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Operational cost of producing lettuce (Lactuca sativa) during the winter in greenhouses is high in the northern regions of the United States due to the addition of supplemental lighting (SL) and heating. Crop productivity in greenhouses should increase to offset high operational costs and maintain profits. Factors including SL composition, heating efficiency, suitability of production systems (PS), and cultivar performance can affect crop productivity. Research-based information on optimizing the above environmental- and production-related factors is limited. This information is critical for growers to make informed decisions and increase profits during winter hydroponic production. We evaluated the interactive effects of SL composition, solution temperature, PS, and cultivar treatments on lettuce shoot dry weight (SDW, g·m−2) and shoot water content (SWC, %) in a greenhouse maintained at suboptimal air temperature (13.7 °C) using a split-plot design. There were three light treatments (sunlight without SL, sunlight + narrow-spectrum SL at nighttime, and sunlight + full-spectrum SL at nighttime), two solution temperature levels [heated (18.8 °C) and unheated (13.2 °C)], two hydroponic PS [constant flood technique (CFT) and nutrient film technique (NFT)], and eight cultivars included in the study. Results indicated that 1) a narrow-spectrum SL at nighttime in combination with heated solution resulted in maximum SDW of lettuce, 2) the SDW and SWC (major determinant of economic yield) increase between the heated and unheated solution temperature treatments was higher in the CFT than in the NFT, and 3) the positive effects of using heated solution were seen mainly in the green-color cultivars. Our research identified the optimal spectral composition of nighttime SL, tested the positive effects of alternate heating methods using heated solution on plant growth under suboptimal air temperature conditions, compared the suitability of two hydroponic PS for lettuce production, and quantified yield potential of several lettuce cultivars in hydroponic production during winter. Growers can use our research findings to make informed decisions about their investment and to maximize hydroponic lettuce productivity and profits during winter.

There is a growing demand for farm management systems that can track plant growth, allow automatic control and aid in real-time decision making to make indoor farms more viable. IoT is being applied to meet these needs and numerous researchers have created prototypes for specific purposes with sensors, algorithms, and automations. There is, however, a critical need for comprehensive large-scale experiments to test the aspects of such systems' availability, scalability, reliability, especially the low-cost ones. The purpose of this paper is to develop a low-cost IoT ecosystem using off-the-shelf components in an indoor farm setting to move from a prototype to a real-world testbed for experiments and address some of the challenges identified. This testbed realized collection and monitoring of nutrient solution, light intensity, environmental variables, images, and corresponding actuation of LED, irrigation, camera modules using commercially available sensors, components and Raspberry Pis, Arduino microcontrollers for computing. It featured a cloud-based dashboard for remote monitoring and control. The developed testbed is used to successfully investigate the effects of nutrition, lighting, and density on growth of microgreens guided by a statistical design and can motivate, serve as a reference to interested growers. This study complements and expands the previous works on building low-cost IoT farm systems. While the experience with the testbed indicates its importance in conducting research in a practical setting, it also points to some major lessons from the field which are described in detail in the paper.

As several sub-Saharan African countries are entering into the commercial production of geranium essential oils, this work sought to characterize the oil quality of Pelargonium sp. based on organoleptic, physicochemical and chemical properties from different Southern and East African countries to highlight the importance of germplasm selection in the commercial production of oils and to develop base-line yield information. In 2002, Rwanda began to rebuild their essential oil industry, and locally available Pelargonium cultivars were introduced into cultivation trials. The organoleptic evaluation and chemical profile (citronellol 13%, linalool 18% and geraniol 35%) showed that these oils were not suitable for international markets, but may have an important role in domestic markets. In an effort to upgrade the essential oil industry to higher standards, new geranium plantlets of the Bourbon type were obtained from South Africa and distributed to several sites in Southern and Eastern Africa. The newly introduced cultivar yielded essential oils with a suitable organoleptic and chemical profile (citronellol 31%, linalool 3% and geraniol 7%). In Zambia, a commercial grower was also producing geranium oils that were later deemed not suitable for international markets. While in Madagascar, a country with a long history of producing geranium in small land units by many small-scale commercial farmers, those samples analyzed in this study were found to produce high quality oil similar to the Bourbon type. These results clearly demonstrate that the selection and introduction of a specific strain or chemotype with the acceptable organoleptic and chemical profiles are among the key factors needed to obtain high quality essential oils that will meet international expectations and standards, prerequisites for the successful establishment and sustainability of an essential oil targeted for the global trade.