The paper outlines a concept related to selecting a site for experimental purposes. Selection of an experimental plot most frequently relies on performing visual evaluation of a given site, followed by the establishment of a field trial. In general, the question of geochemical variability is ‘intentionally’ postponed! Verification of this approach has been undertaken, testing such parameters as soil pH and exchangeable aluminum (Alex) versus spatial (investigated area, 12 672 m2) and downward (sampling depths, i.e., 0-20, 20-40 and 40-60 cm) distribution. Winter wheat biomass at tillering (BBCH29) and grain yield at harvest (BBCH99) were additionally considered. The results have revealed that pH values fluctuated between 3.6 and 4.4 with respective coefficients of variation (CV) ranging from 3.10 to 5.92%. The concentrations of Alex ranged from 38.0 to 144.9 mg kg–1, corresponding to CV within 28.34 and 44.03%. The variograms and geostatistical maps have demonstrated the spatial as well as downward variability of these parameters. The spatial distribution of plant biomass followed quite closely the exchangeable aluminum (Alex) levels, which implies that natural soil parameters such as Alex are not easily compensated for by agricultural practices, for instance nitrogen application. The spatial grain yield – Alex dependence which emerged at harvest confirmed the variability observed at tillering (BBCH29). Thus, the spatial variability of pH, Alex and wheat biomass as well as grain yields (BBCH99) verified the approach to selecting an experimental site. It was demonstrated that selection of a research site on the basis of its appearance and shape alone may lead to misinterpretation of experimental results.

17.2.2012