Nonexchangeable Potassium, Clay Mineralogy and Specific Surface Area Interactions in Kazova Soils
Hikmet GUNAL, Fevzi AKBAS, Nurullah ACIR
Gaziosmanpasa University, Faculty of Agriculture, 60240 Tokat, Turkey
Plant available and non exchangeable potassium contents, clay mineralogy and specific surface area of soils collected from Kazova Plain (20.656 ha) located in Tokat Province were analyzed and mapped. Thus, areas sensitive to potassium fertilization were determined. “Random sampling method” was used to determine the sampling locations. Geostatistical techniques were used to identify the variability of soil properties and prepare the related maps. Soils, lowest in potassium content occurred in the areas adjacent to Yesilirmak River. Soils developed over serpentine schist colluvial materials located in left side slopping areas possessed the lowest reserve and exchangeable potassium levels. Soils located in right side sloppy areas formed over calcareous colluvial deposits contained the highest potassium content. Average plant available potassium content was 30.13 kg K/da and reserve potassium was 186.5 kg/da. However, more than half of the soil samples collected in the study area didn't contain enough available potassium to sustain the plant growth without any yield loss. The dominant clay minerals in the study area were smectite, illite and kaolinite, respectively. Co-kriging spatial interpolation method was used to predict the mineralogy of soil samples those were not analyzed for mineralogy. Cation exchange capacity and the reserve potassium had the highest correlation with clay types. No significant relationship was obtained between specific surface area and clay minerals. While, a statistically significant (P<0.01) relationship was occurred between specific surface area and cation exchange capacity.
Keywords: Reserve/unexchangeable potassium, plant available potassium, clay mineralogy, illite, geostatistics, surface area, co-kriging.