Comprehensive Evaluation on soil Potassium in Some Cultivated Solils

The available status of soil potassium in some cultivated soils were comprehensively appraised by using Gapon coefficient (KG) and Q/I parameters (PBCk, ΔKo and ARGk) .The results showed that KG, PBCk, ΔKo and ARGk of the soils were significantly different with the composition of clay minerals.Soil samples 1, 2, 6 and 7 with predominant vermiculite and illite had high KG, PBCK and ΔKo but low ARke, which indicated that most of potassium in these soils were firmly retained on interlattice sites and difficult to be desorbed, so these soils showed strong potassium fixation and low potassium availability.Conversely, soil samples 3, 8, 9 and 10 with Kaolinite as dominant clay mineral had low KG, PBCK and ΔKo but high ARKe, which indicated that most of potassium in these soils were bound on planar sites with low selectivity to potassium and more easy to be desorbed, so these soils showed weak potassium fixation and high potassium availability, and the others (soil samples 4 and 5) with most abundant illite and sub-dominant Kaolinite showed intermediate potassium availability.