Physicochemical and Structural Properties of an Oxisol under the Addition of Straw and Lime

Abstract

Core Ideas Liming represents a common agricultural practice for abating soil acidity. High doses of lime on the Oxisol surface increases the electronegativity of the soil system. High electronegativity increases clay dispersion in the uppermost soil layer. Clay migration led to a series of physical alterations in soil subsurface layers. Overliming can lead to the degradation of highly weathered soil structures. Liming represents a common agricultural practice for abating soil acidity. Nevertheless, elevated amounts of agricultural lime in Oxisols, with or without cultural residue addition, could alter soil physicochemical properties and impact soil structure. In this context, the physical, chemical, and structural behaviors of an Oxisol under the addition of lime and straw were assessed. Lime doses (0, 3.9, 7.8, and 15.6 Mg ha–1) were either applied on the surface or incorporated into the 0‐ to 5‐cm soil layer. Straw applications followed the same procedure with quantities of 0, 4, 12, or 16 Mg ha–1. The effects on the soil profile were evaluated through physicochemical (specific surface area, ζ potential, and pH), physical (density, penetration resistance, water dispersible clay, and total porosity), and micromorphological properties (surface area, volume, connectivity, size, and pore anisotropy) 1 yr after soil incubation in polyvinyl chloride cylinders 30 cm long and 14.5 cm in diameter. Lime application on the surface or into the 0‐ to 5‐cm layer increased soil pH to values above 7.0 and the electronegative potential of soil colloid surface, promoting clay dispersion. Water‐dispersed clay migrated in the soil profile, causing pore obstruction, and higher soil density and penetration resistance. In addition, excessive lime decreased specific surface area, anisotropy degree and the connectivity of the soil pore system. Straw addition promoted a slight increase of colloids electronegative potential but did not alter soil physical properties.