Potassium fixation capacity of surface soils under different land use systems.

摘要

This study was conducted in Navile, Shivamogga, Karnataka, India to examine the potassium fixation capacity of soils under different land use systems. Twenty-five surface soil samples (five soil samples in each land use system) at 0-20 cm depth were collected from different land use systems viz., agri-system (rice and tobacco), horti-system (arecanut), silvi-system (eucalyptus) and current fallow land use system (control). The water soluble potassium content in surface soils varied from 10.06 to 16.66 mg/kg. Among all the forms of potassium, water soluble potassium was the least dominant fraction. The exchangeable potassium content in surface soils varied from 50.1 to 152.6 mg/kg. The content of mineral potassium in surface soils of different land use systems varied from 0.77 to 1.59%. The contribution of this form to total potassium was maximum compared to other fractions as this fraction includes potassium from potassium- bearing minerals. The content of total potassium in surface soils varied between 0.82 to 1.62%. The results also revealed that the potassium fixation capacity of these soils varied widely. The agri-system (rice) recorded the lowest potassium fixing capacity (0.22 cmol(p)/kg), while the silvi-system (eucalyptus) recorded the highest potassium fixing capacity (0.76 cmol(p)/kg). It is evident that the wide variation in capacity of the land use systems to fix the added potassium is mainly due to the potassium saturation of exchange complex of the soils, nature and amount of clay minerals. Among the five different lands use systems studied, the soils under silvi-system and current fallow land use systems recorded higher potassium fixation capacity than the soils under cultivated land use systems.