Wageningen University & Research staff claim to have harvested 110kg per square metre of high-wire winter cucumbers in a specially designed cutting-edge glasshouse, consuming just 18cu m of gas in "a super-healthy glasshouse without Botrytis, Mycosphaerella or any other trouble". Researchers Jan Janse and Frank Kempkes presented the findings of the EUR267,000 (£232,000) Dutch government-funded Winter Light Cucumber Growing project to growers last month.
The 18-month project, which concludes at the end of this month, was based at the highly insulating 2SaveEnergy Glasshouse facility in Bleiswijk, in the western Netherlands. Boasting a double-deck consisting of diffuse glass as well as state -of-the-art screening, it employs the "New Cultivation" (Het Nieuwe Telen) approach, using pipes under the gutter to dehumidify the glasshouse with outside air.
Researchers sought to create a crop with a minimal leaf area, so ensuring available assimilates are concentrated on crop formation while minimising loss of energy to unnecessary evaporation. "The glasshouse is optimised so that from October to March at least 10 per cent more light is available to the crop compared to a good reference greenhouse," says Kempkes. "Everything down to the last rod has an enhanced coating that reflects 87 per cent of the incident light. But by far the largest part of the total light gain is due to diffuse glass."
Cucumbers of the Hi-Jack variety were planted on 28 December at a density of 1.67 plants per square metre along 1.8m-wide alleys. Harvesting began on 7 February.
Head of energy policy at the Glasshouse as Energy Source programme Aat Dijkshoorn ascribed the success to "the high light transmittance of the glasshouse, the diffuse light, which was not reflected away even on the most sunny days, the high day temperatures in bright light, the cultivation method according to the basic principles of the New Cultivation and the excellent crop care, which in practice is more difficult to organise at large companies". But he admitted: "There was a healthy scepticism among growers that results in a test greenhouse also can be achieved in practice."
Meanwhile, Bayer's vegetable seed division Nunhems has published a guide on how to embark on and optimise high-wire cucumber growing. "High production is only one of the benefits," it says. "High-wire also delivers extremely high-quality fruits and gives opportunities for market-driven production and automation."
But the guide warns that the technique "requires serious investments and strict labour planning". With growers still gaining and sharing experience with the system, "high-wire is still far away from its limit", it adds.
Bayer expects the proportion of long cucumbers grown on high-wire systems to grow from the current 19 per cent to at least 30 per cent over the coming five years, with growers in northern Europe, Canada and Russia most likely to make the transition. Accordingly, Nunhems has focused on breeding cucumber varieties specifically for high-wire production, such as its open, small-leaved HiRevolution series.
High-wire is also suitable for supplemental lighting, allowing growers to extend the growing season, it adds. "Lighted high-wire cultivation is still in its infancy but developments go very fast. At the moment, mainly high-pressure sodium top lighting is being used. LED top and inter-lighting are being developed and tested at a larger scale. Research on different spectra is showing the first interesting results and may lead to even more benefits in yield, quality and taste."
- The first in a series of grower guides, The Only Way is Up, is available for free at www.nunhems.co.uk.