Abstract. Many methods of protected agriculture are used to modify the growing environment of plants. Ideally, plant production would take place in regions that do not require protective structures, regions that present ideal temperatures, no harsh extremes, and sufficient but not excess precipitation. This is not the case however, as most countries, save for a select few, require various forms of controlled environment agriculture to protect crops against climatic and environmental extremes. Although the greenhouse industry has developed vast amounts of technology for the temperate climate regions of our planet, much remains to be improved in terms of protected agriculture in the more extreme climates. Tropical, arid, polar and urban locations offer contrasting environments that present various challenges for plant growth. Some challenges are specific to each location, while others are common across them. Tropical and arid climates offer high solar radiation, but present harsh temperature and relative humidity conditions. Most protected agriculture structures are relatively open in nature to ventilate and discharge heat, but are susceptible to pests and diseases. On the other hand, polar climates and urban environments often lack solar radiation and require a high level of control of the air quality. The structures used in these environments are relatively enclosed to entrap heat (polar) and to make efficient use of space. The sustainability of available technologies and energy efficiency are important themes present in all discussed climates and environments. Protected agriculture technologies offer solutions to growers in locations with extreme climates wishing to produce high yields of high quality crop, and this article presents a review of the existing challenges and of the advancements made in this field. Keywords: Arid climate greenhouse, Evaporative cooling, Natural ventilation, Protected agriculture, Tropical climate greenhouse, Urban agriculture, Vertical farming.

There has been increasing pressure on farmers in Europe to reduce the emissions of ammonia from their land. Due to the current financial climate in which farmers have to operate, it is important to identify ammonia control measures that can be adopted with minimum cost. The planting of trees around farmland and buildings has been identified as a potentially effective and low-cost measure to enhance ammonia recapture at a farm level and reduce long-range atmospheric transport. This work assesses experimentally what fraction of ammonia farm woodlands could potentially remove from the atmosphere. We constructed an experimental facility in southern Scotland to simulate a woodland shelterbelt planted in proximity to a small poultry unit. By measuring horizontal and vertical ammonia concentration profiles within the woodland, and comparing this to the concentration of an inert tracer (SF6) we estimate the depletion of ammonia due to dry deposition to the woodland canopy. Together with measurements of mean ammonia concentrations and throughfall fluxes of nitrogen, this information is used to provide a first estimate of the fraction of emitted ammonia that is recaptured by the woodland canopy. Analysis of these data give a lower limit of recapture of emitted ammonia, at the experimental facility, of 3%. By careful design of shelterbelt woodlands this figure could be significantly higher.

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During the North American crop-growing season, although daytime temperatures may remain well above freezing point, nighttime temperatures can easily drop below 0 °C for a few hours. The effects of frost are felt in small operations, such as residential gardens, or in specific areas of a larger operation. Various large-scale measures exist for crop frost protection but they are neither portable nor flexible. A fully automated portable frost-protection misting system that makes use of the latent heat of fusion of water was developed and tested on tomato (Solanum lycopersicum) and sweet orange (Citrus sinensis) at the Macdonald Campus of McGill University (Saint-Anne-de-Bellevue, QC, Canada). The water tank stores up to 20 gal of pressurized water and detachable auxiliary air tanks provide additional line pressure. The device is lightweight, portable and provides flexible, overhead water misting for two 25-ft rows of crops. It activates autonomously using a thermostat, battery pack, and solenoid valve, and the outlet pressure is regulated using a pressure regulator. It is easily installed and dismantled for expedient relocation and the dynamic system of tubing and nozzles can be modified as required. The system was tested in subzero ambient air temperature ranging from −7.1 to 0 °C. During misting, the flesh of the targeted tomato fruit remained, on average, 3.1 and 3.6 °C warmer than ambient temperatures. The use of the system is currently limited by the infrequent formation of ice on the misting nozzles and in the water lines due drastic drops in temperature.