Studies on distribution of potassium fraction in surface and sub-surface layers of black soils

The potassium dynamics in black soils of maize growing areas of Haveri district, Karnataka was studied in UAS, Dharwad during 2016-17. 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 (529.53 kg ha-1 and 327.04 kg ha-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 2.83 to 8.13 mg kg-1 in surface with a mean of 4.60 mg kg-1. The water soluble potassium in sub-surface layer varied from 2.00 to 6.23 mg kg-1 with a mean of 3.67 mg kg-1. The black soils exchangeable potassium varied from 48.92 to 100.96 mg kg-1 in surface and 36.90 to 78.40 mg kg-1 in sub-surface. The trend of decrease in water soluble and exchangeable K was noticed in these soils from surface to sub-surface layers. The non-exchangeable potassium of black soils in surface samples varied from 566.37 to 790.84 mg kg-1. The non-exchangeable potassium varied from 622.17 to 865.43 mg kg-1 in sub-surface. The lattice potassium ranged from 1.38 to 2.03 per cent in surface layer and 1.53 to 2.07 per cent in sub-surface depth. The black soils total potassium ranged from 1.45 to 2.10 per cent in surface and 1.60 to 2.15 per cent in sub-surface layer.