The Influence of Slope Exposure, Profile Depth and Erosion Processes on Changes in the Content of Potassium, Phosphorus and Humus in Brown Soils of Mountain Pastures of Uzbekistan

Abstract

Humus, potassium, and phosphorus are key components of soil that play crucial roles in ecosystem productivity, plant growth, and development. They control a wide range of processes, including greenhouse gas fluxes, nutrient cycling, infiltration, and water retention. This article presents the results of evaluating humus, potassium (K), and phosphorus (P) content in the profile of brown soils in mountain pastures of Uzbekistan, as well as their distribution within these soils. The brown soils studied in the mountain pastures of Uzbekistan have a loamy granulometric composition, with the clay fraction not exceeding 20%. The carbonate content is low (2.5-9%), with the maximum amount found in the carbonate horizon. The soils exhibit weak leaching. The total humus content in the upper horizon varies from 1 to 6.6%. It was observed that the soils on the more moistened northern and western slopes contain more humus than those on the southern and eastern slopes, indicating a dependence of high humus content on slope exposition. For the first time, the article allocates phosphorus and potassium of near, labile, and potential reserves (as a percentage of the total content) to estimate the change in the nature of brown soils under economic use. It was found that the potential reserve of phosphorus and potassium (35.5-90%) prevails in soils. Further study of the features of humus, potassium, and phosphorus, their accumulation, and restoration in brown soils is essential for developing recommendations for the rational use, anti-erosion protection, and increased productivity of mountain pastures in Uzbekistan.