Redistribution of Exchangeable Calcium, Magnesium, and Aluminum Following Lime or Gypsum Applications to a Brazilian Oxisol

Abstract A greenhouse experiment was carried out with 16 columns of an undisturbed Oxisol that had sufficient subsoil acidity to restrict root growth of a wide variety of crop plants. The objective was to determine the effects of surface applied CaCO 3 , CaSO 4 ·2H 2 O, and water on subsoil pH and exchangeable Al, Ca, and Mg. Eight soil columns were treated with CaCO 3 or CaSO 4 ·2H 2 O at rates equal to 0.25 and 1.50 × the lime equivalent (KCl‐extractable Al). The irrigation treatments consisted of trickle irrigation applied at 8.94 and 17.88 mm day −1 for 6 months. These treatments were superimposed on the amendment treatments. Observations included volume and composition of drainage water during the course of the experiment and chemical composition of the soil column by depth increments once the irrigation treatments were completed. Soil analysis included pH, cation exchange capacity (CEC), exchangeable cations, and composition of saturation extracts of soil. Effects of CaCO 3 treatments were observed only in the upper 20 cm of the profiles irrespective of irrigation and fertilizer treatments. The CaCO 3 treatments increased soil pH, CEC, and exchangeable Ca while decreasing exchangeable Mg and exchangeable Al; and CaSO 4 ·2H 2 O treatments reduced the level of exchangeable Al and Mg throughout the 100‐cm depth profiles while increasing the level of exchangeable Ca. Soil pH and CEC were unaffected by the latter treatment. Based on the effectiveness of CaSO 4 ·2H 2 O in reducing exchangeable Al and Mg while increasing exchangeable Ca, the combination of dolomitic lime and gypsum appears to be an appropriate amendment treatment for Oxisols with toxic concentrations of available Al.