Two-year studies were carried out at the Mallawi Agriculture Research Station Experimental Farm in Minia Governorate, Egypt, to study the effect of potassium sulphate, feldspar rock inoculated with releasing bacteria (RB) and without potassium fertilizer (control) as soil application and the spraying of four levels (0, 2.5, 5.0 and 10 g/L.)of licorice root extract on the  growth, production, quality and storability (evaluated over three storage periods; 0, 3 and 6 months ) of Allium cepa L (onion) plants, cultivar Giza 6. All the tested treatments improved the onion plant growth and yield comparing to control. Field treatment by licorice extract(LE) at 10 g/L alone or in combination with other treatments had a greater stimulatory effect, as well as the highest contents of nitrogen, phosphorus and protein were found in onion bulbs treated by 5 or 10 g/L. (LE) with no significant differences between the two concentrations. The potassium (K) content in onion plants was significantly greater with feldspar treatment than with potassium sulphate. Results revealed that the length of the storage period has a negative effect on bulbs composition and decreased their quality. However, field treatment by LE at 5 and 10 g/L. alone or combined with other treatments and feldspar inoculated with RB reduced the progressively decreasing trend together with maintaining some better chemical composition and desired properties (The maximum dry matter content (DM) %, nitrate content (No₃), total phenolic compounds (TPC), titratable acidity and the lowest moisture content) of the onion bulbs throughout long-term storage at room temperature.