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, hydroponic production systems can lead to increased food security. For example, hydroponic and controlled environment agriculture can improve year-round availability of and increase proximity to safe and nutritious produce ( Premanandh, 2011 ). Depending on

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Greenhouses that are well sealed can result in carbon dioxide (CO2) drawdown and suppressed plant growth. While growers can add supplemental CO2, it is unknown how supplemental CO2 fits within the framework of sustainable crop production in greenhouses. In this study, supplemental CO2 was used in combination with reduced temperatures to evaluate the productivity of ‘Grand Rapids’ lettuce (Latuca sativa) compared with a traditionally maintained, warmer, and well-insulated greenhouse without supplemental CO2 at a commercial facility. Simulations using Virtual Grower software based on identical greenhouses compared fuel use and carbon (C) consumed because of heating and CO2 supplementation. Models were verified with measurements in a well-sealed commercial greenhouse; CO2 quickly decreased to below 300 ppm in a nonsupplemented greenhouse containing plants. Supplemental CO2 boosted total leaf number and mass of lettuce even though temperatures were maintained 3 °F lower in elevated CO2 than in the traditional management scenario. Maintaining a cooler greenhouse but adding CO2 decreased total carbon (C) consumed (by combined fuel use and CO2 supplementation) by 7% during the 3-month season that required a well-sealed greenhouse. Additionally, fuel savings because of lower temperature set points paid for the cost of adding CO2. The use of CO2 enrichment should be considered as a tool in sustainable systems when its use can counteract the plant growth and development reductions brought on by lowered temperatures.

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Using greenhouse tomato (Solanum lycopersicum) as a model system to produce pharmaceutical proteins, electrical conductivity (EC) of hydroponic nutrient solution was examined as a possible factor that affects the protein concentration in fruit. Transgenic tomato plants, expressing F1-V protein, a plant-made candidate subunit vaccine against plague (Yersinia pestis), were grown hydroponically at high (5.4 dS·m−1) or conventional EC [2.7 dS·m−1 (control)] with a high-wire system in a temperature-controlled greenhouse. There was no significant difference in plant growth and development including final shoot dry weight (DW), leaf area, stem elongation rate, or leaf development rate between high EC and control. Net photosynthetic rate, transpiration rate, and stomatal conductance (g S) of leaves were also not significantly different between EC treatments. For both EC treatments, immature green fruit accumulated DW at a similar rate, but dynamics observed in fruit total soluble protein (TSP) and F1-V during the fruit growth were different between the two ECs. Fruit TSP concentration per unit DW decreased while TSP content per whole fruit increased as fruit grew, regardless of EC. However, TSPs were significantly lower in high EC than in control. Fruit F1-V concentration per unit DW and F1-V content per whole fruit were also lower in high EC than in control. Our results found that increasing EC of nutrient solution decreased TSP including the vaccine protein in fruit, suggesting that adjusting nutrient solution EC at an appropriate level is necessary to avoid salinity stress in this transgenic tomato.

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fumigation due to the added expense, management, and negative impact on the environment. Most farms are monitoring and improving soils and using crop rotation as alternatives to soil fumigation. Interest in controlled-environment agriculture (CEA) of

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High tunnels are becoming an increasingly important production tool for vegetable, small fruit, and cut flower growers in many parts of the United States. They provide a protected environment relative to the open field, allowing for earlier or later production of many crops, and they typically improve yield and quality as well as disease and pest management. Producers, ranging from small-scale market gardens to larger scale farms, are using high tunnels of various forms to produce for early markets, schedule production through extended seasons, grow specialty crops that require some environmental modification, and capture premium prices. The rapid ongoing adoption of high tunnels has resulted in numerous grower innovations and increased university research and extension programming to serve grower needs. An informal survey of extension specialists was conducted in 2007 to estimate numbers (area) of high tunnels and crops being grown in them by state, and to identify current research and extension efforts. Results of this survey provide an indication of the increasing importance of these structures for horticultural crop production across the country.

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Agricultural Experiment Station paper D-03130-07-96, supported by State funds and CCEA, the Center of Controlled Environment Agriculture, and NJ-NSCORT. Reference to commercial products implies no endorsement, nor discrimination of other products.

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The diversity of coverings for the greenhouse and other plant production structures has increased dramatically during the past 4 decades. This has resulted from the availability of new types of covering materials and enhancements of previously existing materials, as well as the demands for technological improvements within the expanding controlled environment agricultural industry. The types of coverings currently available are dominated by plastics. These range from traditional glass to the recent advent of polymer plastics, such as thin films or multilayer rigid thermoset plastic panels. Available enhancements such as ultraviolet radiation (UV) degradation inhibitors, infrared radiation (IR) absorbency, and anti-condensation drip surfaces, as well as their physical and spectral properties are discussed. The selection of specific covering alternatives has implications for the greenhouse superstructure and its enclosed crop production system.

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Sweetpotatoes (Ipomoea batatas) are nutritious, easily stored, and well adapted to a variety of organic farming operations. This widely consumed root crop is propagated through the use of cuttings, known as slips. Slips are commercially grown primarily in the southeastern United States, and growers in the central United States still have limited access to sweetpotato planting material. Production of organic slips in high tunnels (HTs) could be a profitable enterprise for growers in the central United States given the season extension afforded by controlled-environment agriculture, which could allow growers to diversify their operations and facilitate crop rotation. In trials conducted in 2016 and 2017 at two research stations in northeast and south central Kansas, a systems comparison was used to evaluate the yield and performance of organic sweetpotato slips grown in HT as compared with the open field (OF), with four to six replications at each location. Propagation beds planted with ‘Beauregard’ seed roots in 2016 and ‘Orleans’ in 2017 were established in HT and OF under similar cultural methods and planting schedules. Slips were harvested from both treatment groups and transplanted to field plots to investigate the impact of production system on transplant establishment and storage root production. Slip yield from HT was greater than OF at both locations in 2016 (P ≤ 0.001), but this trend was inconsistent in 2017. Slips grown in HT were on average 12% less compact (slip dry weight per centimeter length) with fewer nodes than their OF counterparts in 2016. Nonetheless, mean comparisons for vine length, stem diameter, and total marketable storage root yield were not significant between HT and OF treatments (1.7 and 2.1 lb/plant, respectively). Similarly, the number of marketable storage roots for HT and OF groups was comparable (3.4 and 3.8 storage roots/plant, respectively). Although more research is needed to evaluate the feasibility of slips grown in HT and to determine recommendations for seed root planting densities, results from this study suggest that HT organic sweetpotato slip production could be a viable alternative to OF production as it relates to slip performance. According to this study, HT production could be a useful mechanism for growing sweetpotato slips, which could provide regional growers more control over planting material. Furthermore, HT slip production could promote the adoption of an underused vegetable crop that can be grown throughout many parts of the United States.

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regulators. Evans et al. (2006) developed 15 virtual field trips that demonstrate various technologies and management strategies used in greenhouse management and controlled environment agriculture. Although these educational advancements are innovative and

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