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., 2015 ; Polat et al., 2004 ; Silber and Raviv, 1996 ). Accordingly, using 0 to 4-mm substrate holds promise for improving growth and flower quality of asiatic hybrid lily grown under soilless culture. Units Literature cited Adams, P. 2002 Nutritional
Two greenhouse cucumber (Cucumis sativus) cultivars with differing fruit types [European (`Bologna') and Beit-alpha (`Sarig')] were grown during two seasons in a perlite medium in black plastic nursery containers in a passively ventilated greenhouse in northern Florida to evaluate fruiting responses to nitrogen (N) fertilization over the range of 75 to 375 mg·L–1. Fruit production, consisting mostly of fancy fruits, increased quadratically with N concentration in the nutrient solution, leveling off above 225 mg·L–1 for both cucumber cultivars. Fruit length and diameter were not affected by N concentration in the nutrient solution. Leaf N concentration, averaged over three sampling dates, increased linearly with N concentration in the nutrient solution from 46 g·kg–1 with 75 mg·L–1 N to 50 g·kg–1 with 375 mg·L–1 N. Fruit firmness decreased with increasing N concentration and there was little difference in firmness between the two cultivars. Firmness was similar across three measurement dates during the spring harvest season, but increased during the season in the fall. Fruit color responses to N concentration were dependent on the specific combination of experiment, sampling date, and cultivar. For most combinations of experiment, sampling date, and cultivar, cucumber epidermal color was greener (higher hue angle) with increased N concentration. The color was darkest (lowest L* value) and most intense (highest chroma value) with intermediate to higher N concentrations.
A very practical definition of “soilless culture” is the growth of nonaquatic plants with roots in a substrate without mineral soil, where plant nutrient needs are supplied with a nutrient solution. Soilless culture has various classification
. Raviv and J.H. Lieth (eds.). Soilless culture, theory and practice. Elsevier, London, UK 10.1016/B978-044452975-6.50011-3 Blok, C. Jackson, B.E. Guo, X. de Visser, P.H. Marcelis, L.F. 2017 Maximum plant uptakes for water, nutrients, and oxygen are not
that their growth was significantly reduced in a soilless culture compared with culturing in soil. Previous studies offered explanations of this phenomenon, including mechanical resistance that impedes root growth ( Zobel, 1991 ), presence of light
A solid-matrix-over-liquid (hybrid) growth system was developed for direct sowing of small-seeded crop species into hydroponic culture and compared for performance with a standard solid-matrix, capillary-wick hydroponic system. Seeds were sown directly onto a 3-cm (1.2-inch) deep soilless seed bed occupying 0.147 m2 (1.582 ft2) within a tray. The planted seed bed was moistened by wicking up nutrient solution through polyester wicking material from a 7.0-L (6.6-qt) reservoir just below the matrix seed bed. The hybrid system successfully grew dense [435 plants/m2 (40.4 plants/ft2)], uniform canopies of dwarf Brassica napus L. in a controlled-environment growth room. Seed yield using the hybrid system was twice that achieved with the matrix-based system. Both systems eliminated the labor needed to transplant many small seedlings from a separate nurse bed into a standard bulk liquid hydroponic system. Root-zone pH extremes caused by ion uptake and exchange between roots and unrinsed soilless media were avoided for the hybrid system by the short dwell time of roots in the thin matrix before they grew through the matrix and an intervening headspace into the bulk solution below, where pH was easily managed. Once roots grew into the bulk solution, its level was lowered, thereby cutting off further capillary wicking action and drying out the upper medium. Beyond early seedling establishment, water and nutrients were provided to the crop stand only by the bulk nutrient solution. This hybrid hydroponic system serves as a prototype for largerscale soilless growth systems that could be developed for production of smallseeded crops in greenhouses or controlled environments.
Mini or “baby” vegetables have become increasingly popular items for restaurant chefs and retail sales. Squash (Cucurbita pepo) are generally open-field cultivated where climate, insect, and disease pressures create challenging conditions for growers and shippers who produce and market this delicate, immature fruit. In order to overcome these challenges, in Spring 2003 and 2004, 18 squash cultivars, including zucchini, yellow-summer, patty pan/scallop, and cousa types, were grown hydroponically in a passively ventilated greenhouse and compared for yield of “baby”-size fruit. Squash were graded as “baby” when they were less than 4 inches in length for zucchini, yellow-summer, and cousa types and less than 1.5 inches diameter for round and patty pan/scallop types. In both seasons, `Sunburst' (patty pan) produced the greatest number of baby-size fruit per plant, while `Bareket' (green zucchini) produced the least. The zucchini-types produced between 16 and 25 baby-size fruit per plant in 2003. The yellow summer squash-types produced on average 45 baby fruit per plant. The production of the patty pan/scallop types ranged from 50 to 67 baby-size fruit per plant depending on cultivar. The cousa types produced approximately 30 baby-size fruit. Total yields were lower in 2004 due to a shortened season. Squash plants will produce numerous high quality baby-sized fruit when grown hydroponically in a reduced pesticide environment of a greenhouse where they can be harvested, packaged, and distributed to buyers daily. The cultivars Hurricane, Raven, Gold Rush, Goldy, Sunray, Seneca Supreme, Supersett, Butter Scallop, Sunburst, Patty Green Tint, Starship, Magda, and HA-187 could be used for hydroponic baby squash production.
The evolution of plastic uses (excluding glazing) in the production of greenhouse vegetables is presented. Plastics are used in almost every aspect of crop production, including providing a barrier to the soil, lining crop production troughs, holding soil and soilless media, and providing a nutrient film channel. Irrigation systems have become very elaborate, with various plastic products used to transport water and nutrients and to provide a means of emitting nutrient solution to the crop. The greenhouse environment is managed from several plastic components, including air distribution tubes, shade materials, and energy curtains. Plastics are now common in greenhouse vegetable crop training, insect monitoring, postharvest handling, storage, and marketing.
Plants can synthesize some antioxidants, including L-ascorbic acid (AsA) and polyphenol, in response to environmental stresses. Antioxidants detoxify reactive oxygen species in plants and also aid in human health. In this study, we demonstrate that a novel hydroponic treatment can increase leafy vegetable nutritional quality without retarding growth. Leaf lettuce (Lactuca sativa) was grown hydroponically and subjected to rhizosphere drought stress by lowering the water level in the solution tub before harvesting. Appropriate drought stress using this method could increase AsA, polyphenol, and sugar content by 24%, 50%, and 17%, respectively, and decrease nitrate nitrogen content by 18% without reducing yield. Similar effects of drought stress on AsA content were observed in four other plant species. This hydroponic method has a universal potential to increase leafy vegetable quality without reducing yield in controlled environments such as plant factories.
Production and quality of bell pepper (Capsicum annuum) fruit were evaluated in a passively ventilated greenhouse, in soilless media trellised to a “V” system (two-stempruned plants) or the “Spanish” system (nonpruned plants) in flat bags or nursery pot containers; and densities of 1.5, 1.9, 3.0, and 3.8 plants/m2 (0.14, 0.18, 0.28, and 0.35 plants/ft2), in a winter-to-summer-crop in Gainesville, Fla. The trellis systems did not affect total marketable fruit yields but production of extra-large fruit was higher (38%) in non-pruned than in pruned plants. Marketable fruit yields were similar in plants grown in bags and pots, and had positive linear responses to increased plant density. Not pruning reduced by half the percentage of fruit with blossom-end rot. Pruned plants produced 50% fewer flower bud supporting nodes than non-pruned plants but had a greater percentage of fruit set. Regardless of trellis systems, fruit set per plant decreased linearly as plant density increased. Overall, the “Spanish” trellis system at a density of 3.8 plants/m2 resulted in greater yields of extra-large fruit and required 75% less labor than the “V” system to prune and support the plant canopy.