Properties of Waterlogged Soils Developed on Arkose and Aeolian Sands in an Agro-Silvopastoral System

Abstract

Globally speaking, academic research assumes that soils affected by water stagnation have a significant constraint, especially concerning their productivity and environmental benefits. In the surrounding landscape of northern Ávila Province (northern Spanish Central System), where many small farmers and livestock breeders of the region live, there are areas that are periodically flooded. This study examines the impact of hydromorphism on soil features and formation in La Moraña, a region with arkosic and aeolic sands; it also investigates the soil's role in sustainable waterlogged agro-silvopastoral development. The main land uses are agriculture, pastures or pine forests. The soils show acidic to alkaline reaction (pH 5.6 to 9.1), with sandy to loamy textures, and contain moderate to high levels of organic matter (1.7% to 8.0%) and total nitrogen (0.01% to 0.26%) contents. A moderate to medium cation exchange capacity (CEC) (3.13 to 15 cmol kg⁻¹) and high base saturation status (72% to 81%) were observed. In both soil groups (Cambisols and Arenosols), the predominant soil cations were Ca²⁺ (0.7 to 25.7 cmol kg⁻¹) and Na⁺ (0.19 to 9.5 cmol kg⁻¹), while K⁺ was present in minor amounts. Given the nature of the original material, although the carbonate content of the parent material lay below the detection limit, high carbonate contents greater than 25% were observed in certain horizons (Bkg of profiles 1 and 2). Weak gleization was observed in all profiles, with grey colours (light to dark) in the subsurface horizons, denoting some effects of iron reduction, resulting from a dual action of pluviometry and a practically flat topography; and occasionally flooding or water-table rise. In addition, hydromorphic conditions can also develop due to soil compaction. So, the major soil-forming processes are accumulation of organic matter and brunification in drained conditions. While litter formation in conditions of high moisture, and weak gleization against excessive moisture are the dominant processes. La Moraña's soils stay productive through agroforestry and crop rotations, preserving their potential despite their hydromorphic nature.