Evaluation of extractants and critical levels for potassium in wheat

The present study was undertaken to evaluate a suitable extractant for available K for subtropical soils of Jammu region. Six extractants viz.; 1 N NH₄OAc, 1.38 N H₂SO₄, 1 N HNO₃ (boiling), Morgan's reagent, 0.01 M CaCl₂ and distilled water were tested on twelve representative soils differing in available K. Graded doses of K (0, 6, 12, 18 mg kg⁻¹) were applied to wheat (PBW-373) in low, medium and high K soils. The extracted K varied widely with a range of 9–1566 mg kg⁻¹ by different extractants. Maximum amount of K (1566 mg kg⁻¹) was extracted by boiling 1 N HNO₃ in Reasi soil whereas 0.01 M CaCl₂ extracted the minimum K (9 mg kg⁻¹) from R.S. Pura soil. A positive relationship existed between 1 N NH₄OAc and 1 N HNO₃ with all other extractants except that 1 N HNO₃ did not show relationship with distilled water. The critical limits of soil K extracted by NH₄OAc, H₂SO₄, HNO₃, Morgan's reagent, distilled water and CaCl₂ were 82, 82, 870, 41, 44 and 19 mg kg⁻¹, respectively. The critical K limit for plant K was observed to be 1.25 and 1.8 per cent at 46 and 60 days of crop growth, respectively.