Energy conservation and light management were hot topics at the Canadian Greenhouse Conference October 4-5 in Niagara Falls, Ontario. Here were some of the highlights for greenhouse vegetable growers.
Energy conservation. Rupp Carriveau, University of Windsor, examined the technical and economic feasibility of a novel Solar Energy System designed to reduce dependency on carbon-based fuels for heating and grid-connected power for electricity.
Leo Marcelis, Wageningen University, The Netherlands, demonstrated how energy can be saved in greenhouses with better understanding of crop physiology. Some techniques include: intensive use of energy screens to conserve heat, controlled inlet and distribution of outside air to regulate air humidity, flexible temperature set points based on energy losses and plant demand.
Marcelis recommends that more focus should be on the microclimate near the plant organs than on the average greenhouse climate. For instance, the temperature of the shoot tip may deviate 4°C from that of the air. Temperature of the shoot tip has large effects on the development of the plant. Leaves are important for plants to intercept light and to photosynthesize. For efficient use of light, plants should initially have high rates of leaf development. However, in fruiting vegetables, the plants have a larger leaf area index than needed. A number of studies have shown that production efficiency can be increased if fewer leaves are formed or can be removed in an early stage. Removing leaves may also lead to less transpiration which can contribute to energy savings during some periods of the year.
Many growers are considering switching to LED lamps, but are faced with substantial investment. A panel presentation summarized the differences between high-pressure sodium (HPS) and Light-Emitting Diode (LEDs). Panel participants included: Marco de Leonardis, Freeman Herbs, Beamsville, Ontario; Lasse Schulze, Peace Naturals, Stayner, Ontario and Ruben Houweling, Houweling Group, British Columbia.
Pollination is affected by artificial lights, as Roselyn Labbe has found in her research at the Agriculture and Agri-Food Canada research station in Harrow, Ontario. Bumblebee activity is directly affected by seasonal changes to light as well as to supplemental lighting. The increasingly common use of HPS and LED lighting has the potential to affect the duration and intensity of daily bee activity.
The strawberry has relatively complex physiology that demands production technologies to be optimized based on cultivars, growing systems and climate conditions. Chieri Kuboto, Ohio State University, talked about high quality transplant production as well as growing systems, light management and substrates that are needed to support this emerging industry.
Bert Meulenbroek, Fresh Forward Breeding, from The Netherlands addressed traits and development of the ideal strawberry plant. Nursery workers need to have knowledge of the physiology of the plant, excellent phytosanitary company regulations/treatments, advanced growing skills and proper facilities and equipment.
In Belgium, Koen Lavrysen has had good success in strawberry production. More than 70 per cent of the strawberries (50,000 tons/year) are grown on substrate in greenhouses or plastic warehouses. He discussed the key parameters: temperature settings. CO2 levels, importance of rH light, use of screens and water management.