Soil Chemical and Physical Properties on an Inceptisol after Liming (Surface and Incorporated) Associated with Gypsum Application

Inceptsoils have high aluminum contents, and amendments are required to ensure a satisfactory crop development. Liming is efficient in neutralizing Al3+, but when applied to the topsoil its action is restricted to the surface layers, and sometimes lime incorporation into the soil is recommendable. However, tillage may negatively alter physical soil properties. Thus, gypsum could be an alternative to increase Ca2+ levels and reduce Al saturation in deeper layers, without requiring tillage. An experiment was initiated in 2010, to assess chemical and physical soil properties. Soil samples were collected in February 2013. A random block design with sub-subplots and two replications was used. Lime was applied to the surface of the main plot (0, 8 and 16 Mg ha(-1)) and incorporated into the soil by plowing and light harrowing. Gypsum was applied to the subplot (0 and 6 Mg ha(-1)), and the sub-subplots corresponded to the sampled layers (thickness of 0.05 m, to a depth of 0.25 m). The following parameters were evaluated: pH in water, base saturation, Al saturation, Ca2+, Mg2+, soil organic matter, water retention, and least limiting water range (LLWR). Lime incorporated into the soil reduced Al3+ and increased pH and Ca2+ levels, especially in the deeper soil layers, although pH levels did not exceed 5.1 and base saturation was lower than 60 %, still inadequate for crops. The gypsum rate of 6 Mg ha(-1) did not decrease Al saturation, but reduced Mg2+ levels in top soil layers. Soil water retention and LLWR were not affected by plowing and harrowing within a period of three years. Gypsum rates below 6 Mg ha(-1) were not effective in reducing Al saturation and increasing Ca2+ levels. Incorporated lime is more effective in correcting the acidity of the soil profile and, after three years, soil water retention and LLWR were similar under both liming methods.