nitrogen application. Therefore, the results obtained confi rm a distinct relationship between fertigation irrigation and changes in exchangeable soil acidity. The average values of рН KCl in both 2020 and 2021 showed that, following fertilizer application, soil acidity increased with an increase in sampling depth, during both drip and sprinkle irrigation. The data obtained can be useful when developing soil fertigation programs in intensive apple orchards