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Improving the effeciency of PC in winter through the use of low energy light intensity, long day lighting - HH3603SPC


This project addresses the DEFRA policy objective to develop horticultural production systems that use natural resources efficiently and consistently with the principles of sustainable development (HH36: Sustainable use of natural resources and labour). In particular, the project seeks to evaluate the use of low-intensity, long-day lighting as a potential new means of reducing energy use in UK horticulture by increasing the efficiency with which greenhouse crops convert energy-expensive inputs, heat and supplementary light, into fresh and dry weight. If successful, this low-cost technology will provide a ready means of increasing the outputs, quality and sustainability of a wide range of glasshouse crops, with negligible increases in inputs. By enabling plants to maximise their growth potential, the energy used per unit of production ought to be greatly reduced, enabling production systems to be devised that use natural resources in a more sustainable way.

Although the effects of daylength on flowering have been extensively researched with many commercial benefits, there has been very little research concerning effects of daylength on vegetative growth or on crop yields. However, recent work at Wellesbourne has shown that the use of day extension or night-break lighting is often associated with marked increases in plant dry weight, comparable to those given by the use of high irradiance supplementary lighting. Sporadic reports have appeared in the scientific literature; growing young tomato plants in long days, for example, has been shown to result in an almost doubling of dry weight. The underlying physiology of this response is not known, although the responses may be related to changes in leaf growth and / or leaf chlorophyll content. The responses cannot be explained through increased light integral because the increased daylength is applied using low intensity lighting. Much of the work in the past has been carried out in controlled environment chambers and so we aim to assess whether similar benefits might be obtained for tomato and bedding plant crops through the use of long-day lighting under commercial glasshouse conditions. We aim to involve key industry leaders at all stages of our research to ensure full industry commitment to a follow-on, commercial implementation phase, should our evaluation studies justify this.


Overall aim - to quantify the effects of extending the photoperiod on plant growth and energy requirements for bedding plants and tomatoes. The specific objectives are:

1. To carry out an interpretative literature review on the effects of photoperiod on plant growth and to submit for publication in an appropriate scientific journal.

2. To determine the effects of different fixed photoperiods and night-break lighting treatments on the growth of impatiens, petunias and young tomato plants, and to compare the magnitude of these responses to the effects of light integral.

3. To quantify the benefits of extending natural (changing) daylengths on the yield and growth of semi-commercial tomato and bedding plant crops.

4. To publicise the work through appropriate publications and presentations, and to liaise closely with key industry leaders at all stages to ensure full industry commitment to a follow-on, commercial implementation phase, possibly via LINK if the findings justify this.

Project Documents
• Final Report : Improving the effeciency of PC in winter through the use of low energy light intensity, long day lighting   (1913k)
Time-Scale and Cost
From: 2003

To: 2003

Cost: £98,937
Contractor / Funded Organisations
Horticulture Research International
Natural Resources and Labour              
Organic Farming              
Protected Cropping              
Fields of Study