Resumo

LA MANNA, Ludmila et al. Walter holding capacity of volcanic soils estimated by easily measured variables. Cienc. suelo [online]. 2018, vol.36, n.1, pp.23-29. ISSN 1850-2067.

Soils in Patagonian Andean Region are developed mainly from volcanic ashes and they have distinct properties. We aimed to develop models in order to estimate Field capacity (FC) and Permanent Wilting Point (PWP) in volcanic soils, using easily measured variables: soil textural class and Fieldes test, which allows detecting non-crystalline aluminosilicates. Data were analyzed with second order regression models, considering textural class as ordinal independent variable (x) and FC and PWP as dependent variables. The following regression models were developed: For soils with negative Fieldes test (i.e., without non-crystalline aluminosilicates) (N = 132): FC = 47,18 - 4,09 * x + 0,13 * x² (R² = 0,52) PWP = 30,46 - 3,52 * x + 0,13 * x² (R² = 0,53) For soils with positive Fieldes test (i.e., with non-crystalline aluminosilicates) (N = 211): FC = 35,50 + 1,26 * x - 0,23 * x² (R² = 0,25) PWP = 21,53 + 0,29 * x - 0,13 * x² (R² = 0,37) x = code for textural class: 1 = clay; 2 = silty clay; 3 = silty clay loam; 4 = sandy clay; 5 = clay loam; 6 = silt; 7 = silt loam; 8 = sandy clay loam; 9 = loam; 10 = sandy loam; 11 = loamy sand; 12 = sand. These models showed significant fit, and are a useful tool based on readily available field data.

Palavras-chave : Field capacity; Permanent Wilting Point; Texture; Andisol.

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