Domestic production of ginger (Zingiber officinale) in the United States is limited by the availability of quality planting material and seasonal constraints, except in southeastern regions. Protected cultivation can extend the growing season, and identifying suitable soilless substrates and optimal fertigation rates are essential for efficient containerized production. Therefore, the objective of this study was to evaluate the growth and rhizome yield of ginger using different soilless substrates and fertigation rates under greenhouse conditions. Two separate experiments were conducted. In Expt. 1, the following six substrates were evaluated: 100% coir (control), 100% peat, 100% pine bark, and peat-bark mixtures of 75%-25%, 50%-50%, and 25%-75%. In Expt. 2, five nitrogen (N)-based (50, 100, 200, 300, and 500 mg L-1 N) fertigation rates were evaluated to determine growth and yield parameters after transplanting. Physical growth parameters, such as the number of tillers, tiller height, relative foliar chlorophyll content, number of roots, emerging tiller node, and fresh and dry weights of tillers, roots, and new rhizomes, were measured. According to the data, no significant differences were observed among the substrates, indicating the adaptation of ginger to a wide range of substrates. In contrast, the fertigation rate significantly influenced all ginger growth parameters except chlorophyll content. Ginger performed better under low fertigation rates (approximately 100 mg L-1 N). For example, the fresh weights of new rhizomes at the 100 ppm N-based nutrient level were 15.8%, 205.3%, 237.0%, and 344.9% higher than those under 50, 200, 300, and 500 ppm N-based fertigation, respectively. Similarly, the dry weights were 28.3%, 183.9%, 371.0%, and sults demonstrate that ginger rhizomes perform better under well-aerated soilless substrates combined with low fertigation rates in controlled environments.

Organic production is becoming increasingly popular among producers in controlled environment agriculture. However, selecting a suitable fertilizer for organic production can be complicated, as commercially available organic fertilizers have widely different nutrient compositions. The goal of this study was to evaluate the effectiveness of several liquid organic fertilizers and compare their performance with a synthetic fertilizer for growing lettuce and dwarf tomato in containerized production systems under a controlled environment. Two consecutive experiments were conducted. In Expt. 1, three commercial liquid organic fertilizers [earthworm castings (F1), sugarcane molasses (F2), and fish emulsion (F3)] were evaluated under two different containerized systems [Dutch bucket (DB) and regular plastic container (RPC)]. The best-performing fertilizers (F1, F2) were then compared with synthetic fertilizer (F4) in Expt. 2. In Expt. 1, lettuce was harvested 14 and 28 days after transplanting to assess shoot growth. In Expt. 2, dwarf tomato was also considered along with the lettuce, which were harvested 60 and 30 days after transplanting, respectively. Besides evaluating the regular growth parameters in both experiments, lettuce leaf tissue and leachate analyses were performed in Expt. 2. In Expt. 1, the F1 fertilizer outperformed F2 and F3, resulting in a 28% and 32% higher fresh weight in the DB system, and a 57% and 41% higher fresh weight in the RPC system, respectively. In addition, F1 led to improvements in the RPC system compared with the DB system, with increases of 28% in fresh weight, 20% in dry weight, 48% in leaf area, 26% in shoot width, 126% in root fresh weight, and 47% in root length. In Expt. 2, results showed that F1 performed similar to or better than F4 for growing lettuce and dwarf tomatoes in container hydroponic systems. Leaf tissue and leachate analyses also showed similar results. The findings of this study indicate that synthetic fertilizer could be replaced by some liquid organic fertilizers, and a single organic fertilizer could be used instead of several for organic leafy green production. Fruit crops such as tomato may require more than one organic fertilizer to provide the correct ratio of all nutrients.

IntroductionNutrient supply in hydroponic leafy green production is often not aligned with crop-specific requirements. Kale (Brassica oleracea ‘Red Russian’) has been shown to exhibit higher nitrogen (N) demand than other leafy greens. Conventional nutrient management relies on a two-part water-soluble fertilizer system—Part A with macronutrients and micronutrients and Part B with calcium nitrate (Ca(NO3)2)—to maintain electrical conductivity (EC), but this approach may not optimize N supplementation or crop quality.MethodsWe evaluated a modified protocol in which only Ca(NO3)2 was supplied during the final production week, replacing the standard two-part adjustment. Plant biomass, nutrient composition, phytochemicals, and physiological traits of hydroponically grown kale were assessed.ResultsThe Ca(NO3)2-only treatment significantly increased shoot biomass, shoot-to-root ratio, and uptake of N, calcium, and magnesium by 28.5%, 22.1%, 46.0%, 27.5%, and 14.4%, respectively, compared with conventional management, suggesting N and calcium were key limiting factors for shoot growth. Nitrate accumulation in shoots also increased but remained within safe consumption limits. Phytochemical analysis revealed reductions in anthocyanins and vitamin C, alongside a slight increase in glucosinolates. No significant changes were observed in photosynthetic traits, root growth, or water and acid use.DiscussionTargeted N supplementation with Ca(NO3)2 enhanced growth and nutrient uptake in kale but introduced tradeoffs in phytochemical composition. These results underscore the potential of crop-specific nutrient strategies to improve both yield and nutritional quality of hydroponic leafy greens in controlled environment systems.

Greenhouse tomato production faces multiple challenges, including the excessive use of nonrenewable substrates that are difficult to dispose of after use. Currently, most growers propagate tomatoes in rockwool, but there is an increasing demand for sustainable media. The objective of this research was to evaluate sustainable and organic alternatives for greenhouse propagation of tomato seedlings intended for high-wire production. Different organic and inorganic substrates were evaluated in three experiments, using a nutrient solution composed of a complete water-soluble fertilizer. Germination and growth parameters, including height, stem diameter, number of leaves, leaf area, foliar chlorophyll levels (SPAD), and shoot fresh and dry weight, were measured. In the first experiment, which employed overhead irrigation, rockwool, coir, wood fiber–coir mix, medium-grade pine bark, pine bark < 0.64 cm, and pine bark < 0.32 cm were evaluated. Tomato germination was faster and achieved higher percentages with pine bark < 0.64 cm compared to other substrates. However, growth performance was similar or better in coir than in rockwool four weeks after transplantation. For the second experiment with sub-irrigation only, rockwool, coir, wood fiber–coir mix, pine bark < 0.32 cm bark, and peat were evaluated at different container heights. Peat resulted in greater growth across all parameters, followed by wood fiber–coir mix in all container heights, while pine bark had the least growth across all measured parameters. In the third experiment with overhead irrigation, rockwool, wood fiber–coir mix, pine bark < 0.32 cm, and a commercial peat-based mixture were evaluated under different fertilizer rates (electrical conductivity of 1.1 and 2.2 mS·cm−1). Wood fiber–coir mix, peat-based mix, and rockwool were the substrates with the highest values for all evaluated parameters. While all the organic substrates showed potential for use in tomato propagation, pine bark < 0.32 cm bark and wood fiber–coir mix provided the best media for germination. Peat and wood fiber–coir mix showed the best media for subsequent seedling growth and demonstrated potential to be used as substitutes for rockwool.

Kale (Brassica napus) and collard (Brassica oleracea) are two leafy greens in the family Brassicaceae. The leaves are rich sources of numerous health-beneficial compounds and are commonly used either fresh or cooked. This study aimed to optimize the nutrient management of kale and collard in hydroponic production for greater yield and crop quality. ‘Red Russian’ kale and ‘Flash F1’ collard were grown for 4 weeks after transplanting in a double polyethylene-plastic-covered greenhouse using a nutrient film technique (NFT) system with 18 channels. Kale and collard were alternately grown in each channel at four different electrical conductivity (EC) levels (1.2, 1.5, 1.8, and 2.1 mS·cm−1). Fresh and dry yields of kale increased linearly with increasing EC levels, while those of collard did not increase when EC was higher than 1.8 mS·cm−1. Kale leaves had significantly higher P, K, Mn, Zn, Cu, and B than the collard at all EC levels. Additionally, mineral nutrients (except N and Zn) in leaf tissue were highest at EC 1.5 and EC 1.8 in both the kale and collard. However, the changing trend of the total N and NO3- of the leaves showed a linear trend; these levels were highest under EC 2.1, followed by EC 1.8 and EC 1.5. EC levels also affected phytochemical accumulation in leaf tissue. In general, the kale leaves had significantly higher total anthocyanin, vitamin C, phenolic compounds, and glucosinolates but lower total chlorophylls and carotenoids than the collard. In addition, although EC levels affected neither the total chlorophyll or carotenoid content in kale nor glucosinolate content in either kale or collard, other important health-beneficial compounds (especially vitamin C, anthocyanin, and phenolic compounds) in kale and collard leaves reduced with the increasing EC levels. In conclusion, the kale leaf had more nutritional and phytochemical compounds than the collard. An EC level of 1.8 mS·cm−1 was the optimum EC level for the collard, while the kale yielded more at 2.1 mS·cm−1. Further investigations are needed to optimize nitrogen nutrition for hydroponically grown kale.

Organic farming methods, including the use of organic substrates, fertilizers, pesticides, and biological control, are gaining popularity in controlled environment agriculture (CEA) due to economic benefits and environmental sustainability. However, despite several studies focusing on the preparation and evaluation of liquid organic fertilizers, none have explored the compatibility of these fertilizers with different hydroponic systems. Therefore, the objective of this study was to evaluate lettuce production using a liquid organic fertilizer under different hydroponic systems. Four distinct hydroponic methods were selected: nutrient film technique (NFT), deep water culture (DWC) (liquid culture systems), and Dutch bucket (DB), regular plastic container (RPC) (substrate-based systems). ‘Green Butter’ lettuce was grown using a liquid organic fertilizer (Espartan) for four weeks. Shoot growth parameters (e.g., shoot width, number of leaves, leaf area, foliar chlorophyll content, fresh weight, and dry weight) and root growth parameters (e.g., root length, fresh weight, and dry weight) were measured. The growth difference of lettuce under the DB and RPC systems was negligible, but the growth in RPC was 29% to 60% and 15% to 44% higher than the NFT and DWC systems, respectively, for shoot width, number of leaves, leaf area, shoot fresh weight and dry weight. Root parameters were nearly identical for the NFT and DWC systems but significantly lower (21% to 94%) than the substrate-based DB and RPC systems. Although lettuce grown in the NFT system showed the least growth, its mineral content in the leaf tissue was comparable or sometimes higher than that of substrate-based hydroponic systems. In conclusion, the tested liquid organic fertilizer is suitable for substrate-based hydroponic systems; however, further evaluation of different liquid organic fertilizers, and crop species is required.

Two hydroponic system designs (nutrient film technique: NFT, and deep water culture: DWC) were set up in a climate-controlled greenhouse to compare growth, nutrients and water uptake patterns, yield and quality of lettuce (Lactuca sativa cv. Butterhead) during fall (October through November) and summer (July-August) growing conditions. The research was conducted with four system replicates for each hydroponic design and each system contained nine lettuce plants. Plant photosynthetic properties, growth parameters, and irrigation solution nutrient concentrations were measured weekly. At the end of the production cycle, plants were harvested for leaf area, fresh and dry yield of shoots and roots, nutritional and phytochemical concentrations. In the study, DWC system had better water quality properties than NFT including less seasonal water temperature fluctuation, which supported lettuce with better photosynthetic rates, growth rate and fresh yield in fall. Tipburn symptoms were only observed in summer, and NFT grown lettuce had significantly lower shoot calcium and magnesium concentrations than DWC in both fall and summer seasons, which led to more severe tip burn symptom in summer. In addition, better water quality in DWC also benefited lettuce with higher antioxidant concentrations than NFT, which included 9.4 % higher vitamin C in fall, 34.6 % higher total carotenoids in fall, 40.6 % higher non-acidified phenols in fall, as well as 12.9 % higher total chlorophyll in summer. Although there were marginal differences in fresh yield, most types of mineral nutrients and antioxidants between DWC and NFT, DWC performed better than NFT with less tipburn in summer as well as increased yield, total carotenoids, vitamin C and non-acidified phenols in fall.

Two hydroponic production system designs (nutrient film technique: NFT, and deep-water culture: DWC) were set up in a climate-controlled greenhouse aiming to investigate differences in growth, nutrient and water uptake patterns, yield and quality of lettuce (Lactuca sativa 'Butterhead') between the two systems. The research was conducted from July through August (summer growing conditions) with four system replicates for each hydroponic design and each system contained nine lettuce plants. Throughout the study, photosynthetic properties were higher in NFT-grown lettuce than DWC. Leaf area, fresh yield, and dry yield were higher in NFT by 13.0, 22.8 and 27.7%. All leaf nutrients except calcium and magnesium in shoot tip were within the sufficiency range for lettuce in both systems. In the nutrient solution of both systems, nitrogen, phosphorus and potassium concentrations decreased, while calcium, magnesium, and sulfur concentrations gradually increased throughout the study. There was higher percentage of nitrogen, calcium and sulfur uptake in NFT than DWC by 9.2%, 31.4 and 33.9%. Total chlorophyll and total carotenoid concentrations in NFT-grown lettuce were lower than DWC-grown lettuce by 5.2 and 41.0%, respectively. Total water consumption was 9.6% higher in NFT than in DWC which explains the increased accumulation of some ions in NFT. In conclusion, although 30% yield increase was observed with NFT, total chlorophyll and total carotenoid contents were greater in DWC.

Clematis (Clematis ×hybrida) has not traditionally fit into the standard production system for vegetatively propagated herbaceous perennials because of the lack of commercially available unrooted cuttings and relatively poor rooting success. We investigated strategies to improve stock plant production and propagation of clematis. The first experiment compared the propagation performance of four cultivars (H.F. Young, Reiman, Little Duckling, and Pinky). The second experiment examined cutting productivity and propagation performance of clematis cultivars when stock plants were grown at 21 or 27 °C and propagated with or without the application of rooting hormone. Stock plants grown at 27 °C resulted in greater cutting numbers and greater dry weights in the rooted cuttings after propagation. The third experiment demonstrated the effects of the origin of the cuttings of the stock plant on cutting productivity and propagation performance. When shoots emerged from underground buds, as compared with axillary buds, the numbers of cuttings and fresh and dry weights of the rooted cuttings were increased by nearly 50%. The promotion of shoot emergence from underground buds on the stock plants led to continuous cutting production for five cycles, with cutting number increasing from 67 to 128 cuttings/plant. Year-round cutting supplies can be achieved by trimming stock plants to the substrate surface to promote juvenile shoot development while maintaining stock plants under long-day photoperiods and warm temperatures (27 °C).

Arugula (Eruca sativa) is cultivated using hydroponic techniques in greenhouses to fulfill high year-round demand, but its nutrient management in hydroponic production has not yet been standardized, potentially leading to limited quality and productivity. Aiming to address this issue, we investigated the effect of electrical conductivity (EC) on yield, nutritional and phytochemical properties of arugula. The model cultivar arugula ‘Standard’ was grown at four different EC levels (1.2, 1.5, 1.8, and 2.1 dS·m−1). Our results indicated photosynthetic properties, SPAD, leaf area, yield and dry weight increased with increasing EC from 1.2 to 1.8 dS·m−1. Foliar nutrient content increased with higher EC, but nutrient solution with 2.1 dS·m−1 showed a significant decline in N, Ca and most of the micronutrients including Fe, Zn, Mo, Cu, B and Mn. Total glucosinolates, total chlorophyll and total carotenoids concentrations increased with increasing EC. In addition, total anthocyanin content was highest in plants grown in EC 1.2 and 2.1 dS·m−1, demonstrating a stress response when grown in extreme EC levels. Our results further indicated a rapid accumulation of nitrate with higher EC, potentially detrimental to human health. This research demonstrated the optimal EC range would be 1.5 to 1.8 dS·m−1 for arugula in hydroponic production systems based on yield, quality criteria and human health considerations.

Clematis (Clematis ×hybrida) is among the flowering plants well-recognized by the retail consumer; however, production has not traditionally fit into standard greenhouse production systems. One reason is the relatively long 2-year production cycle from propagation to flowering. Four experiments were conducted with clematis ‘H.F. Young’ to understand the factors that influence shoot development and flowering of clematis so that strategies could be developed for bulking, providing a cold treatment, and flowering the plants with a shortened production time. The first experiment showed an increase in shoot and flower numbers and a decrease in time to flower as the duration of cold treatment increased from 0 to 9 weeks and the photoperiod increased from 9 to 16 hours. The second experiment resulted in greater shoot and flower numbers when plants were forced at 21 °C as compared with 27 °C. The third experiment showed that the application of ethephon (500 or 1000 mg·L−1) during bulking increased shoot formation (branching) as compared with the control or 500 mg·L−1 benzylaminopurine treatments. The fourth experiment showed that applications of 500 mg·L−1 ethephon along with a 16-hour photoperiod during the bulking period improved shoot number and flowering of the finished crop. The combined results provide guidelines for producing a well-branched, flowering clematis crop within 1 year from the start of propagation to the time of the first open flower.