A viable greenhouse technology

The AUD$3 million Young Sang & Co retractable roof greenhouse recently opened in Bundaberg, Australia, represents the future of greenhouse technology in warm, arid and semi-arid regions exposed to the vagaries of extreme weather events. The Bundaberg region is particularly known for its violent storms, which became a reality on the eve of the official opening of the new greenhouse. The timing could not have been better for the Canadian greenhouse designer, Cravo; the structure withstanding the fierce hail storm and 100kph winds, an exemplary testimony to the benefits of this technology. Retractable roof greenhouses are suitable for soilless and ground growing systems, without the added expense of ancillary equipment to control temperature and humidity, which is essential in a closed greenhouse environment.

Retractable roof greenhouses have been commercially available since the early 1990s. Since then, they have been found to help prevent many of the problems associated with field and nursery grown plants by protecting leaves and roots from environmental extremes such as excessive or insufficient cold, heat, rain, hail or wind, and by preventing disorders associated with insufficient transpiration and the resultant lack of water stress typical in conventional greenhouse environments. This is possible because retractable roof greenhouses can create an outdoor, greenhouse and modified greenhouse environment simply by positioning the roof, walls and curtain systems, depending on the design and outdoor weather conditions. Plant responses in retractable roof greenhouses include stronger root systems, reduced internode lengths, thicker cuticles, fewer root and foliar diseases, fewer insect pests, and less stress and shock following transplanting. Also, chemical fungicides, growth regulators and pesticide applications have been reduced significantly. Growers of outdoor crops have found benefits including up to a 50% reduction in crop production cycles, and about a 50% reduction in summer water usage. Retractable roof greenhouses have caused crop management strategies to be rewritten, as well as guidelines for how greenhouses are built and where they are built (R. Vollebregt, 2004, ActaHortic. 633.4).

With Australian grower confidence down in the last quarter of 2015 as a result of rising production costs and shrinking profit margins, retractable roof greenhouses are a viable protected cropping technology with production cost savings, at the same time improving product quality and yields in warm, arid and semi-arid regions. The technology is a step away from Dutch greenhouse technology that dominates grower thinking across all climates, but is less efficient in warm countries without costly climate control equipment.

As we come to the end of another year, I would like to take this opportunity on behalf of the Practical Hydroponics & Greenhouses team to wish our readers worldwide a happy and safe holiday season.The UN General Assembly has declared 2016 the ‘International Year of Pulses’. As defined by the Food and Agriculture Organization (FAO), pulses are annual leguminous crops yielding between one and 12 grains or seeds of variable size, shape and colour within a pod, used for both food and feed. Pulse crops include lentils, beans, peas and chickpeas, which are a vital source of plant-based proteins and amino acids for people. 2016 is also the Year of the Monkey, the ninth of the 12 animals in the Chinese zodiac. Lucky colours are white, blue, gold; lucky numbers are 4 and 9; and the lucky flowers are chrysanthemum and crepe-myrtle.  Ω


PH&G December 2015 / Issue 162