Changes in the key agrochemical properties of soddy-podzolic soil after fertilisation of jerusalem artichoke with sewage sludge

Studies have shown that the introduction of sewage sludge and composts based on it under Jerusalem artichoke significantly affects the change in agrochemical parameters of soddy-medium-podzolic soil, contributing to an increase in the content of alkaline-hydrolysed nitrogen compounds by 2.2-13.4 mg/kg of soil compared to the control and determining the content at the level of 51.2-56.5 mg/kg of soil in the upper (0-20 cm) and 27.9-31.6 mg/kg of soil – in the lower (20-40 cm) soil layer. The content of ammonium nitrogen compounds in the variants with fertiliser application fluctuated in a small range of values (16-21 mg/kg of soil) and increased under the influence of increasing fertilizer doses. Along with the change in the content of nitrate nitrogen, this contributed to an increase in the content of mineral nitrogen compounds in the soil in the range of 18.5-23.4 mg/kg of soil in the arable (0-20 cm) and 19.8-21.9 mg/kg of soil – in the subsoil (20-40 cm) layers, which is 1.7-2.2 mg/kg of soil higher than the control variant. The highest values of mineral nitrogen compounds were recorded in the variant where the highest dose of sewage sludge – 40 t/ha and mineral fertilisers were applied (N10P14K58). Despite a wide range of nitrogen content values for alkaline hydrolysed compounds and mineral nitrogenous compounds, their ratio remained stable and amounted to 2.3-2.6 in the upper and 1.3-1.5 in the lower (20-40 cm) soil layer, and also decreased with increasing fertiliser application dose. That is, this parameter varied insignificantly depending on the dose of fertiliser application. The content of mobile phosphorus compounds in the variants with the use of fertilisers fluctuated in the range of values (77.5-98.5 mg/kg of soil) and increased under the influence of sewage sludge and composts based on it, which exceeded the control values by 14.6-35.6 mg/kg of soil. The highest rates of mobile phosphorus compounds were recorded in the variant where sewage sludge was applied – 40 t/ha and N10P14K58.10P14K58. The introduction of sewage sludge at a dose of 20-40 t/ha contributed to an increase in the content of exchangeable potassium compounds at the level of 89.3-97.2 mg/kg of soil in the upper (0-20 cm) and 83.1-93.4 mg/kg of soil – in the lower (20-40 cm) layer, which is more than 42.1 mg/kg of soil exceeded the control variant. To a lesser extent, the content of exchangeable potassium compounds increased with the introduction of composts based on sewage sludge and straw. The correlation and regression analysis indicates that the coefficient of phosphorus concentration in the soil depends to the greatest extent on the content of its mobile compounds with the coefficient of determination R2 = 0.70. The potassium concentration coefficient closely (R2 = 0.91) correlates with the content of its metabolic compounds in the soil