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The general objective of this activity is to develop an organic greenhouse production system for intercrop tomato and extended sweet pepper crop under supplemental lighting (SL) providing . Specifically:

1. Design an organic growing system that will optimize light penetration through the canopy and allow soil-grown intercropping plants (intercrop tomato)
2. Improve the SL distribution within the canopy and light use efficiency by using a combination of light emitting diode (LED) and high pressure sodium (HPS) lamps
3. Characterize nutrient requirements and soil biological activity according to nonstop growing crops under SL
4. Optimize the irrigation and fertilization management according to SL
5. Evaluate the light use efficiency and energy use efficiency of the proposed growing systems
6. Evaluate the effect of SL and intercrop on fruit quality

Demand for organic food in Canada has increased by 15 to 25% annually with fresh vegetables representing 25% of all organic food sales. Even though there is a large demand, Canada still imports 75 to 85% of their organic products, mainly from the United States. This increasing demand by Canadian consumers is mainly due to health concerns over pesticide residues on foods and environmental concerns. To fulfil part of this demand, sustainable organic production of fresh vegetables grown locally has to be developed and proposed to the Canadian horticulture industry. The development of an organic greenhouse production system using supplemental lighting (SL) is a promising alternative to satisfy consumer needs, and could also contribute to the Canadian greenhouse industry growth and long term durability.

The greenhouse industry is an important segment of the Canadian agri-food industry (estimated value: $2.5 billion in 2007), with more than $1.2 billion for vegetable crops. However, only 3.0% of the Canadian greenhouse vegetables are grown using SL, while 3.3% are grown organically without any SL. In Finland, 35% of greenhouse vegetables are grown under SL and more than 200 ha of vegetables are under SL in The Netherlands, providing local and high quality products on a year-round basis. During the last 20 years, it has been clearly shown that SL under low light natural conditions, such as those in Canada, increased greenhouse vegetable yield of high quality and allowed year-round production of locally grown products.

Moreover, the use of high pressure sodium (HPS) lamps may contribute up to 25-40% of the heating requirement in Canada, which represents in average a production cost of around 30%.  Recently, the effects of various light sources and spectra on vegetable crop responses have been examined. Results indicated that light quality and distribution pattern during the day may improve the productivity of greenhouse vegetables, and constitute a powerful tool to initiate specific physiological responses that improve energy use efficiency (EUE). Moreover, interlighting, in combination or not, to above-canopy SL and intercrops could contribute to a more effective use of light since inside canopy light levels are low.

Consequently, the general objective of this activity is to develop an organic greenhouse production system for intercrop tomato and extended sweet pepper under SL providing year-round locally-grown fruits. More specifically, this project aims to:

1. Design an organic growing system that will optimize light penetration through the canopy and allow soil-grown intercropping plants
2. Determine the optimal SL level and composition for an organic intercrop tomato and a sweet pepper extended crop where overall canopy productivity and fruit quality will be optimized
3. Characterize nutrient requirements, soil biological activity and pest biological control according to nonstop growing crops under SL
4. Optimize the irrigation and fertilization management according to SL
5. Optimize the plant fruit load according to SL
6. Evaluate the heat contribution provided by the SL and the crop effect of cold light
7. Evaluate the light use efficiency (LUE) and energy use efficiency (EUE) of the proposed growing systems
8. Evaluate the effect of SL and intercrop on fruit quality.

To meet these objectives, three sets of experiments (split plot design with 2 or 3 replicates) will be conducted at commercial (intercrop tomato; Sagami Inc.) and experimental sites (growth chambers and greenhouse of Université Laval; tomato and sweet pepper) on conventional and organic growing systems. Conventional systems will be used to establish a baseline for the productivity that can be reached with an organic crop under SL when nutrient availability can be a limiting factor. Conventional plants will be grown in raised bed containers filled with coco fibers and irrigated with a conventional nutrient solution. Organic plants will be grown in soil amended with organic matter and fertilized with solid certified amendments. LED light arrays and lighting regimes for tomato and sweet pepper will be studied at Université Laval and validated on a commercial scale in years 2 and 3. At the commercial level, two row spacings for an intercrop tomato system will be compared during the first year in four greenhouse bays under HPS SL. Plants will be intercropped after 6 months and raised on wires in a V-shaped manner. During years 2 and 3, LED systems will be placed into the canopy (interlighting) in order to deliver 50 µmol m^-2s^-1 (tomato) or placed at the top in complement to HPS lamps (sweet pepper). For each lighting regime, optimal plant fruit load under SL will be determined. The combined effect of PPFD and different wavelengths on morphology, growth, mineral nutrition, productivity and quality of tomato and sweet pepper will be evaluated together with the control of pathogens and insects. These experiments will ensure immediate technology transfer and will adapt our sustainable organic growing system to real life. Results from this project will increase the profitability and competitiveness of Canadian enterprises by increasing yield and quality of locally-grown products, and will reduce risks associated with organic greenhouse production by developing new growing systems with a year-round production.

• [PDF - 3.6 MB]
  • The Canadian Organic Grower. 2012
• Organically-grown greenhouse tomato under supplemental lighting – optimization of the light distribution
  • Plant Canada Conference. 2011
• [PDF - 51 kB]
  • Canadian Organic Science Conference. 2012
    
• [PDF - 51 kB]
  • Canadian Organic Science Conference. 2012

• • Acta Horticulturae (2007) 744: 279-294
• • HortScience (2009) 44: 800-809