ASSESSMENT OF SOIL FERTILITY IN THE USTIA RIVER BASIN ACCORDING TO THE COMPLEX AGROCHEMICAL SCORE

Abstract

The article analyzes the main fertility indicators of light gray, dark gray, podzolized forest soils and podzolized chernozem soils of the Ustia River basin for the period 2011–2022. The soil cover of the basin is predominantly formed on loess-like loams and loess. Light gray podzolized forest soils of the Zdolbuniv district (Orestiv village) are characterized by a humus content of 2.4%, an average content of easily hydrolyzable nitrogen of 115 mg/kg, a high content of available phosphorus of 180 mg/kg, a low content of exchangeable potassium of 65 mg/kg, and a pH value of 5.8. Dark gray podzolized forest soils of the Rivne district (Zaborol, Rysvyanka, Kotiv villages) are characterized by a humus content of 2.3%, 2.2%, and 2.1%; easily hydrolyzable nitrogen content of 89, 89, and 106 mg/kg; a high content of available phosphorus of 167, 236, and 203 mg/kg; and a pH value ranging from 5.9 to 6.3. Podzolized slightly degraded chernozem soils of the Ostroh district (Ozhenyn village) are characterized by a humus content of 3%, an easily hydrolyzable nitrogen content of 137 mg/kg, a very high content of available phosphorus of 356 mg/kg, an available potassium content of 142 mg/kg, and a pH value of 6.6. In terms of microelement composition, the studied soils are assessed as follows: high content of boron and cobalt; medium content of manganese and sulfur; and low content of copper and zinc. According to the complex agrochemical score for 2011–2015, light gray forest soils were evaluated at 56 points, dark gray forest soils at 50, 53, and 62 points, and chernozem soils at 67 points. For 2021–2022, light gray forest soils improved their fertility and were again evaluated at 56 points.Dark gray forest soils in Zaborol and Rysvyanka increased their fertility levels to 52 and 55 points, while in Kotiv a decrease to 58 points was recorded. Chernozem soils in Ozhenyn also showed a reduction in fertility to 66 points. To maintain the high quality of podzolized chernozems in the long term, as well as to raise the medium quality to high in light gray and dark gray podzolized soils of the Ustia River basin, it is recommended to apply calculated rates of nitrogen and potassium fertilizers. This will eliminate first- and second-level nutrient deficiencies and increase the content of these elements in the studied soils to high levels. To increase the copper and zinc content in the soils, the use of nitrogen fertilizers such as ammonium sulfate (containing up to 500 mg/kg of zinc and 0.3–1.0 mg/kg of copper) and 40% potassium salt (containing 1–3 mg/kg of zinc and up to 10 mg/kg of copper) is recommended.