Search Results
.1080/00221589.1984.11515216 Jones J.B. Jr 1997 Hydroponics: A practical guide for the soilless grower St. Lucie Press Boca Raton, Fla Lee, S.K. Kader, A.A. 2000 Preharvest and postharvest factors influencing vitamin C content of horticultural crops Postharvest Biol. Technol. 20 207
In growing greenhouse tomato (Lycopersicon esculentum Mill.) using the nutrient film technique (NFT), HNO3 or H3PO4 is usually added to offset the increase in pH of the recirculating solution. For economic and environmental reasons, HCl would be a possible substitute for either HNO3 or H3PO4. Therefore, experiments were initiated to evaluate HCl as an alternative acid in controlling the pH of the recirculating solution in NFT-grown greenhouse tomato. The effects of HNO3, H3PO4, and HCl on the growth, fruit yield, and fruit quality were quantified. In 1995, these effects were tested using `Trust' and `BST 7804' at a recirculating solution pH of 5.5, 6.0, or 6.5; in 1996, only `Trust' was grown at a recirculating solution pH of 6.2. In the 1995 experiment, genotypic differences in marketable fruit yield tended to be smaller when HCl was used to control the recirculating solution pH at 6.0 than when either H3PO4 or HNO3 was used. In `Trust', at a pH of 5.5 under the HCl treatment, fruit quality tended to be higher than in other treatment combinations. In 1996, over a 45-day period, the concentration of Cl− that accumulated in the recirculating solution from added HCl was 313 mg·L−1 (313 ppm). There were no significant effects of the treatments on the growth, fruit quality, or yield of the crop. The total marketable yield was better when HCl had been used, likely due to high fruit production at the early part of the harvesting period. Potential savings for the season can be achieved if HCl is substituted for H3PO4 to regulate the nutrient solution pH in NFT-based greenhouse tomato production.
biological demand requires greater inputs of oxygen to sustain homeostasis ( Ben-Noah and Friedman, 2018 ). The nutrient solution of liquid hydroponics benefits from levels of DO close to saturation near 8 mg⋅L –1 . This promotes healthy root respiration and
Greenhouse experiments were conducted in 2005 and 2006 near Live Oak, FL, to develop fertilization programs for fresh-cut ‘Nufar’ basil (Ocimum basilicum) and spearmint (Mentha spicata) in troughs with soilless media using inputs compliant with the U.S. Department of Agriculture's National Organic Program (NOP). Four NOP-compliant fertilizer treatments were evaluated in comparison with a conventional control. Treatments and their analyses in nitrogen (N), phosphorus (P), and potassium (K) contents are as follows: conventional hydroponic nutrient solution [HNS (150 ppm N, 50 ppm P, and 200 ppm K)], granular poultry (GP) litter (4N–0.9P–2.5K), granular composite [GC (4N–0.9P–3.3K)], granular meal [GM (8N–2.2P–4.1K)], and GM plus a sidedress application of 5N–0.9P–1.7K fish emulsion (GM + FE). Electrical conductivity (EC) of the media, fresh petiole sap nitrate (NO3-N) and K concentrations, dried whole leaf NO3-N, P, and K concentrations, and yield and postharvest quality of harvested herbs were evaluated in response to the treatments. Basil yield was similar with HNS (340 g/plant) and GP (325 g/plant) in 2005 and greatest with HNS (417 g/plant) in 2006. Spearmint yield was similar with all treatments in 2005. In 2006, spearmint yields were similar with the HNS and GP yields (172 and 189 g/plant, respectively) and greater than the yields with the remaining treatments. In both years and crops, media EC values were generally greater with the GC than with the GP, GM, and GM + FE treatments but not in all cases and ranged from 1.77 to 0.55 dS·m−1 during the experiments. Furthermore, HNS media EC values were consistently equal to or lower than the GP media EC values except with EC measurements on 106 days after transplanting in both crops in 2005. Petiole NO3-N and K results were variable among crops and years, but provided valuable insight into the EC and yield data. We expected EC, petiole NO3-N, and petiole K to be consistently higher with HNS than with organic treatments, but they were not, indicating a reasonable synchrony of nutrient availability and crop demand among the organic treatments. The postharvest quality of both basil and spearmint was excellent with all treatments with few exceptions.
Rockwool is an excellent growing medium for the hydroponic production of tomato; however, the standard size rockwool blocks [4 × 4 × 2.5 inches (10 × 10 × 6.3 cm) or 3 × 3 × 2.5 inches (7.5 × 7.5 × 6.3 cm)] are expensive. The following experiments were conducted with less expensive minirock wool blocks (MRBs), on rayon polyester material (RPM) as a bench top liner, to reduce the production cost of tomatoes (Lycopersicon esculentum) grown in a limited-cluster, ebb and flood hydroponic cultivation system. Fruit yield for single-cluster plants growing in MRBs [2 × 2 × 1.6 inches (5 × 5 × 4 cm) and 1.6 × 1.6 × 1.6 inches (4 × 4 × 4 cm)] was not significantly different from plants grown in larger sized blocks (3 × 3 × 2.5 inches). When the bench top was lined with RPM, roots penetrated the RPM, and an extensive root mat developed between the RPM and the bench top. The fruit yield from plants on RPM was significantly increased compared to plants without RPM due to increases in fruit size and fruit number. RPM also significantly reduced the incidence of blossom-end rot. In a second experiment, single- and double-cluster plants were grown on RPM. Fruit yield for double-cluster plants was 40% greater than for single-cluster plants due to an increase in fruit number, although the fruit were smaller in size. As in the first experiment, fruit yield for all plants grown in MRBs was not significantly different from plants grown in the larger sized blocks. MRBs and a RPM bench liner are an effective combination in the production of limited-cluster hydroponic tomatoes.
Cucumbers (Cucumis sativus L. `Vetomil') were grown in rockwool or perlite to evaluate these media for efficient hydroponic cucumber production under Florida greenhouse conditions. Plants were grown using a double-stem training method, and the frequency of irrigations was controlled by a weighing lysimeter for each treatment. In Expt. 1, plants were grown in rockwool with 29% or 17% leaching fraction (LF) and in perlite with a 17% LF. Nitrogen, P, and K concentrations in the complete nutrient solution were 175, 50, and 180 mg·L−1, respectively. In Expt. 2, N, P, and K concentrations were increased to 225, 60, and 225 mg·L−1, respectively. Other nutrient concentrations and LFs remained as in Expt. 1. In Expt. 1, yields (fruit count and total fruit mass) were higher from plants grown in rockwool at 29% LF than from plants grown in rockwool or perlite at 17% LF. However, in Expt. 2, when nutrient concentrations were higher, total fruit mass was greater from plants grown at the lower LF, although there was no difference in fruit number. In both experiments, cucumber yield did not differ when grown at the same LF in either rockwool or perlite. Electrical conductivity (EC) and pH of the nutrient solution from the growing bags were not affected when LFs were decreased. In Expt. 1, the pH and EC ranged from 6.1 to 7.0 and from 0.9 to 1.6 mS·cm−1, respectively, across all treatments. In Expt. 2, pH and EC ranged from 5.3 to 6.9 and from 0.6 to 2.5 mS·cm−1, respectively, across all treatments.
Four experiments were conducted from 1992 to 1994 to determine the concentrations of N and P required to maximize yields of rockwool-grown cucumbers (Cucumis sativus `Vetomil') trained with a double-stem method. Concentrations of N and P in rockwool slabs were monitored throughout growth of greenhouse-grown cucumbers. The onset and duration of nutrient depletion in the slabs were related to cucumber yield. In Expt. 1, treatment-1 plants received a two-step solution containing N at 90 and 175 mg·L−1 during successive growth phases, while treatment-2 and -3 plants were grown with N at a constant 175 or 225 mg·L−1. Phosphorus was provided at 50 mg·L−1 in all treatments. Treatment 1 was excluded from Expt. 2. In Expts. 3 and 4, plants were grown with N at 225 or 275 mg·L−1 and P at 75 mg·L−1. Onset of N and P depletion (to <10 mg·L−1) in the growing slabs occurred during the early fruiting stage of cucumber, 1 to 8 days before first harvest. The duration of N and P depletion decreased, and cucumber yields increased with increasing N and P concentrations. When plants were grown with N and P at 275 and 75 mg·L1, respectively, N was depleted in the growing slabs during only one experiment and then for only 4 days, and slab P concentration remained >10 mg·L1. Therefore, under Florida conditions, when growing cucumbers in rockwool using a double-stem training technique, N and P should be provided at 275 and 75 mg·L−1, respectively, to minimize depletion of these nutrients from the growing medium.
Bahiagrass (Paspalum notatum) is widely used for slope protection and water and soil conservation in southern China. The plants develop an extensive root system that plays a crucial role in the protection of both soil and water. However, little is currently known about the factors that influence early root growth in bahiagrass. Here, the effects of boron (B), calcium (Ca), iron (Fe), lanthanum (La), cerium (Ce), salicylic acid (SA), and melatonin (MLT) on root growth characteristics were examined. Bahiagrass seedlings were grown in 1/25 strength modified Hoagland nutrient solution supplemented with boric acid, calcium chloride, ferric ethylenediaminetetraacetic acid (Fe-EDTA), lanthanum chloride, cerium chloride, SA, or MLT. Root lengths, root surface areas, and the number of root tips were analyzed using a root scanning system after 2, 4, and 6 days of treatment. We found significant effects on root growth after some treatments. Thus, 0.270 or 0.360 mm B for 2 days enhanced root tip number, whereas 0.15 mm Fe for 6 days increased root surface area. Although 3 or 5 mm Ca caused an increase in root tip numbers, the root length was reduced. The addition of La to the nutrient solution significantly increased root length and surface area, and addition of Ce increased root surface area and root tip numbers. Root growth characteristics were optimal after 0.3 μm La for 6 days or 1.0 μm La for 4 days. For Ce treatment, optimal root characteristics were observed at 0.5 μm Ce for 6 days. Root tip numbers increased after 0.1 or 1.0 μm MLT for 6 days, whereas SA treatment reduced the root length, surface area, and root tip numbers. Overall, the analyses indicate that treatment with B, Fe, La, Ce, and MLT benefited root growth in bahiagrass seedlings.
Completely enclosed screen houses can physically exclude contact between the asian citrus psyllid [ACP (Diaphorina citri)] and young, healthy citrus (Citrus sp.) trees and prevent huanglongbing (HLB) disease development. The current study investigated the use of antipsyllid screen houses on plant growth and physiological parameters of young ‘Ray Ruby’ grapefruit (Citrus ×paradisi) trees. We tested two coverings [enclosed screen house and open-air (control)] and two planting systems (in-ground and container-grown), with four replications arranged in a split-plot experimental design. Trees grown inside screen houses developed larger canopy surface area, canopy surface area water use efficiency (CWUE), leaf area index (LAI) and LAI water use efficiency (LAIWUE) relative to trees grown in open-air plots (P < 0.01). Leaf water transpiration increased and leaf vapor pressure deficit (VPD) decreased in trees grown inside screen houses compared with trees grown in the open-air plots. CWUE was negatively related to leaf VPD (P < 0.01). Monthly leaf nitrogen concentration was consistently greater in container-grown trees in the open-air compared with trees grown in-ground and inside the screen houses. However, trees grown in-ground and inside the screen houses did not experience any severe leaf N deficiencies and were the largest trees, presenting the highest canopy surface area and LAI at the end of the study. The screen houses described here provided a better growing environment for in-ground grapefruit because the protective structures accelerated young tree growth compared with open-air plantings while protecting trees from HLB infection.