NIAB Sweetcorn trials - Cobs in the spotlight

As the search for new early sweetcorn varieties continues, Sue Jupe reports on the latest demonstration.

PVSL 7713 has a sweet taste and with its straight kernals the Pro Veg Seeds' newcomer is a contender to the ACX 6800 standard - image: Sue Jupe
PVSL 7713 has a sweet taste and with its straight kernals the Pro Veg Seeds' newcomer is a contender to the ACX 6800 standard - image: Sue Jupe

Poor light levels and below average July and August temperatures delayed the National Institute of Agricultural Botany's (NIAB) sweetcorn demonstration by two weeks. The event, held at the NIAB's Cambridge headquarters, was funded by seven seed companies and featured 25 varieties.

A demonstration rather than a trial, the majority of single unreplicated plots were sown on 16 May, with a few hand-sown later due to seed arriving late. "As of last year, the ten-year average for first pick was 31 August - this year it was delayed to 9 September," says NIAB vegetable specialist Bruce Napier. "The dry May and June didn't help, and then below-average temperatures and sunshine in July, August and September have meant plots have struggled. We recently had near gale-force winds of 40mph, with gusts of up to 107mph."

Evident in the lodging in some plots, Napier points out the degree of crop leaning did not correlate with height/maturity. "Some varieties have better standing ability, probably due to stronger roots," he says. "This year we scored varieties' plots from one to nine according to leaning, with 'nine' being upright." In his view the year has been a stern test for growers - the only saving grace was reduced demand so growers have not had to source supplies from elsewhere.

Search for early varieties

Sown in April under plastic, the first UK crop is generally harvested in the second to third week of July. "In Cambridgeshire the crop is slightly later," Pro Veg's Roy Bingham explains. "It used to be the northern extreme of sweetcorn growing in the country, but it's now grown in Yorkshire. The crop generally grows best in sheltered areas on the south coast, Suffolk, Essex and the Thames Basin. In France and Germany it is so much easier."

Breeders are still looking for an elusive new early variety to challenge the Abbott & Cobb standard ACX 6800, which is proving hard to beat. Taking just 94 days to mature in 2010, this year ACX 6800 took slightly longer at the NIAB site - 116 days. But it performed well, producing well-filled cobs weighing 218g with 18.5cm of grain, a few white bracts, no tillering and scoring five for leaning.

Among seed supplier Abbot & Cobb's new material, ACX 7501 is well-suited to UK weather and looking the most likely contender, according the firm's Tony Perryman. Napier says it produced nice-looking, well-filled cobs, weighing 226g and with 20.5cm of grain. The plants are above average-height, held up well to the wind and scored seven for leaning.

Meanwhile, Bingham hopes Pro Veg entrant PVSL 7713 will compete with ACX 6800. "Producing good straight rows of kernels, it has a great taste - half way between Xtra-Tender and normal," he says. "We're yet to see how early it is but it probably falls in the second early slot. There is always demand for new earlies to kick-off the UK season."

Taking 121 days to mature in Cambridgeshire this year, PVSL 7713 produced well-filled cobs weighing 172g with 20cm of grain and minor bracts. Napier describes it as tough to pick but easier to peel. While most varieties taste good, Bingham says they differ in texture. "Xtra-Tender has a wonderful soft texture but are more difficult to grow and harvest. Supermarkets are not 100 per cent sold on them. They deserve a special label to differentiate them."

Nickerson's tall newcomer, super-sweet variety Kuatour, matured in 119 days and stood up well scoring seven for leaning. According to Napier, it produced well-filled cobs weighing 217g of more than 20cm in length.

Recent introductions

Commercial variety Signet, a recent introduction from Seminis, proved the earliest to mature, taking 109 days. "Unlike the American market, where 90 per cent are sold loose with the husk on, the UK market is dominated by two-to-four cobs in a pack, making it easier to get skin damage," explains technical development specialist Casper Jonsen.

"Signet has a slightly thicker pericarp, better suited to mechanical harvesting. Producing a nice cylindrical cob, it has good tip fill, but this is not a must because cobs here are generally trimmed. Early varieties are sought after because supermarkets are keen to establish UK produce and it helps growers deliver consistently and get established."

A good yielder, this year Signet produced cobs weighing 181g with 19cm of grain and did not throw any tillers. However, it suffered severe leaning, scoring only three.

Tozer sponsored five plots including XTH 1975, a pre-commercial Xtra-Tender super-sweet variety. Among the four mid/mid to late season varieties, TZC GO stood out as particularly promising with its darkish-yellow cob demonstrating good tip fill.

Unlike several others, TZC GO produced no tillers and remained relatively upright, scoring eight for leaning. "With the UK industry moving increasingly toward mechanical harvesting, lodging is important," says Tozer's Nick Forsyth. "If the crop lodges it has to be hand picked, making it very labour intensive.

"It's been a difficult season. The hot start brought the crop on but the past few weeks have been very difficult as everything has slowed up. Each season is different and brings its own problems."

Perryman agrees it has been a unique season. "The crop is noticeably shorter, due to lack of moisture at critical times." Although he hopes to be proved wrong, he predicts a likely reduction in sweetcorn production next year. "The margins are always close. Growers can't afford to carry crops - all specialist crops need to make money. Everyone has taken a hit on the weather this year."

US markets versus UK markets

In the USA, sweetcorn is grown in many regions with bi-colour varieties dominating. According to Abbott & Cobb's Chris Roberts, in Illinois the market took 15 years to switch from traditional yellow cobs.

"The UK market still favours yellow. We have tried to introduce variants but to no avail," he says. "Generally the younger UK generation prefer Xtra-Tender varieties, while older generations prefer more corn flavoured, not so sweet, varieties - with the latter dictating the market. Taking into account economic conditions, the UK market is not looking to diversify and change. Opportunities for bi-colours and white sweetcorn are in the catering sector."

Breeding for the UK market, Abbott & Cobb is pursuing varieties suitable for mechanical harvesting and targeting the tray pack and convenience market. "Dark-yellow kernel colour is key," says Roberts.

In the USA, the majority is sold loose at the roadside, with buyers checking on tip fill.

Supermarkets generally specify minimum 18-20cm length, 4.6-5cm width, at least 16 rows of kernels and perfect conformation. "In some varieties the rows are very jumbled," says Reg Bingham of Pro Veg.

"Supermarkets like uniformity. Earliness is also very important. In the UK, we are on the extremes of growing latitude and temperature."

Weather and light levels compromise crops

Poor light levels and low temperatures in July and August are creating major setbacks for this year's crop. As many crops struggle to finish, some believe that flavour has been compromised by reduced sugar production.

"August sunshine levels were 25 per cent down on the average, while temperatures were one degree below," says Tony Perryman from seed supplier Abbott & Cobb. "The season started well. Growers were able to plant when they wanted to but unusual weather has interfered with maturity and some crops are not likely to finish at all."

Being totally reliant on sunshine and heat, this year has been a disaster for sweetcorn, he says. "In Worcestershire, rainfall is 4.5 inches below average. Many growers have resorted to a lot of irrigation, bumping up costs and eating into already slim margins, effectively taking the profit out of the crop."

Growers' problems have been compounded by recent wind and rain damage. "The real problem comes when you get both together as the crop lodges," Perryman explains. "It is disappointing because early on the crop looked fantastic."

He believes that the abnormal weather has had an impact on flavour as well as dampening demand. "August wasn't a barbecue month," he says. "Sweetcorn is associated with al fresco eating."

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