Soil Potassium Fractions and Response of Cauliflower and Onion to Potassium

Two hundred soil samples collected from Agra district were analyzed for their potassium fractions. The lattice, HCl soluble, fixed, exchangeable and water soluble K contributed 60.4, 29.6, 9.3, 0.64 and 0.06% towards total soil K in these soils. Highly significant positive relationships amongst various fractions of soil K indicated existence of a dynamic equilibrium between different forms of K. Vegetable crops responded significantly to potassium up to 90 kg K₂O ha⁻¹. The content and yield of protein in both the crops increased significantly with the addition of potassium. The maximum net return of Rs. 1, 46, 468 and 98, 752 and B:C ratio of 2.24 and 1.55 were recorded in cauliflower and onion, respectively with 120 kg K₂O ha⁻¹. Nitrogen uptake by cauliflower and onion progressively increased from 103.8 to 165.5 and 45.2 to 70.0 kg ha⁻¹, respectively with application of 120 kg K₂O ha⁻¹. The uptake of P, K and S by both the crops also increased with graded levels of potassium. Percent utilization of added K by cauliflower and onion was maximum with 60 and 90 kg K₂O ha⁻¹, respectively.