Influence of Potassium and Sulphur Levels on Uptake of Nutrients in Onion (Allium cepa L.) and Residual Fertility of the Soil

A field experiment was conducted in black soil at Main Agricultural Research Station, University of Agricultural Sciences, Dharwad during Kharif 2009 to study the effect of potassium and sulphur on growth, yield and quality parameters of onion. The experimental design was split plot with 12 treatments [(Main plots K₀ - Control (No potassium), K₁ - K₂O @ 100 kg ha^-1, K₂ - K₂O @ 125 kg ha^-1, K₃ - K₂O @ 150 kg ha^-1, Sub plots - S₀ - Control (No sulphur), S₁ - S @ 15 kg ha^-1, S₂ - S @ 30 kg ha^-1) (Nitrogen and phosphorus levels were kept constant for all the treatments] and three replications. Higher contents of potassium and sulphur in leaf as well as bulb were observed with the higher levels of potassium and sulphur. The higher uptake of N (202.47 kg/ha), P (25.00 kg/ha), K (111.13 kg/ha) and S (43.24 kg/ha) were observed with 125 kg K₂O + 30 kg S per ha. In post harvest soil maximum available potassium (498.00 kg/ha) and sulphur (25.16 kg/ha) content was obtained in the treatment 150 kg K₂O plus 30 kg S per ha. Among all treatment combinations, fertilizer dose of 125 kg potassium and 30 kg sulphur per ha was found more remunerative in respect of net returns.