Influence of Liming on Agrochemical Properties of Leached Black Soil and Yield and Quality of Spring Wheat Grain

The paper presents results of studying the effect of leached black soil liming on agrochemical properties of the soil and yield and quality of spring wheat products. The studies were carried out on the experimental field of Ulyanovsk State Agrarian University in 2016–2019. The scheme of the experiment consisted of eight variants: (1) Control (background 1), (2) CaCO₃ 2 t/ha, (3) CaCO₃ 4 t/ha, (4) CaCO₃ 6 t/ha, (5) N40P40K40 (NPK, background 2), (6) NPK+ CaCO₃ 2 t/ha, (7) NPK+ CaCO₃ 4 t/ha, (8) NPK+ CaCO₃ 6 t/ha. The recording area was 32 m² (4 × 8), the plot placement was randomized, and the experiment was repeated four times. For soil liming, chalk from Shilovskiy deposit of Ulyanovsk oblast was used with a CaCO₃ content of 94.17% and MgCO3 of 4.33%. Chalk was applied for basic tillage in autumn and mineral fertilizers (azofoska) in spring for presowing cultivation. Soil samples were analyzed in an accredited laboratory of the Federal State Budgetary Institution SAS Ulyanovskaya, and plant samples were analyzed in the scientific laboratory of Ulyanovsk State Agricultural Academy according to relevant state methods. It was found that liming of leached black soil with chalk from Shilovskiy deposit of Ulyanovsk oblast reduced the exchangeable acidity by 0.35–0.62 pH_KCl units and hydrolytic acidity by 0.21–0.34 meq/100 g of soil. Liming of leached black soil both in pure form and in combination with mineral fertilizer was accompanied by a significant improvement in its nutritional regime: the content of mineral forms in the arable layer increased by 0.42–2.19 mg/kg (8–43%), mobile phosphorus by 27–69 mg/kg, and exchangeable potassium by 9–56 mg/kg of soil. Liming of leached black soil led to an increase of grain yield of spring wheat by 0.24–0.49 t/ha when applied in pure form and by 0.35–0.57 t/ha in comparison with the NPK background with improved product quality. The highest yield was observed when CaO₃ was combined at a dose of 4 t/ha with N40P40K40, which was 4.42 t/ha on average over 3 years (control 2.64 t/ha) with a gluten content of 25.8% (control 21.9 %).