Spatial variation features description of soil available P, K, Mg and soil pH by proportional effect

Abstract

This paper investigates the proportional effect of selected soil properties - how spatial variation changes are related to their local magnitudes (here standard deviations vs. mean). Content of available P, K, and Mg, and soil pH were analysed on nine agricultural fields of the Czech Republic. Firstly, strong direct within-field proportional effect based on Moving Window Statistics (MWS) was found for soil P and K, while Mg did not exhibit any clear proportionality. Soil pH showed indication of inverse proportional effect with high field-to-field fluctuations. The relationship strength of the effect was functionally related to the asymmetry (skewness) of distribution (r = 0.31 x skew 0.08). Secondly, between-field proportional effect of 9 surveyed fields, as a measure at different scale, showed generally parallel results with the MWS approach. Proportionality is therefore not scale dependent. However, slopes of linear relationships were different for the two scales. Finally, models for prediction of proportional variogram parameters were calculated. Correlation coefficients of relationship between semivariance parameters and mean proved that sill-nugget is more stable (r = 0.74 for P and 0.83 for K) than nugget (r = 0.30 for P and 0.53 for K).