Onions - Queensland style, are mild onions the future?

Abstract

A total of 245 onion cultivars from different seed sources were evaluated in trials conducted from February 1994 to June 2001, in Queensland, Australia. Seeds were sown fortnightly from late February until mid-June in 1994 and 1995. Subsequent to these, seeds were sown at monthly intervals from March until June from 1996 to 2001. Different planting methods were used including direct sowing using air-sowers, cone planters, transplanting and seed taping. Seed taping proved to be very successful in achieving uniform bulb size and shape due to very accurate plant spacing. Transplanting achieved a very similar result but at a much greater cost and proved to be uneconomical. Data were recorded for marketable yield and bulb quality (especially pungency), but only data from 1999 to 2001 are presented in this paper. In 1999, the highest yields were obtained in May from cultivars of Nautilus (Yates) and Columbus (SPS). Both cultivars produced marketable yields in excess of 45 t/ha. In 2000, no cultivars were supplied for either early sowing dates (March and April). Cultivars sown in May produced the highest yields, with Sombrero (Henderson) and Predator (Yates) recording the highest yields of 90.4 and 92.2 t/ha, respectively. In 2001, sowing in June gave the best yield results. The Yates cultivars Predator and K5156 produced marketable yields of 86.1 and 110.0 t/ha, respectively. Henderson's Sombrero produced a high marketable yield of 78.3 t/ha. In May sowing, the Yates cultivar J5114 also achieved a marketable yield in excess of 90 t/ha. Analysis of pyruvic acid concentration, a measure of pungency of an onion, showed that only a small number of cultivars tested had a pyruvic acid level of less than the USA standard. Only Sombrero recorded an acceptable pyruvic acid level in 1999, 2000 and 2001, and is thus considered as a high-quality mild onion cultivar.