In soilless cultivation, plants are grown with nutrient solutions prepared with mineral nutrients. Beneficial microorganisms are very important in plant nutrition. However, they are not present in soilless culture systems. In this study we investigated the impact of introducing Plant Growth Promoting Rhizobacteria (PGPR) as an alternative to traditional mineral fertilizer in hydroponic floating lettuce cultivation. By reducing mineral fertilizers at various ratios (20%, 40%, 60%, and 80%), and replacing them with PGPR, we observed remarkable improvements in multiple growth parameters. Applying PGPR led to significant enhancements in plant weight, leaf number, leaf area, leaf dry matter, chlorophyll content, yield, and nutrient uptake in soilles grown lettuce. Combining 80% mineral fertilizers with PGPR demonstrated a lettuce yield that did not significantly differ from the control treatment with 100% mineral fertilizers. Moreover, PGPR application improved the essential mineral concentrations and enhanced human nutritional quality, including higher levels of phenols, flavonoids, vitamin C, and total soluble solids. PGPR has potential as a sustainable substitute for synthetic mineral fertilizers in hydroponic floating lettuce cultivation, leading to environmentally friendly and nutritionally enriched farming.

Backround: The utilization of high-quality water in agriculture is increasingly constrained by climate change, affecting availability, quality, and distribution due to altered precipitation patterns, increased evaporation, extreme weather events, and rising salinity levels. Salinity significantly challenges salt-sensitive vegetables like lettuce, particularly in a greenhouse. Hydroponics water quality ensures nutrient solution stability, enhances nutrient uptake, prevents contamination, regulates pH and electrical conductivity, and maintains system components. This study aimed to mitigate salt-induced damage in lettuce grown via the floating culture method under 50 mM NaCl salinity by applying biostimulants. Results: We examined lettuce’s physiological, biochemical, and agronomical responses to salt stress after applying biostimulants such as amino acids, arbuscular mycorrhizal fungi, plant growth-promoting rhizobacteria (PGPR), fulvic acid, and chitosan. The experiment was conducted in a greenhouse with a randomized complete block design, and each treatment was replicated four times. Biostimulant applications alleviated salt’s detrimental effects on plant weight, height, leaf number, and leaf area. Yield increases under 50 mM NaCl were 75%, 51%, 31%, 34%, and 33% using vermicompost, PGPR, fulvic acid, amino acid, and chitosan, respectively. Biostimulants improved stomatal conductance (58–189%), chlorophyll content (4–10%), nutrient uptake (15–109%), and water status (9–107%). They also reduced MDA content by 26–42%. PGPR (1.0 ml L^‒1), vermicompost (2 ml L^‒1), and fulvic acid (40 mg L^‒1) were particularly effective, enhancing growth, yield, phenol, and mineral content while reducing nitrate levels under saline conditions. Conclusions: Biostimulants activated antioxidative defense systems, offering a sustainable, cost-effective solution for mitigating salt stress in hydroponic lettuce cultivation.

Hydroponics is one of the systems in agriculture which reinforce productivity by controlling environmental and growing conditions. In this study, we evaluated the effect of three bio-fertilizers, namely bacteria, micro-algae, and mycorrhiza, on basil leaf yield and quality (Ocimum basilicum L.) in a floating culture system. Soil has rich amounts of beneficial microorganisms, supporting plant nutrition, producing phytohormones, controlling phytopathogens, and improving soil structure. However, soilless culture usually contains no beneficial microorganisms if we do not include them in the system. This study aims to evaluate the response of three bio-fertilizers where mineral fertilizers are reduced by 50%. Considering the total harvest data, bacteria, mycorrhiza, and micro-algae treatments increased basil yield compared to 50% control by about 18.94%, 13.94%, and 5.72%, respectively. The maximum total yield and leaf area were recorded using bacteria with 2744 g m⁻² and 1528 cm² plant⁻¹. Plants with mycorrhiza achieved the highest number of leaves and branches, with 94.3 leaves plant⁻¹ and 24.50 branches plant⁻¹, respectively. It was observed that this bio-fertilizer increased the formation of lateral branches in the basil plant without thickening its stems. In addition, bacteria and mycorrhiza induced the highest percentage of dry matter and total soluble solids. The effect of bio-fertilizers on basil leaf EC and pH was insignificant for all the treatments at different harvest periods (p < 0.05). Using bio-fertilizers enhanced the intake of nutrients N (nitrogen), P (phosphorus), K (potassium), Ca (calcium), Mg (magnesium), Fe (iron), Mn (manganese), Zn (zinc), and Cu (copper). Using bio-fertilizers represents a promising and environmentally friendly approach to increasing crop yields and ameliorating quality and antioxidant compounds with fewer resources. An application of bio-fertilizers in hydroponic cultivation of basil cv. ‘Dino’ reduced the need for mineral fertilizers. At the same time, bio-fertilizers affected an increased plant yield and improved product quality. Furthermore, the bacteria had a pronounced enhancing effect on the increase of phenol and flavonoids in the leaves of basil plants.

Plant nutrition through mineral fertilizers is commonly used in soilless culture systems. Our study aims to replace intensive mineral fertilizers with bio-fertilizers, at least partially. We supplemented 50% of the mineral fertilizers with Chlorella vulgaris microalgae, a mix of beneficial bacteria and mycorrhiza. In addition, we investigated how to enhance spinach quality by implementing a sustainable and eco-friendly production method. Our research focused on analyzing the parameters of leaf quality and nitrate accumulation of baby spinach grown in a floating culture system utilizing biofertilizers. When mycorrhiza, algae, and bacteria supplemented 50% of mineral fertilizers, 17.5%, 20%, and 21.9% fewer leaf yields than 100% mineral fertilizers (5270 g m⁻²) were achieved. However, biofertilizers improved the internal leaves’ quality of hydroponically grown baby spinach. The highest amount of total phenolic (356.88 mg gallic acid 100g⁻¹), vitamin C (73.83 mg 100 g⁻¹), total soluble solids (9.4%), phosphorus (0.68%), and iron (120.07 ppm) content were obtained by using mycorrhiza. Bacteria induced the lowest nitrate content (206 mg kg⁻¹) in spinach leaves, while 100% mineral fertilizers showed the highest nitrate (623 mg kg⁻¹) concentration. Moreover, bacteria provided the highest SPAD-chlorophyll (73.72) and titrable acidity (0.31%). The use of microalgae, Chlorella vulgaris, induced the highest amount of potassium (9.62%), calcium (1.64%), magnesium (0.58%), zinc (75.21 ppm), and manganese (64.33 mg kg⁻¹). In conclusion, our findings demonstrate that the utilization of biofertilizers has the potential to significantly reduce the reliance on mineral fertilizers by up to 50%. Furthermore, an improvement in the quality of baby spinach, as evidenced by an increase in health-beneficial compounds, is possible. Thus, implementing biofertilizers in the cultivation of soilless baby spinach presents a promising approach to achieving both environmental sustainability and improved crop quality.

Globally, one in every four individuals faces a deficiency in essential micronutrients. Harvested early from various vegetables, grains, and herbs, microgreens have rich nutritional profiles that can mitigate nutrient deficiencies. Here, we analyzed six microgreens’ nutritional profiles for broccoli, black radish, red beet, pea, sunflower, and bean. Ascorbic acid content varied widely, from 32.72 mg/100 g fresh weight (FW) in red beet to 80.45 mg/100 g FW in beans. All microgreens exhibited high macro elements (mg/100 g FW), with potassium ranging from 187.07 to 416.05, magnesium from 45.96 to 86.83, calcium from 67.18 to 148.63, and phosphorus from 2.57 to 4.88. They also contained significant microelements (µg/100 g FW), including iron from 524 to 2610, manganese from 176.32 to 350.56, zinc from 31.92 to 129.78, and copper from 458.84 to 956.34. Glucose content surpassed sucrose and fructose, ranging from 0.114 to 0.580 mg/100 g FW. Among organic acids, citric acid was highest in red beet, succinic acid in beans, and fumaric acid in sunflower. Broccoli microgreens had the highest total phenolic content (825.53 mg GA/100 g FW), while beans had the highest total flavonoid content (758.0 mg RU/100 g FW). Black radish microgreens demonstrated the highest antioxidant capacity. Additionally, volatile aromatic compounds were analyzed across the six microgreen species. These findings highlight the nutritional potential of microgreens, advocating for their inclusion in diets to enhance human health. Red beet microgreens were the richest in organic acids, particularly citric acid, and flavonoids, supporting antioxidant activity, while black radish microgreens exhibited the highest DPPH antioxidant capacity and phenolic content. Bean microgreens stood out for their high ascorbic acid content. Sunflower microgreens had the highest levels of calcium and fumaric acid. Broccoli microgreens were abundant in phenolic compounds and contained high concentrations of iron and manganese. Finally, pea microgreens excelled in phosphorus and copper content.