Dutch glasshouse researchers have achieved savings of 33 per cent in heating and 30 per cent in electricity growing an out-of-season tomato crop using LED interlighting and diffuse glass
The trial is the first to combine the two approaches. The team from Wageningen UR and the Green Q Improvement Centre grew a crop of Komeett tomatoes under three different growing systems in separate glasshouses between August 2012 and March 2013.
The systems included a control regime using only high-pressure sodium (HPS) assimilation lighting, a regime using HPS together with Philips LED interlighting, used to supplement daylight under the "New Lighting" strategy, under diffuse glass; and a regime using the same lighting regime under conventional glass.
Explaining the rationale, project leader Tom Dueck said: "In both cases, more light reaches a greater leaf area, giving you more growth and production."
Dueck added that he was surprised at the net effect of the diffuse glass, expecting it "to have not such a big effect in the winter but rather in the summer".
Wageningen UR crop researcher Jan Janse said: "In the winter months, the diffuse light has a positive effect. Under hybrid lighting, the leaves are stronger than under HPS alone, and the plant growth is generally better."
However, the research report published this month conceded: "Botrytis infection occurred in December and it remained constantly present."
The trial formed part of the Kas als Energiebron (Glass-house as Energy Source) programme that was financed by the Horticultural Production Board along with the Dutch government.
Diffuse glass gains
Diffuse glass is attracting interest in Dutch protected horticulture because it spreads light more evenly around the crop, supplying a greater total leaf area with the energy to grow. It has already yielded what Wageningen UR describes as "significant production increases" in unlit crops.