The change of the main agrochemical indicators of the sod-podzolic soil for the submission of the municipal wasterwater under the artichoke

The studies have shown that the introduction of sewage sludge and compost made on its basis, significantly affects the change in the agrochemical parameters of the sod-medium-podzolic soil, increasing the content of the alkaline hydrolysed nitrogen compounds by 2.2 – 13.4 mg/kg of the soil compared to with control and determining the size of its values at the level of 51.2 – 56.5 mg/kg of the soil in the upper (0 – 20 cm) and 27.9 – 31.6 mg/kg – in the lower (20 – 40 cm) soil layer. The content of the ammonium nitrogen compounds in the variants with the fertilizer application fluctuated in a small range of the values (16 – 21 mg/kg of soil) and increases under the influence of increasing fertilizer doses. Together with the change in the content of the nitrate nitrogen, this contributed to an increase in the content of the mineral nitrogen compounds in the soil in the range of 18.5 – 23.4 mg/kg of the soil in arable (0 – 20 cm) and 19.8 – 21.9 mg/kg of the soil – in subsoil (20 – 40 cm) layers, which by 1.7 – 2.2 mg/kg of the soil exceeded the control variant. The highest indicators of the mineral nitrogen compounds were recorded in the variant where the highest dose of the sewage sludge was applied – 40 t/ha and mineral fertilizers (N10P14K58). Despite the wide range of the nitrogen content values of the alkaline hydrolysed compounds and mineral nitrogen compounds, their ratio remained stable and was 2.3 – 2.6 in the upper and 1.3 – 1.5 in the lower (20 – 40 cm) soil layer, and also decreased with the increasing dose of the fertilizer. That is, this indicator did not change significantly depending on the fertilizer application rate. The content of the mobile phosphorus compounds in the variants with the use of the fertilizers fluctuated in the range of the values (77.5 – 98.5 mg/kg of the soil) and increased under the influence of the introduction of the sewage sludge and compost based on it, which is 14.6 – 35.6 mg/kg of the soil was dominated by the control indicators. The highest rates of the mobile phosphorus compounds were recorded in the variant where the sewage sludge were applied – 40 t/ha and N10P14K58. The introduction of the sewage sludge at a rate of 20 – 40 t/ha contributed to an increase in the content of the potassium metabolites at the level of 89.3 – 97.2 mg/kg of the soil in the upper (0 – 20 cm) and 83.1 – 93.4 mg/kg – in the lower (20 – 40 cm) layer, which exceeded the indicators of the control variant by more than 42.1 mg/kg of the soil. The content of the potassium metabolic compounds increased somewhat less with the introduction of the composts based on the sewage sludge and straw. The results of the correlation-regression analysis indicate that the phosphorus concentration coefficient in the soil largely depends on the content of its mobile compounds and is marked by the coefficient of the determination R2 = 0.70. The potassium concentration coefficient is closely (R2 = 0.91) correlated with the content of its metabolic compounds in the soil.