Design considerations and operational management of greenhouse for tomato production in semi-arid region

An overview of the design considerations and the operational characteristics for production of tomato in a greenhouse in a semi-arid region is provided. The integration of the automation, culture and environment requires an understanding of the production needs of the crop, and the specialized weather conditions of the Arizona climate. The demand on the plant imposed by the greenhouse climate, including air temperature and humidity, or atmospheric vapor pressure deficit (VPD), leaf temperature, and solar radiation must be balanced with the water availability within the plant root zone, as affected by the electrical conductivity of the nutrient solution and the irrigation frequency. The crop production system requires that nutrient delivery be automated to provide a consistent availability of nutrient formulation and concentration in proportion to the general daily fluctuating water demand. An automatic means to determine water demand that will vary the irrigation frequency and the nutrient concentration is important to provide the desired stress for crop production. The climate control includes monitoring and feedback mechanisms to firstly, minimize the potentially harsh diurnal fluctuating desert conditions of low air humidity, high solar radiation, and water quality with high salts, and then, to secondly, alter the plant microclimate to match the stage of plant growth and its production condition. The greenhouse structure should be of sufficient height for buffer volume needed to offset the large daily environmental fluctuations. The structure system must also offer air exchange capacity, shading, and evaporative cooling to help maintain the desired air temperature and relative humidity for crop production. Experiences and research studies within each of these areas of production system, climate control and greenhouse structure will be presented, including: production of greenhouse tomatoes within a high-wire, continuous production system; modulating plant vegetative or reproductive tendency with a combination of root zone and aerial microclimates; improving fruit market quality; and greenhouse structure design variations for improved cooling and reduced water utilization.