Alkaline soil inhibits the growth and productivity of chia plants (Salvia hispanica L.). Microalgae as biofertilizers have been reported to induce alkalinity tolerance and enhance yield and quality. However, limited information is known concerning the influence of microalgae application on medical plants, including chia. Our experiments were performed to evaluate the effect of microalgae strains of Arthrospira platensis, Chlorella vulgaris, Nostoc muscorum, and Anabaena azollae with two application methods, foliar spray and soil drench, on morpho-physiological and biochemical parameters, yield, seed and oil quality, and fatty acid profiles of chia plants cultivated under alkaline soil conditions, as well as the on soil microbial activity. The results obtained reveal that both application methods positively influenced the growth and productivity of chia plants. However, the foliar application showed significant differences in the herb’s fresh and dry weights and leaf pigments, whereas the drenching application caused more effect than the foliar spray application at the reproductive stage. Untreated chia plants showed a slight decline in the growth, productivity, and antioxidant level with an increase in Na content. However, microalgae applications significantly ameliorated these impacts as they induced an enhancement in the growth, leaf pigments, total protein and carbohydrate contents, nutrient content, seed and oil yields, as well as an increase in linolenic and linoleic fatty acids, with a reduction in saturated fatty acids, namely, palmitic and lauric acid. Soil drenching generated an improvement in the soil microbial activity and caused a reduction in the pH. The treatment of A. platensis with drenching application resulted in higher seed and oil yield, with an increase of 124 and 263.3% in seed and oil yield, respectively.

Calcareous soil had sufficient phosphorus and potassium (PK) in different forms due to the high contents of PK-bearing minerals; however, the available PK state was reduced due to its PK-fixation capacity. Compost, coupled with high PK solubilization capacity microbes, is a sustainable solution for bioorganic fertilization of plants grown in calcareous soil. A 2-year field experiment was conducted to investigate the effect of compost (20 t ha⁻¹) with Aspergillus niger through soil drenching (C-AN) along with partial substitution of PK fertilization on quinoa performance in normal and calcareous soils. Treatments included PK_100% (72 kg P₂O₅ ha⁻¹ + 60 kg K₂O ha⁻¹ as conventional rate), PK_100%+C-AN, PK_75%+C-AN, PK_50%+C-AN, PK_25%+C-AN, and only C-AN in normal and calcareous soils. Results showed that C-AN and reduced PK fertilization (up to 75 or 50%) increased photosynthetic pigments and promoted nutrient acquisition in quinoa grown in calcareous soil. Reduced PK fertilization to 75 or 50% plus C-AN in calcareous soil increased osmoprotectants, nonenzymatic antioxidants, and DPPH scavenging activity of quinoa’s leaves compared to the PK_0%+C-AN treatment. The integrative application of high PK levels and C-AN enhanced the quinoa’s seed nutritional quality (i.e., lipids, carbohydrates, mineral contents, total phenolics, total flavonoids, half maximal inhibitory concentration, and antiradical power) in calcareous soil. At reduced PK fertilization (up to 75 or 50%), application of compost with Aspergillus niger through soil drenching increased plant dry weight by 38.7 or 53.2%, hectoliter weight by 3.0 or 2.4%, seed yield by 49.1 or 39.5%, and biological yield by 43.4 or 33.6%, respectively, compared to PK_0%+C-AN in calcareous soil. The highest P-solubilizing microorganism’s population was found at PK_0%+C-AN in calcareous soil, while the highest Azotobacter sp. population was observed under high PK levels + C-AN in normal soil. Our study recommends that compost with Aspergillus niger as a bioorganic fertilization treatment can partially substitute PK fertilization and boost quinoa’s tolerance to salt calcareous-affected soil.

Alkaline soils have fertility issues due to poor physical qualities, which have a negative impact on crop growth and output. Solidago is used in flower arrangements, bouquet filler, and traditional medicine. The possible biological fertilizers’ eco-friendly and cost-effective nature favours farmers because of the vital role in soil productivity and environmental sustainability. A field experiment was performed during two successive seasons to explore the effect of applying yeast extract (YE) at (0, 0.5, 1.0, and 1.5 g/L) and/or gibberellic acid (GA₃) at (control, 100, 200, and 300 ppm) on the morpho-physiological parameters, macronutrients, and biochemical constituents of Solidago virgaurea. The results emphasize that YE (1.5 g/L) and/or GA₃ (300 ppm) treatments show the highest significant increase in plant growth (i.e., plant height, no. of branches, fresh and dry weight of shoots); photosynthetic efficiency (i.e., chlorophyll (a), chlorophyll (b) and total carotenoids); macronutrient content (i.e., N, P, and K); and biochemical constituents (i.e., total soluble sugars, total phenolic, total flavonoids, and total glycosides). The study results recommend using YE and GA₃ in combination at concentrations of 1.5 g/L and 300 ppm, respectively, to improve Solidago production sustainability under alkaline soil conditions.

Salinity is one of several climate change impacts. Salinity in the water and soil has a negative effect on the growth and productivity of horticultural crops. Arginine has surfaced as a non-toxic plant growth governor that augments the resistance of plants to salt stress. Our objective was to assess the effects of exogenous foliar application of arginine on growth, yield, osmoprotectants and biochemical traits, as well as an antioxidant system of NaCl salt-stressed pot marigold plants. Two successive (2020/2021-2021/2022) pot trials were conducted using four NaCl salt concentrations (50, 100, 150 mM, plus control; non-NaCl salt) combined with three arginine levels (3, 6 mM, plus control; non-arginine sprayed plants). Higher NaCl salinity concentration showed a significant decrease in plant growth, yield, leaf total chlorophylls, and nutritional status, while exhibiting a substantial increase in Na+, Cl-, osmoprotectants and biochemical constituents, in addition to antioxidant activity. Exposing plants to 150 mM of NaCl salt decreased herb dry weight by 34.7%, No. of inflorescences by 30.4%, but increased Na content by 200.7%, Cl by 36.7%, and proline by 216.3% compared to control. Nevertheless, the foliar arginine application enhanced growth, yield, and antioxidant activity. Higher arginine treatment (6 mM) increased flower contents of total carotenoids by 3.67%, phenolics by 8.77%, flavonoids by 11.8%, DPPH by 5.25%, and 13.6% accumulation of free amino acids in leaves compared to untreated plants. Finally, exogenous arginine treatment had a mighty potential to encounter the effects of NaCl salt stress on pot marigold plants.

Syzygium cumini (L.) Skeels (jamun) is an ornamental tree species that is sensitive to salinity. Salinity stress is a major challenge, particularly in regions with saline irrigation water. In the present study, the ameliorative potential of foliar application of an aqueous extract of Delonix regia (Poinciana) flowers (PFE) to saline water-irrigated jamun seedlings was investigated over a period of two years. PFE was effective in mitigating the harmful effects of salinity on plant growth, physiology, and biochemistry. Salinity-induced reductions in plant height, leaf area, and biomass which were significantly alleviated by PFE foliar application. The extract also enhanced antioxidant activity, as indicated by increased ferric reducing antioxidant potential (FRAP) and phenolic content, while also reducing hydrogen peroxide (H₂O₂) levels and membrane damage as indicated by the accumulation of malondialdehyde (MDA). Additionally, the foliar application of PFE promoted the accumulation of free proline, an essential osmo-protectant, further enhancing the plant’s resilience to salinity stress. These findings highlight the potential of PFE as an eco-friendly bio-stimulant to improve salinity tolerance in jamun and pave the way for sustainable salinity management strategies in other crops as well.