Hydroponic Common-Bean Performance under Reduced N-Supply Level and Rhizobia Application

This study aims to explore the possibility of a reduced application of inorganic nitrogen (N) fertiliser on the yield, yield qualities, and biological nitrogen fixation (BNF) of the hydroponic common bean (Phaseolus vulgaris L.), without compromising plant performance, by utilizing the inherent ability of this plant to symbiotically fix N-2. Until the flowering stage, plants were supplied with a nutrient solution containing N-concentrations of either a, 100%, conventional standard-practice, 13.8 mM; b, 75% of the standard, 10.35 mM; or c, 50% of the standard, 6.9 mM. During the subsequent reproductive stage, inorganic-N treatments b and c were decreased to 25% of the standard, and the standard (100% level) N-application was not altered. The three different inorganic-N supply treatments were combined with two different rhizobia strains, and a control (no-inoculation) treatment, in a two-factorial experiment. The rhizobia strains applied were either the indigenous strain Rhizobium sophoriradicis PVTN21 or the commercially supplied Rhizobium tropici CIAT 899. Results showed that the 50-25% mineral-N application regime led to significant increases in nodulation, BNF, and fresh-pod yield, compared to the other treatment, with a reduced inorganic-N supply. On the other hand, the 75-25% mineral-N regime applied during the vegetative stage restricted nodulation and BNF, thus incurring significant yield losses. Both rhizobia strains stimulated nodulation and BNF. However, the BNF capacity they facilitated was suppressed as the inorganic-N input increased. In addition, strain PVTN21 was superior to CIAT 899-as 50-25% N-treated plants inoculated with the former showed a yield loss of 11%, compared to the 100%-N-treated plants. In conclusion, N-use efficiency optimises BNF, reduces mineral-N-input dependency, and therefore may reduce any consequential negative environmental consequences of mineral-N over-application

Innovative Cultivation Practices for Reducing Nitrate Content in Baby Leaf Lettuce Grown in a Vertical Farm

The aim of this research is to introduce innovative cultivation practices that result in reduced nitrate levels in baby leaf lettuce grown under vertical farming conditions while maintaining high productivity. For this reason, three experiments were conducted. The first experiment focused on the impact of two “white” light spectra with a blue:green:red:far-red ratio of 14:32:43:10 (BlowRhigh) and 21:34:36:7 (BhighRlow). The second experiment assessed the effects of two nitrogen supply conditions: sufficient total nitrogen (N15) and limited total nitrogen (N5), and foliar biostimulant application. In the third experiment, the impact of replacing the nutrient solution in the N15 treatment with tap water for an additional 24 h (TW24) on leaf nitrate content was examined. Results from the lighting experiment revealed no significant effects on agronomical parameters or nitrate content between the two light spectra. Reducing nitrogen content in the nutrient solution reduced leaf nitrate content but negatively influenced agronomical characteristics. Biostimulant application and replacing the nutrient solution with water reduced leaf nitrate content compared to the control and positively affected growth. The most favorable outcomes were observed in plants supplied with sufficient nitrogen and foliar biostimulant but also cultivated for an additional 24 h with tap water (Sp-N15-TW24)

Fresh Pod Yield, Physical and Nutritional Quality Attributes of Common Bean as Influenced by Conventional or Organic Farming Practices

The aim of the current study wat to comparatively assess the impact of different nitrogen (N) fertilization schemes on fresh pod yield and yield quality in either organically or conventionally grown common beans (Phaseolus vulgaris L.). Prior to common bean crop establishment, the experimental field site was cultivated following either organic (a) or conventional (b) farming practices with a winter non-legume crop (Brassica oleracea var. italica) (BR), or (c) with field bean (Vicia faba sp.) destined to serve as a green manure (GM) crop. At the end of the winter cultivation period the broccoli crop residues (BR) and green manure biomass (GM) were incorporated into the soil and the plots that accommodated the treatments (a) and (c) were followed by an organically cultivated common bean crop, while the conventional broccoli crop was followed by a conventionally cropped common bean crop. Additional to the plant residues (BR), sheep manure (SM) at a rate of 40 kg N ha−1 was also applied to the organically treated common beans, while the plots with a conventionally cropped common bean received 75 kg N ha−1. Organic common bean treated with SM + BR produced smaller pods of higher dry matter and bioactive compound content, responses that are correlated with limited soil N availability. No significant variations were observed on yield components and N levels of pods cultivated under organic (SM + GM) and conventional cropping systems. Pod sugar and starch content was not influenced by the different fertilization practices. In conclusion, we have demonstrated that the combined application of SM + GM can be considered as an efficient N-fertilisation strategy for organic crops of common bean, benefiting their nutritional value without compromising yield

Assessing Salinity Tolerance and Fruit Quality of Pepper Landraces

Soil salinity caused by climate change is a major global issue, especially in regions like the Mediterranean basin. Most commercially cultivated horticultural species, including pepper, are considered to be salt sensitive. However, some underutilized genotypes exhibit high adaptability to adverse environmental conditions, without compromising yield. This study aimed to investigate the effects of salinity stress on the yield, nutrition, and fruit quality of four pepper landraces: JO 109 (Capsicum annuum var. grossum), JO 204 (Capsicum annuum var. grossum), JO 207 (Capsicum annuum var. grossum), and ‘Florinis’. The California cultivar ‘Yolo Wonder’ and the commercial F1 hybrid ‘Sammy RZ‘ were used as controls. The experiment was conducted in the greenhouse facilities of the Laboratory of Vegetable Production at the Agricultural University of Athens. Half of the plants were exposed to a nutrient solution containing NaCl at a concentration that could maintain the NaCl level in the rhizosphere at 30 mM (salt-treated plants), while the remaining plants were irrigated with a nutrient solution containing 0.5 mM NaCl (control plants). Yield and yield quality attributes, such as firmness, titratable acidity (TA), total soluble solids content (TSSC), fruit height, and diameter were recorded. The results revealed that the landraces were more tolerant to salinity than the commercial varieties ‘Yolo Wonder’ and ‘Sammy RZ’. Moreover, subjecting pepper plants to increased salinity resulted in increased fruit quality, manifested by an increase in TSSC and TA

Plant Biostimulants Enhance Tomato Resilience to Salinity Stress: Insights from Two Greek Landraces

Salinity, one of the major abiotic stresses in plants, significantly hampers germination, photosynthesis, biomass production, nutrient balance, and yield of staple crops. To mitigate the impact of such stress without compromising yield and quality, sustainable agronomic practices are required. Among these practices, seaweed extracts (SWEs) and microbial biostimulants (PGRBs) have emerged as important categories of plant biostimulants (PBs). This research aimed at elucidating the effects on growth, yield, quality, and nutrient status of two Greek tomato landraces (‘Tomataki’ and ‘Thessaloniki’) following treatments with the Ascophyllum nodosum seaweed extract ‘Algastar’ and the PGPB ‘Nitrostim’ formulation. Plants were subjected to bi-weekly applications of biostimulants and supplied with two nutrient solutions: 0.5 mM (control) and 30 mM NaCl. The results revealed that the different mode(s) of action of the two PBs impacted the tolerance of the different landraces, since ‘Tomataki’ was benefited only from the SWE application while ‘Thessaloniki’ showed significant increase in fruit numbers and average fruit weight with the application of both PBs at 0.5 and 30 mM NaCl in the root zone. In conclusion, the stress induced by salinity can be mitigated by increasing tomato tolerance through the application of PBs, a sustainable tool for productivity enhancement, which aligns well with the strategy of the European Green Deal

Effects of NaCl and CaCl₂ as Eustress Factors on Growth, Yield, and Mineral Composition of Hydroponically Grown <i>Valerianella locusta</i>

Corn salad (Valerianella locusta) is a popular winter salad, cultivated as an ingredient for ready-to-eat salads. The application of mild salinity stress (eustress) can increase the flavor and reduce the nitrate content of certain crops but, at the same time, a wrong choice of the eustress type and dose can negatively affect the overall productivity. In this research, the effects of different isosmotic salt solutions, corresponding to two different electrical conductivity (EC) levels, were investigated on the yield and mineral composition of hydroponically grown Valerianella locusta “Elixir”. Five nutrient solutions (NS) were compared, including a basic NS used as the control, and four saline NS were obtained by adding to the basic NS either NaCl or CaCl2 at two rates each, corresponding to two isosmotic salt levels at a low and high EC level. Corn salad proved moderately susceptible to long-term salinity stress, suffering growth losses at both low and high EC levels of saline solution, except from the low NaCl treatment. Hence, it appears that mild salinity stress induced by NaCl could be employed as an eustress solution and corn salad could be cultivated with low-quality irrigation water (20 mM NaCl) in hydroponic systems

Agronomic Practices to Increase the Yield and Quality of Common Bean (Phaseolus vulgaris L.): A Systematic Review

Common bean (Phaseolus vulgaris L.) is the most important legume for human consumption worldwide and an important source of vegetable protein, minerals, antioxidants, and bioactive compounds. The N2-fixation capacity of this crop reduces its demand for synthetic N fertilizer application to increase yield and quality. Fertilization, yield, and quality of common bean may be optimised by several other agronomic practices such as irrigation, rhizobia application, sowing density, etc. Taking this into consideration, a systematic review integrated with a bibliometric analysis of several agronomic practices that increase common bean yield and quality was conducted, based on the literature published during 1971&ndash;2021. A total of 250 publications were found dealing with breeding (n = 61), sowing density and season (n = 14), irrigation (n = 36), fertilization (n = 27), intercropping (n = 12), soilless culture (n = 5), tillage (n = 7), rhizobia application (n = 36), biostimulant/biofertilizer application (n = 21), disease management (n = 15), pest management (n = 2) and weed management (n = 14). The leading research production sites were Asia and South America, whereas from the Australian continent, only four papers were identified as relevant. The keyword co-occurrence network analyses revealed that the main topics addressed in relation to common bean yield in the scientific literature related to that of &ldquo;pod&rdquo;, &ldquo;grain&rdquo;, &ldquo;growth&rdquo;, &ldquo;cultivar&rdquo; and &ldquo;genotype&rdquo;, followed by &ldquo;soil&rdquo;, &ldquo;nitrogen&rdquo;, &ldquo;inoculation&rdquo;, &ldquo;rhizobia&rdquo;, &ldquo;environment&rdquo;, and &ldquo;irrigation&rdquo;. Limited international collaboration among scientists was found, and most reported research was from Brazil. Moreover, there is a complete lack in interdisciplinary interactions. Breeding for increased yield and selection of genotypes adapted to semi-arid environmental conditions combined with the suitable sowing densities are important agronomic practices affecting productivity of common bean. Application of fertilizers and irrigation practices adjusted to the needs of the plants according to the developmental stage and selection of the appropriate tillage system are also of high importance to increase common bean yield and yield qualities. Reducing N-fertilization via improved N-fixation through rhizobia inoculation and/or biostimulants application appeared as a main consideration to optimise crop performance and sustainable management of this crop. Disease and weed management practices appear neglected areas of research attention, including integrated pest management

Agronomic Practices to Increase the Yield and Quality of Common Bean (<i>Phaseolus vulgaris</i> L.): A Systematic Review

Common bean (Phaseolus vulgaris L.) is the most important legume for human consumption worldwide and an important source of vegetable protein, minerals, antioxidants, and bioactive compounds. The N2-fixation capacity of this crop reduces its demand for synthetic N fertilizer application to increase yield and quality. Fertilization, yield, and quality of common bean may be optimised by several other agronomic practices such as irrigation, rhizobia application, sowing density, etc. Taking this into consideration, a systematic review integrated with a bibliometric analysis of several agronomic practices that increase common bean yield and quality was conducted, based on the literature published during 1971–2021. A total of 250 publications were found dealing with breeding (n = 61), sowing density and season (n = 14), irrigation (n = 36), fertilization (n = 27), intercropping (n = 12), soilless culture (n = 5), tillage (n = 7), rhizobia application (n = 36), biostimulant/biofertilizer application (n = 21), disease management (n = 15), pest management (n = 2) and weed management (n = 14). The leading research production sites were Asia and South America, whereas from the Australian continent, only four papers were identified as relevant. The keyword co-occurrence network analyses revealed that the main topics addressed in relation to common bean yield in the scientific literature related to that of “pod”, “grain”, “growth”, “cultivar” and “genotype”, followed by “soil”, “nitrogen”, “inoculation”, “rhizobia”, “environment”, and “irrigation”. Limited international collaboration among scientists was found, and most reported research was from Brazil. Moreover, there is a complete lack in interdisciplinary interactions. Breeding for increased yield and selection of genotypes adapted to semi-arid environmental conditions combined with the suitable sowing densities are important agronomic practices affecting productivity of common bean. Application of fertilizers and irrigation practices adjusted to the needs of the plants according to the developmental stage and selection of the appropriate tillage system are also of high importance to increase common bean yield and yield qualities. Reducing N-fertilization via improved N-fixation through rhizobia inoculation and/or biostimulants application appeared as a main consideration to optimise crop performance and sustainable management of this crop. Disease and weed management practices appear neglected areas of research attention, including integrated pest management

Screening local landraces of melon for resilience to salinity stress under hydroponic greenhouse conditions

Water shortage and heat driven evaporation in semi-arid climate, such as Mediterranean, that are mainly ascribed to climate change, introduced salinity as a major stress factor in vegetable crop production. Thus, the adaptation of vegetables, especially those susceptible to osmotic stress, is becoming more and more challenging to acquire sustainable cropping systems in saline environment. Unlike melon hybrids, melon landraces are less sensitive to environmental stresses and considered valuable sources of genetic characteristics for plant breeders' interest in breeding programs. This study was designed to assess the impact of salinity on several fruit quality characteristics of three melon landraces namely 'Tendra negro', 'Thrakiotiko' and 'Leyko Amyntaiou'. Both, the widely cultivated Spanish cultivar 'T111 (tipo piel de sapo)' and the commercial hybrid 'Lavigal' served as control. The experiment was carried out at the greenhouse facilities of the Laboratory of Vegetable Production at the Agricultural University of Athens. The different melon genotypes were hydroponically cultivated in an open hydroponic system with perlite as substrate, by applying a nutrient solution of 0.5 mM NaCl to the non-saline treated plants and 30 mM NaCl to the salt exposed plants. To investigate the impact of the salt stress on fruit quality, parameters such as the dry matter content, the pulp firmness, the values of color parameters L∗ a∗, b∗, hue angle and chroma and the titratable acidity were determined. The results showed that the color parameters and the pulp firmness were cultivar depended and were not affected by the salinity stress applied. Moreover, salinity stress resulted in increased dry matter content of the landrace 'Thrakiotiko', increased titratable acidity of the landrace 'Leyko Amyntaiou'. However, all tested parameters for the 'Tendra negro' landrace were not affected by the stress applied, indicating that this landrace could be a good candidate to be used in breeding programs for improving the tolerance of the commercial melon to salt stress

Impact of salinity stress on fruit quality of different Mediterranean cherry-type tomato landraces

Abiotic stresses, such as salinity, pose major risks on sustainability and productivity of most vegetable crops in the Mediterranean Basin. In soilless cultivation systems, mild salinity stress is introduced as a common practice to improve the organoleptic characteristics of tomato fruit, compromising at the same time crop production. In this study, we aimed to identify the impact of the salinity stress on the fruit quality of seven cherry-type tomato landraces (namely 'tomataki', 'GR-451/04', 'CC-1791 Allungato a Fiasco', 'Cherry-INRAE (1)', 'Cherry-INRAE (2)', 'Cherry-INRAE (3)', 'Cherry-INRAE (4)'). The experiment was conducted at the greenhouse facilities of the Laboratory of Vegetable Production at the Agricultural University of Athens. To apply the stress factor, the plants were grown under 30 mM NaCl in the nutrient solution versus the non-saline treated plants that were irrigated with a nutrient solution containing 0.5 mM NaCl. Fruit quality parameters such as diameter, firmness, titratable acidity (TA) and total soluble solids content (TSSC) were assessed. According to the main findings of this study, no reduction in the fruit quality characteristics of the landraces 'Cherry-INRAE (1)', 'Cherry-INRAE (2)' and 'Cherry-INRAE (3)' when exposed to salinity was observed. Salt stress improved the fruit firmness, TSSC and TA of the Greek landrace 'GR 451/04' while reduced its fruit diameter. On the contrary, increased salinity in the nutrient solution did not affect the diameter of fruit for landrace 'Cherry-INRAE-4', while led to increased concentrations of TSSC in fruit. The identified tolerant and resistant landraces could potentially be used in breeding programs to develop new cultivars and hybrids that can better adapt in saline-affected environments