Knowledge of the spatial variability of the content and transformations of soil nutrients is important for precision agriculture and environmental protection. Spatial patterns of exchangeable (Na-Exch, K-Exch) and water soluble (Na-WS, K-WS) forms of sodium and potassium were examined in Luvisol soil lying in the region of Cuiavia and Pomerania, northwest Poland, so as to identify their spatial distribution for the implementation of site-specific management. In April 2007, soil samples were collected in a system of 10 x 10 m grids (n = 50) from an area of 0.5 ha located in an intensively used arable field. Water soluble forms of Na and K were determined after extraction with distilled water in a 1:5 soil to water ratio, while the exchangeable forms of these elements were assayed in 0.1 M BaCl2. The data were analyzed both statistically and geostatistically from semivariograms and their modelling. The spatial autocorrelation of a data set is described with the Moran’s I correlograms, hence adequate correlograms were drawn. Among all the properties determined, it was only water soluble K that showed significant spatial autocorrelation. Other soil properties (Na-WS, Na-Exch, K-Exch) did not demonstrate any spatial autocorrelation (the Moran’s I values were close to zero at p < 0.05), which indicated their random spatial variability. In order to assess the spatial variability of K-WS, a spherical model with the nugget effect was fitted into the calculated semivariogram. The results were assigned to the moderate variability class (the nugget effect 52%), and the range ofthe spatial impact stretched for 38 m.

19.2.2014