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- Author or Editor: Miguel Urrestarazu x
In recent decades, salinity in the culture of tomatoes has been one of the most studied parameters. This study aimed to evaluate the effect of a moderate increase in salinity, fertigation distribution, and its control using thermography on a soilless culture of grafted tomato. A tomato crop (cv. Ramyle) grafted onto tomato rootstocks (cv. Emperor) was cultivated in coir crop units at the University of Almeria from Nov. 2012 to May 2013. A plot design subdivided with four blocks was used, with salinity values of 2.0 and 2.5 dS·m−1 in the main plots and fertigation distribution systems with either one (DD1) or four (DD4) drip manifolds in the subplots. The crop productivity was measured using total crop yield, commercial value, and size. The quality parameters in the fruits were not significantly affected. Thermographies were used to aid the control of differential transpiration exerted by salinity. The difference in salinity did not significantly affect the total or commercial production. However, despite being grafted plants, there was a statistically significant effect (P ≤ 0.05) on the fruit size distribution when the electrical conductivity (EC) of the nutrient solution was increased from 2.0 to 2.5 dS·m−1, with a lower production (16%) of large fruits and an increased production of smaller fruits. The DD4 system significantly increased large tomato production (22%) compared with DD1, and the quality parameters in the fruits were not significantly affected. As a result of the improvement in tomato size, the DD4 distribution system economically offset the required higher initial expenditure compared with the DD1 system. Thermography was revealed to be a robust, simple, and quick tool for diagnosing the effect of salinity on transpiration.
At present, trends exist in the production of food for the benefit of human health. The negative effect of an excessive intake of nitrates accumulated in vegetables is well known, causing worldwide concern. Light plays an important role in the accumulation of this ion. The objective of this work was to evaluate the effect of light-emitting diode (LED) spectra used in artificial lighting for horticulture on the accumulation of nitrates in leafy and root vegetables compared with the effects with white LED lights. Two independent experiments were carried out in the culture chamber. In Expt. 1, six species of nitrate accumulators were used: arugula, spinach, lettuce, endive, radish, and beetroot. In Expt. 2, four lettuce cultivars were used. In both experiments, the treatments were two spectra—T1 = AP67 Valoya® and the control (T0) = white Roblan®—at two illumination intensities [high (H) and low (L)] with a 16/8-hour (day/night) photoperiod. The fresh biomass and the concentration of nitrates were measured at 35 days of treatment posttransplantation. An important and significant increase of 50% of the mean fresh weight was obtained in all the species when the light intensity increased. Except for spinach in the low-intensity treatment, all nitrate content values were less than the maximum limits of European regulation. The nitrate content generally decreased with increasing intensity, and this benefit was greater in the T1 treatment. T0 showed a reduction in the nitrate content compared with T1 in only one case, which was the H in beetroot. A large and significant reduction was observed in the nitrate content in T1. For L in Expt. 1, the nitrate decrease was 18%, whereas for H, it was 35%. In Expt. 2, the decrease in the nitrate content was 10% for L and 21% for H. A greater benefit was derived when using the photosynthetic spectrum in the growing chambers under low light intensity.
The response of root growth in containers has been studied in recent decades. The objective was to evaluate the effect of four types of containers on root and shoot growth. The containers were two shapes, round and square, and in some containers, internal vertical walls (IVWs) were placed that increased the internal container surface area with two substrates: perlite and coir fiber. Seedlings of cucumber, pepper, and tomato were transplanted. Two experiments were performed: vegetative growth and drought stress by partial decapitation and a period without fertigation. After decapitation, preexisting and new leaf area, dry biomass or the leaves, and stem were measured. The results revealed that the type of container had no effect, nor were there significant differences between substrates. The containers with IVWs exhibited an increase in biomass and the root surface. The total contact surface with the substrate of the four container types was closely related to the recorded plant growth. Thus, IVWs not only decrease mechanical problems of roots by preventing spiralling but also favor the production of biomass in vegetable plants and substantially increase the root, enabling the plants to manage water deficit and potentially improve posttransplant stress.
Changes caused by NaCl salinity on growth, gas exchange, chemical composition, and oxidative stress symptoms have been measured in six olive (Olea europaea L.) cultivars (Casta Cabra, Cornicabra, Frantoio, Ocal, Picual, and Picudo) grown in nutrient solution in a growth chamber pot experiment. Six-month-old plants were transplanted to a sand–perlite culture and irrigated with half-strength Hoagland nutrient solution containing 0 and 200 mm NaCl for 12 weeks. Salinity significantly depressed growth and leaf gas exchange, but to a different degree in each cultivar, Picudo was the cultivar that showed less growth inhibition. The effectiveness of Na+ exclusion mechanism in the roots differed significantly among studied cultivars, working effectively in ‘Ocal’ and ‘Picudo’ and being less efficient in ‘Picual’. Furthermore, ‘Picudo’ showed the ability to maintain the concentration of leaf K+ under the stress condition. ‘Ocal’ accumulated phenolic compounds and did not reduce carotenoid or total thiol concentration under saline stress. Between the cultivars studied, ‘Picudo’ and ‘Ocal’ were the most tolerant.
The aim of this study was to evaluate the remediation of ferric chlorosis using by iron (Fe)-o,o-EDDHA in fertigation of soilless crops compared with Fe-EDTA (ethylene diamine tetra acetic acid) and its effects on production. Two separate greenhouse experiments were conducted in slab or bag cultures using the tomato (Lycopersicon esculentum Mill. cv. Daniela) and green bean crops (Phaseolus vulgaris L. cv. Maite) in Almería (southeast Spain). The crops were subjected to the following experimental setup: 1) At first phase, all plants were treated with a standard nutrient solution and Fe was supplied as Fe-EDTA. 2) No Fe was supplied in the nutrient solution to bean crops 46 days after transplanting. For tomato plants, this element was eliminated from the nutrient solution since 102 days after transplanting. In this phase, Fe-EDTA was supplied to the control plants (T1). This phase was ended when signs of ferric chlorosis appeared on the leaves. 3) The ferric chlorosis was remediated with either Fe-EDTA (T2) or Fe-o,o-EDDHA (T3). The T4 group did not receive any supplements. The total tomato and bean production was improved after the Fe deficiency had been corrected by either EDTA and Fe o,o-EDDHA supplements in the fertigation of these crops. The synthetic Fe o,o-EDDHA chelate alleviated Fe deficiency by increasing the amount of iron in the rhizosphere and its supply to the leaves and petioles. Consequently, the decrease in tomato and bean production resulting from ferric chlorosis could be prevented. As a conclusion, the remediation of ferric chlorosis through fertigation with Fe o,o-EDDHA is as effective as the use of traditional Fe-EDTA.
Light-emitting diode (LED) lamps signify one of the most important advances in artificial lighting for horticulture over the last few decades. The objective of this study was to compare the cultivation of four horticultural plants using a conventional white LED tube (T0) light against one with a good spectral fit to the maximum photosynthetic response (T1) at two intensities. The experiment was carried out with two types of young lettuce, tomato, and bell pepper plants. In a controlled environment chamber, six and four lamps per square meter were used to achieve high (H) and low (L) intensity, respectively. We measured the lighting parameters illuminance (lux) and photosynthetic photon flux (PPF) intensity (µmol·m−2·s−1). The dry and fresh weight, leaf area (LA), and specific index were measured to gauge plant growth. The photosynthetic activity and energy efficiency (EE) were recorded for each species over 60 days of cultivation. The results clearly demonstrate that, compared with conventional LED lamps, the specific horticultural LED lamps with an improved light spectrum increased the EE of the evaluated vegetables by 26%. At both the studied light intensities, plant growth was clearly more closely linked to the spectral fit of the light to the maximum photosynthetic response recorded by McCree (1972) than to PPF or illuminance (lux). We therefore suggest that a specific, detailed spectral distribution study be conducted to predict the effect of the specific quantity and quality of light used in this study on a single parameter of plant growth.
An intercrop is studied here as a new way of farming in soilless systems within a protected environment. To estimate the efficiency of intercropping in this cultivation system, an experiment was conducted to evaluate the effect of the electrical conductivity (EC) of the nutrient solution (2.0, 2.5, and 3.0 dS·m−1) on lettuce and tomato plants and on the agronomic and economic feasibility of the intercrop compared with monoculture. The results indicated that a moderate increase in EC from 2.0 to 3.0 dS·m−1 did not exert any important effect on tomato plant production or quality but did cause a decrease in lettuce yield in both the first and second crops. Intercropping was only feasible for lettuce when the tomato and lettuce plants were transplanted on the same day. The highest tomato (G class) and lettuce yields were achieved at an EC of 2.5 dS·m−1; this condition resulted in the highest intercrop profitability (0.53 €·m−2 more) when compared with tomato monoculture.
The effect of peracetic acid on the vase life and bud opening of cut flowers of Lisianthus was investigated. Eustoma grandiflorum is an attractive cut flower with a considerable length of vase life (usually weeks for freshly harvested stems). It is well known that the addition of sucrose into the vase solution increases significantly the longevity of cut flowers. Two different experiments of vase life were carried out. The first used cultivars of the Mariachi Series: Blue, Green, Blue Picotee, and Pink, whereas the second used Rosita White and Piccolo White 1. The control plants (T1) were supplied with tap water. Treatment 2 (T2) was similar to T1 with the addition of 3% sucrose. In the third (T3) and fourth (T4) treatments, sodium hypochlorite and a stabilized peracetic mixed system (PAA) were added, respectively. The number of flowers that opened from buds between cultivars was significantly different. With the addition of sucrose into the vase solution, a significant increase in longevity was recorded, which was also observed after the addition of both biocides to the respective treatments. This can be extended up to 15% by the addition of sucrose to the vase solution and up to 30% if PAA is incorporated into the vase solution. The results suggest that PAA can be a useful alternative to sodium hypochlorite for vase solutions because it is without the health drawbacks of trihalomethanes. The degradation of PAA is environmentally friendly, because it decomposes to form biodegradable acetic acid and eventually enters the environment as atomic oxygen.
Based on a new structure for plastic culture channels, a new system for soilless culture called New Growing Systems (NGS) has been developed. It is similar to the nutrient film technique (NFT) but with several potential advantages. Each NGS growing channel has five plastic layers and a large number of holes, there is a dripper every 0.5 m above the first layer of plastic, and each dripper supplies the nutrient solution which flows from the second layer over the others to the end. Three separate greenhouse experiments with tomato, cucumber, and sweet pepper using NGS channels were conducted in Almería (southeastern Spain). The oxygen content in the circulating nutrient solutions was determined at different points and different times along the channels of all crops. Depletion of oxygen content in the nutrient solution was lower than NFT channels. Oxygen content in NGS showed some advantages compared to NFT.
Inadequate oxygenation of the nutrient solution (NS) in recirculating hydroponic systems leads to root hypoxia in several plants as a result of low oxygen solubility, and this is most notable in warm climates. Hypoxia affects crop nutrient and water absorption and results in reduced crop yield. However, increased air supply to the NS serves as a source of oxygen for the roots. To evaluate the incorporation of oxygen into the system, we varied the slope of 14-m long containers from 2% to 4% and applied zero, one, two, or three gaps of NS. The channel width measured 10 cm and was equidistant from the end points. The effect of the dissolved oxygen in the NS was measured by the production of a tomato cultivar. The oxygen dissolved in the NS was 5% greater in the channels with a 4% slope compared with those with a 2% slope. The channels that included the gaps incorporated a higher quantity of dissolved oxygen during cultivation. In the middle of the day, the available oxygen was the limiting factor for the yield. The best results were obtained with a steeper slope, and gaps also improved the tomato yield. More rapid changes in NS were associated with a higher quantity of dissolved oxygen.