Resumo

VASQUEZ POLO, José Rafael; BAENA GARCIA, Diosdado  e  MENJIVAR FLORES, Juan Carlos. Spatial variability of physical and chemical properties in soils of the experimental farm in the Magdalena University (Santa Marta, Colombia). Acta Agron. [online]. 2010, vol.59, n.4, pp.449-456. ISSN 0120-2812.

We have studied the spatial variability of agricultural soils in the experimental farm at Magdalena University (Santa Marta, Colombia; 74° 07' - 74° 12' W, 11° 11' - 11° 15' N). Analyzed soil properties included: gravimetric soil moisture content, grain size analysis, bulk density, resistance to root penetration, hydraulic conductivity, organic matter content, pH, cation exchange capacity, total N and P, exchangeable cations (Ca⁺², Mg⁺², K⁺, Na⁺), metals (Cu, Zn, Fe , Mn) and B content. Sampling was based on a 29 x 29 m grid, resulting in 184 sampling points. Data analysis was done using univariate, multivariate and geostatistical approaches. The analyzed soil properties showed different degrees of variability: bulk density and pH low variability; grain size, resistance to root penetration, divalent exchangeable cations (Ca⁺² and Mg⁺²), Cu and B intermediate variability; while moisture content, hydraulic conductivity, organic matter content, monovalent exchangeable cations (K⁺, Na⁺), cation exchange capacity, Zn, P Mn and Fe a large variability. The geostatistical analysis revealed the presence of moderate spatial dependency, except for sand content, exchangeable Ca⁺², cation exchange capacity, P and Cu, which showed strong spatial dependency. The multivariate homogeneity index was low, being exchangeable Na⁺, B, Fe, K, pH and organic matter content the soil properties with lager contributions to heterogeneity. Classification analysis enabled to indentify four areas with similar edaphic conditions, which will allow to stablish the sampling strategy, number of samples, size and distribution of experimental units and thus to improve the implementation of agronomic management practices in agreement with the characteristics of the soils.

Palavras-chave : Spatial variability; physical and chemical properties; geostatistics; multivariate analysis and homogeneous zones.

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