Resumo

VAZQUEZ, Mabel et al. Dynamics of soil liming materials broadcast on a thaptoargic hapludoll soil in Argentina. Cienc. suelo [online]. 2013, vol.31, n.1, pp.23-32. ISSN 1850-2067.

Soils of temperate Argentine pampas have been undergoing a gradual acidification due to the application of nitrogen fertilizers without replacement with basics nutrients. Although liming has been widely adopted, the acidification process is difficult to revert in depth under no-tillage systems. The aims of this study were to evaluate the effect of surface-applied gypsum added to calcitic and dolomitic limestones on the downward movement of HCO^{3 -}/Ca²⁺/Mg²⁺, the cation exchange capacity (CEC) and the actual/potential acidity on a Thaptoargic Hapludoll. The following treatments were assigned to undisturbed soil columns (20 cm): control (C0), 1000 kg ha^-1 CaCO³ (C1000), 1000 kg ha^-1 of a mixture of CaCO³/MgCO³ (D1000), treatment C1000 + 500 kg ha-1 CaSO4.2H2O (C1000g) and treatment D1000 + 500 kg ha^-1 CaSO₄.2H₂O (D1000g). Water (6.8 mm) was applied weekly and leachates were collected during 16 weeks. The soil was divided into three depths for analysis. The presence of Ca²⁺/Mg²⁺ in depth both in absolute numbers and proportionally to the amount added was greater in D1000, C1000g, and D1000g compared to C1000 and the control. CEC and the Ca:Mg ratio increased in C1000 at the 0-13 cmdepth, which would reflect a greater Ca availability in the short term. The amendments generally increased the actual/ potential pH, as well as the exchangeable Ca²⁺/Mg²⁺ concentrations at all depths, but the increases were always greater in the 0-6.5 cm soil layer. Gypsum addition increased the downward movement of liming materials after 16 weeks and is recommended in no-tillage scenarios.

Palavras-chave : Dolomitic and calcitic limestones; Calcium sulphate; Gypsum; Leaching.

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