Variability of soil parameters in a uniformity trial on a Luvisol evaluated by means of spatial statistics

The relationships between soil parameters and indicators of soil genesis were investigated in a uniformity trial on Luvisol by means of classical and spatial statistics. The following properties were investigated in the topsoil (0-30cm) and subsoil (31-40cm): content of total carbon (C,), content of clay plus fine silt (FAT), concentrations of available potassium (K) and phosphorus (P), and pH values. The depth loamy Bt horizon and microrelief were considered as indicators of soil genesis. Smoothing of the raw data by means of block kriging eliminated the small scale variability of all parameters. In this way, the rank correlation coefficients between soil parameters increased by factor 2 and were to 0.52 for C-1-FAT, 0.69 for C-t-K, and 0.55 for C-t-P in the top soil. The maps for smoothed data allowed a much better visual analysis of spatial distribution of investigated properties compared to the raw data. The significant correlations as well as the similarity of maps and variograms suggested that the spatial variability of FAT, C, K, and P in the top soil was determined by the same factors. The depth of the loamy Bt horizon and the relief were the most important factors defining the distribution of the investigated soil parameters. The rank correlation coefficients of the smoothed and detrended relief with the soil parameters amount to -0.63, -0.77, -0.71, and -0.57 for FAT, C-t, K, and P, respectively.