Spatial Variability of Soil Potassium and its Relationship to Land Use and Parent Material

Information on the spatial distribution of plant nutrients is a prerequisite to predict their behaviour and to monitor the fertility in a watershed. This study was conducted to evaluate variations of plant available potassium (PAK) and non-exchangeable potassium (NEK) of a watershed with different land use and parent materials. Eight hundred soil samples were taken from 0-30 and 30-60 cm depths across the Kazova watershed of 20 656 ha in size. Average PAK was 152.8 mg/K kg in surface layers and 167.2 mg/kg in subsurface layers. NEK was 925 mg K/kg in surface and 167.2 mg K/kg in subsurface layers. All forms of K were the lowest in soils formed over serpentinite. Soils in pastures had the highest PAK and NEK. Both K forms were positively related to clay content. Spatial variability patterns of PAK and NEK were similar and consistent at both soil depths. The variation in parent material and land use is considered as the main cause for large variations of potassium forms.