Effect of Ammonium Nitrate and Potassium Sulfate on Concentration of Some Nutrients in Onion

Nitrogen is a key nutrient in plant growth and it is necessary for amino acid synthesis. Sulfur has very important role in the biosynthesis of the Alliums flavor and pungency precursors and Potassium improve crop yield and quality. In order to study the effect of ammonium nitrate and potassium sulfate on concentration some of the mineral elements in onion (Allium cepa L. Azar Shahr cv.) a pot experiment was carried out with two factors, comprised nitrogen and sulfur, in a randomized complete block design with four replications. Nitrogen and sulfate were supplied as NH4NO3 (50, 100, 67.5 and 90kg ha-1) and K2SO4 (0, 78.3 and 156.6 kg ha-1) respectively. Three 8 weeks old onion seedlings were transplanted to pots with 7 kg soil as a experimental unit so, 144 plant were performed in 48 pots. At bulbing stage, one plant were sampled per pot and N, P, K and S concentration in leaves were determined and after bulb harvesting, also N and S in bulbs were measured. The result indicated that, by increasing K2SO4 to 156.6 kg/ha P, K and S concentration in leaves and bulb increased, however the highest N concentration in leaves and bulb were observed by application 78.3 kg/ha K2SO4. Increasing trends in leaves and bulb N and leaves K were observed by 67.5 kg/ha NH4NO3. In conclusion, by considering of nutrient absorption and dry matter production 156.6 kg/ha K2SO4 and 67.5 kg/ha NH4NO3 for better onion bulb production is recommended.