Distribution of different forms of soil potassium in surface and sub-surface layers of paddy growing areas of Nagpur District

The potassium dynamics in black soils of paddy growing areas of Nagpur district, Maharashtra was studied during 2018-19. Potassium exists in soil in different forms such as water soluble, exchangeable, non-exchangeable, lattice K. The available potassium on an average obtained highest in both the depths (190.75 mg kg-1 and 173.43 mg kg-1 in surface and sub-surface depths, respectively). The surface samples recorded high available potassium compared to sub-surface layer. The water-soluble K of black soils ranged from 5.10 to 8.10 mg kg-1 with a mean of 6.75 mg kg-1 in surface depth. The water-soluble potassium in sub-surface layer varied from 3.90 to 7.70 mg kg-1 with a mean of 6.21 mg kg-1. In the black soils, exchangeable potassium varied from 139.76 to 217.25 mg kg-1 in surface layer and in sub-surface layer it varied from 120.84 to 207.29 mg kg-1. The trend of decrease in water soluble and exchangeable potassium was noticed in these soils from surface to sub-surface layers. The non-exchangeable potassium of black soils in surface samples varied from 673.13 mg kg-1 to 789.50 mg kg-1. The non-exchangeable potassium varied from 628.12 mg kg-1 to 778.00 mg kg-1 in sub-surface. The lattice potassium ranged from 5316.40 mg kg-1 to 7324.64 mg kg-1 in surface layer and 6013.73 mg kg-1 to 7241.60 mg kg-1 was observed in sub-surface depth. The black soils total potassium ranged from 6250 to 8322 mg kg-1 in surface and 6900 to 8140 mg kg-1 in sub-surface layer.