Effects of Sulphur and Number of Foliar Application with Complete Micronutrient Fertilizer on Yield and Quality of Two Onion Cultivars

An experiment was cobducted during two years 2002 and 2003 in Neishabour, to study the effects of sulphur and micronutrient fertilizer on yield and quality of onion. The experiment was in split plot factorial form in complete randomized block design with three replications. Two onion cultivars (Ghermez Azarshahr and Sefid Qom) were arranged in main plots and different sulphur amounts (0, 150, 300 and 450 kgha-1) and number of foliar applications with complete micronutrient fertilizer (0, 1, 2 and 3 sprayings with 6/1000 concentration) in subplots. Each plot was six meter long with 30cm row distance. The results of combined analysis of variance on data showed the ratio of height/diameter of onions, number of storage leaves, concentration of sulphur and nitrogen (NO3-) in two cultivars were not significantly different, but neck thickness, number of multiple growing points, potassium, Manganese and copper concentrations were affected by experimental factors. Interaction effects of year×cultivar showed significant differences between bulb yield and number of multiple growing points, number of edible layers and copper concentration. Application of 450 kgha-1 sulphur (with Thiobacillus bacterium) and two foliar micronutrient fertilizer resulted in the highest concentration of potassium of bulbs in all treatments. Bulb yield was affected by year, cultivar and sulphur fertilizer amount, but number of foliar applications had no effect on bulb yield. Application of 150 kgha-1 sulphur fertilizer decreased nitrate concentration in bulbs, but two foliar applications of micronutrient fertilizer increased significantly the concentration of nitrate in bulbs of cultivar Ghermez Azarshahr (195.4 ppm). Foliar application of micronutrient fertilizer and 450 kgha-1 sulphur fertilizer decreased nitrate concentrations of bulbs significantly.