Influence of NH4NO3 and K2SO4 on qualitative characteristics of onion

A pot experiment was conducted to investigate the effects of ammonium nitrate and potassium sulfate on qualitative characteristics of onion (Allium cepa L. cv. Azar Shahr). The experiment was arranged as a randomized complete block design with four replications. Treatments were consisting of NH4NO3 (50, 100, 150 and 200 mg/kg) and K2SO4 (0, 175 and 350 mg/kg). The results showed that pyruvate content of onion bulb was improved with applications of 200 mg/kg ammonium nitrate and 350 mg/kg potassium sulfate. Total soluble solids (TSS) were increased as a result of using 175 mg/kg potassium sulfate. Moreover, increasing ammonium nitrate led to decreasing of total soluble solid content (%) and vitamin C. However application of higher amount of potassium sulfate up to 350 mg/kg increased the vitamin C content. Bulb ash weight showed a decreasing trend with increasing of potassium sulfate and ammonium nitrate. The percentage of dry matter increased with the applications of potassium sulfate and ammonium nitrate up to 350 mg/kg and 100 mg/kg, respectively.

► In this work, we studied the relation of nitrogen and sulfur nutrition on onion bulb quality characteristics.
► The data of experiment indicated positive correlation between bulb sulfur content and bulb vitamin C concentration and onion pungency.
► There was negative correlation between bulb nitrogen concentration and vitamin C content.