Fractionation of micronutrient cations in a selected Saudi Arabian soil subjected to different tillage practices

Abstract

Abstract Sustaining or increasing soil micronutient availability depends in part on soil tillage practices that alter soil properties, such as soil organic matter, pH, and cation exchange capacity. The main objective of this study was to determine the effect of various tillage systems on the distribution of the species of micronutrient cations in soil. Soils were sampled from the 0‐ to 20‐cm depth from three conservation practices (no‐tillage (NT), harrowing (HR), and chisel (CH)) and two conventional tillage systems (moldboard (MB) and disking (DS)). Soil samples were fractionated sequentially to determine Zn, Cu, Mn, and Fe in the following species: exchangeable, organic, occulted (Mn oxide, amorphus Fe oxide, crystalline Fe oxide), and residual forms. Conservation tillage systems (HR, CH, and NT), had a significant effect on the distribution of Zn, Cu, Mn, and Fe in exchangeable and organic forms compared to the conventional tillage systems (DS and MB). The conservation systems increased Zn and Fe in the exchangeable and organic form, and decreased Zn in the occulted form (amorphous Fe oxide fraction). Copper in the organic form was higher but its occulted form was lower (in the amorphous Fe oxide fraction) for conservation tillage systems compared to conventional systems. Manganese was higher in the organic fraction but lower in its occulted (amorphous Fe oxide) and residual fractions for conservation versus conventional tillage. Iron in the exchangeable and organic forms was higher, whereas Mn oxide and crystalline Fe oxide fractions were lower in conservation tillage than in conventional tillage systems. It appears that conservation tillage practices transformed Zn, Cu, Mn, and Fe from residual and occulted forms (amorphous Fe oxide, Mn oxide, and crystalline Fe oxide) to species of the exchangeable, organic, or Mn oxide fractions.