When the spring-sown bulb onion demonstration plots were drilled in drizzling rain at Raker Farms near Croxton in Norfolk on 16 March, little did National Institute of Agricultural Botany (NIAB) staff know that it would not rain again for at least a couple of months.
"This is the third year I've said it's been a dry spring, so maybe this is the norm now," says NIAB vegetable specialist Bruce Napier. "Sowings started well in the warmer conditions but struggled with the dryness." Plots were irrigated by rainguns to the same schedule applied to the commercial crop alongside. "A few bolters are coming through now, in August, where plants have been stressed, but it's an annoyance rather than a problem," he adds.
The dry conditions seem to have upset the normal run of maturities as well. Of the brown varieties, industry standard Hybing was again looking the earliest, but had only recorded 25 per cent fallover by 12 August. It produces a good enough yield on harvest, but yields out of storage tend to be below average, Napier reports.
Hybing was closely followed in maturity by Hybound, which came in more mid season last year. It turned in a decent marketable yield on both sites last year, but is average for storage performance. "Being only in its second year of full assessment, it's still early days," says Napier.
Last year, Attraction, Vision and Wellington (all from Syngenta) were ready to lift within a couple of days of each other - and all three do very well in store. More than 36 per cent of Wellington's bulbs in ambient storage were still sound by the May assessment and 71 per cent were recorded as sound three weeks out of a commercial controlled-environment store, the highest in the trial on both counts. "Wellington tends to be average for yield overall, but makes up for it with its storage performance," says Napier.
Vision's ambient storage results, while high at almost 32 per cent by May, were not as good as last year's. "This may be because it was sitting in damp soil when fully mature," Napier suggests. "It was wet from September onwards, so we were unable to get the earlier varieties out of the ground."
Also in the early to mid-season slot, Hytech turned in an average yield overall last year, but did particularly well on the Essex demonstration site. Centro, which has a similar maturity, may not have topped the yield charts at Raker's last year, as it has in the past, but is a consistent performer, says Nickerson-Zwaan range manager John De Soyza.
"It is helped by its early vigour and broad-leaved top," he adds. "The wet September last year was a really good test for its storage ability. In growers' hot box tests (to check for the presence of latent rots) it was coming out as one of the best varieties."
Motion, in its second full assessment year, came in at the same time as its older Syngenta stablemate Sunskin last year. But while it produces average yields, its storage potential is up with the best.
In the preliminaries last year, Hytide and NIZ 37-84 had a timing similar to Arthur and Hylander. With a yield equivalent averaging 78 tonnes per hectare, Hytide was one of the heaviest croppers, and while NIZ 37-84 averaged 74 tonnes it gave one of the highest yields on the Essex site. But for both so far, storage performance looks to be below average. De Soyza describes NIZ 37-84 and NIZ 37-83, in its first trials year, as later-maturing Centro types with similarly vigorous tops. NIZ 37-83 also makes a particularly firm bulb and promises strong tolerance to sprouting.
The last to lift in the 2010 trial was Santero, Nickerson's mildew-resistant variety. With an average yield equivalent to 62 tonnes/ha last year, it was not a high yielder, but it did store well. "It is becoming popular among organic growers because they have got used to getting the best out of it," says Napier.
Of the eight brown varieties in the preliminary trials, Silverado from Advanta looked the earliest, with 20 per cent fallover by 12 August.
ONL353 from Syngenta, which will be named Medallion, has a maturity similar to Napoleon and features very healthy, dark foliage, says crop specialist Nigel Kingston. ONL346, meanwhile, is closer to Sunskin in maturity. "It makes a good root system and has a thin neck," he adds.
Of the two Seminis varieties in the preliminaries, the company is looking to run its own commercial trials of RX 1481, an early variety, next year. "From our own results, it looks very good on long-term storage, even last year when it was a difficult season," says product sales specialist John Hutton. RX 0835 is a few days later and keeps slightly darker foliage. "It's a nice-looking onion with uniform size and signs of having even better storage potential than RX 1481," he adds.
Since 301/5 was first assessed in NIAB trials, it has been reselected by its breeder, Allium Farms, and given the name Red Planet. In previous years it has shown similar late mid-season maturity to Redspark, but this year was looking well ahead at the Raker demonstration site.
Redspark reliably returns a heavy yield - its 65 tonnes/ha average was the highest of the reds last year - and is a good storer too, with 27 per cent of bulbs out of ambient storage still sound by May. The early to mid-season Red Tide produced a similar yield to Red Baron last year and looks to have a similar storage performance. Along with Grenada, it was a week ahead of the field for maturity.
Retano, seen for the first time last year, is in its first year of full assessment. It has late mid-season maturity and gave a particularly good yield on the Essex site last year, although storage performance was slightly behind Red Baron's. "It has a round shape, good sprouting tolerance for a red hybrid and a deep attractive colour," says De Soyza.
In the preliminary trials were Red Light, which was looking early, and, for a further year, Garnet. Garnet has a yield, colour and maturity similar to Red Baron, according to the Allium & Brassica Centre, but more single centres.
For the future, Napier is hopeful that red varieties with inbred mildew resistance are on the way. "Anecdotally, red varieties are more susceptible to the disease," he says. "And because they have tended to be later maturing, if the disease is already established in sets or the drilled brown crop, it can move into red onions fast."
The NIAB trial is funded by the Horticultural Development Company and seed companies. Harvested bulbs from the variety trial can be viewed at the NIAB on 8 November.