CHANGES IN PUNGENCY OF ONIONS BY SOIL TYPE, SULFUR NUTRITION AND BULBMATURITY

'Texas Grano 1015Y' onions were grown in two commercial fields with cl ay or loam soil with or without an excess sulphur (22.4 kg S ha(-1)) t reatment. Onion bulbs were harvested every one or two weeks from March until bulb maturity and enzymatically produced pyruvic acid, dry matt er, total sulphur in bulbs and sugar content were measured. Additional sulphur nutrition had no significant effect on any of the parameters. Total sulphur content in the bulbs was not influenced by S nutrition or soil type. Onions grown in loam soil were slightly higher in sugar content. Pyruvic acid, dry matter content and sugar content all decrea sed at the second sampling date and gradually increased as bulbs matur ed. This study indicated that pungency and sugar content of onions can not be significantly changed by choosing the field or applying extra s ulphur nutrition in a commercial field containing sufficient levels of sulphur or irrigated with water of high sulphur content. (C) 1998 Els evier Science B.V.