Allium & Brassica Centre joint managing director Andy Richardson made the announcement to delegates at this year's Onion & Carrot Conference in Peterborough on 18-19 November.
He revealed that ideal harvesting conditions had meant that the quality and storage potential of spring drilled reds and browns was "excellent"
- with pack-outs for drilled crops expected to be between five and ten per cent up on last season.
Yields are also above average at around 48 tonnes per hectare, giving the UK a production value of just over 390,000 tonnes, he added.
"The biggest impact on production area since 2004 has been the effect of the two exceptionally wet summers of 2007 and 2008," said Richardson.
"High yields, coupled with relatively poor quality and a high level of internal issues, had a significant effect on grower returns.
"In stark contrast, the dry August and September of 2009, while slightly reducing yield potential, has led to some of the best quality seen in onion stores over the past 20 years and with relatively low levels of internal issues pack-outs are expected to be good.
"The 2009-10 season will undoubtedly be a better year in terms of profitability than 2007 or 2008."
However, Richardson revealed that UK bulb onion production area is at its lowest level in 15 years due to the "significant pressure" the industry has endured over the past five years. It has slumped from a peak production area of 10,360ha in 2004 to 8,288ha in 2009.
He added that there had been a ten per cent drop in acreage over the past year, yet the acreage has dropped to a level between 8,000ha and 8,500ha, which "history shows is currently a sustainable production area for the UK".
Looking to the next decade, Richardson warned growers that they will face continued threats from imports. Bulb onion imports, he said, are rising rapidly - having already increased from approximately 240,000 tonnes in 2004 to 325,000 tonnes in 2008.
The Netherlands is the UK's largest source of imports, bringing in just over 100,000 tonnes in 2008. It is closely followed by Spain, which exported just under 100,000 tonnes to the UK in the same year.
Richardson argued that the UK's relatively high production costs pose a threat to the industry, as does the weather in Britain, which is cooler, wetter and more unpredictable than that of continental Europe.
Changes to European pesticide legislation, as a result of the revision of Directive 91/414, are also expected to affect growers, he added. Ramrod, Dacthal, Stomp, Totril, Afalon, Dithane, Invader, Valbon and Fubol Gold are expected to be taken off the shelves.
But on a positive, note Richardson said British growers have many advantages over their competitors. They are "technically excellent", have a strong R&D base and are lucky to have a diverse range of soil types and production areas to help spread the risk, he explained.
"Onion growing in the UK is a challenge and it won't get any easier over the next five to ten years," he added. "However, our industry is the envy of other onion-producing countries both in the EU and worldwide."