MICRONUTRIENT UTILIZATION IN ONION (AND, OF COURSE, HOW THEY AFFECT FLAVOR)

W.M. Randle, T.W. Coolong, and P. Chang

Department of Horticulture, University of Georgia, Athens, GA 30606 USA Email: wrandle@uga.edu

The absorption and utilization of chloride (Cl) and zinc (Zn) were investigated in onion to better understand their requirements and tolerances, and to determine their effects on onion growth and subsequent flavor development. Chloride was varied from 0 to 500 ppm as CaCl2 in a greenhouse experiment. The plants were grown to maturity, the bulbs weighed and later analyzed for different flavor attributes. It was determined that the Cl requirement for onion is very high, and with adequate availability, Cl can be the fourth most utilized essential element in onion. As CaCl2 increased in the nutrient solutions, bulb weight increased by a factor of two, bulb S accumulation decreased by 45%, and bulb pungency decreased by 35%. Manipulating Cl may be thought of as a useful tool for managing high S environments for producing low pungency onion because of its strong effect on decreasing S uptake. In a separate experiment, Zn was supplied to onion seedlings at concentrations ranging from 10 to 150 ppm to investigate the rate of uptake in onion. Zinc uptake and accumulation occurred rapidly and proportional to the concentration in the nutrient environment when compared to S uptake. Within 24 h of applying the higher Zn rates, over 1200 ppm Zn measured in onion leaves on a dry weight basis. The concept of nutrient pulsing onions as a way of fortifying food for human consumption will be discussed.

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