Agrochemical characteristics of mountain soils of the Fergana Valley

The relevance of examining the soils of the Fergana Valley is due to their diversity and importance for the agriculture of the region. Different soil types differ in their granulometric composition, fertility, and ability to retain moisture, which affects their agrochemical properties. The purpose of the study was a comprehensive analysis of the agrochemical characteristics of the soils of the Fergana Valley, including granulometric composition, humus content, acidity, carbonate content, water properties, and biological activity. The methods included field research, sampling from different altitude zones, and laboratory chemical composition analyses. Nitrogen was determined by the Kjeldahl method, phosphorus – the Machigin and Kirukov method, and potassium – flame photometry. The results of the study showed substantial differences in the composition and properties of different types of soils. Brown forest soils demonstrated the most favourable agrochemical parameters. The granulometric composition of brown forest soils is medium loamy, with a sand content of 35-45%, silt of 30-40%, and clay of 15-25%. High levels of humus (4.5-6%), total nitrogen (0.2-0.3%), available phosphorus (20-40 mg/kg), and potassium (high levels) were recorded in the soils. The biological activity, estimated by microbial abundance, was 2-4 million/g, which confirmed the high metabolic activity of the soil microflora. Mountain-brown carbonate soils were characterised by a heavier granulometric composition, with an increased clay content (25-35%) and moderate fertility rates: 2.5- 4% humus, 0.1-0.2% nitrogen, 10-25 mg/kg of phosphorus, and a medium potassium level. Sandy soils have low moisture capacity, weak aggregate structure, and extremely low fertility rates: 0.5-1.5% humus, <0.1% nitrogen, 5-15 mg/kg phosphorus, and low potassium levels. Biological activity does not exceed 1 million/g. The acidity of soils varied: brown forest soils have a slightly acidic or neutral reaction with a pH of 5.8-6.5, which is favourable for the absorption of nutrients. Mountain-brown carbonate soils are alkaline with a pH of 7.5-8.2, which reduces the availability of certain elements. Sandy soils have a slightly alkaline pH of 6.8-7.4. The data obtained can optimise land use, increase soil productivity, and minimise soil degradation