Environmental stresses, particularly drought and salinity, significantly impair plant growth and productivity. This study explores the novel synergistic interaction between biochar and arbuscular mycorrhizal fungi (AMF) in enhancing the resilience of sweet pepper plants subjected to the individual or combined stresses of drought and salinity. The impact of these biostimulants on growth parameters, photosynthetic efficiency, and biochemical traits was assessed. Sweet pepper plants were subjected to drought stress (35 and 75% of field capacity (FC)), salinity (0 and 150 mM NaCl), and their combined effects (150 mM NaCl +35% of FC), with treatments including biochar (2.5 g/kg soil), AMF, and their combination. Under drought stress, the dual application of biochar and AMF notably improved plant growth indicators such as shoot fresh weight, shoot height, and number of leaves by 50, 14, and 3%, respectively compared to the control plants. Under drought and salinity combined, this combination also enhanced photosynthetic pigments content by 144% for Chl a, 316% for Chl b, 212% for Chl T and 302% for carotenoids content respectively compared to the control plants. Additionally, AMF and Biochar combined reduced the oxidative effect of malondialdehyde (MDA) by 37% and hydrogen peroxide (H2O2) by 43%, indicating a reduction in oxidative damage. Furthermore, a significant increase in antioxidant enzyme activities was observed, with peroxidase activity (POX) rising by 33% and polyphenol oxidase activity (PPO) increasing by 212%, indicating enhanced stress tolerance. This study underscores the efficacy of using biochar and AMF together to bolster sweet pepper plant resilience, offering a viable strategy for improving plant performance under challenging environmental conditions.

The increasing soil pollution has accelerated the implementation of new agricultural regulations that significantly limit the use of synthetic nitrogen (N) fertilizers. Consequently, plants are likely to experience nutrient stress, leading to decreased productivity and potential threats to food security. To address these critical challenges, microbial-based biostimulant (BS) products, which utilize metabolites from microorganisms, offer a sustainable and eco-friendly solution to mitigate plant nutrient stress. This study evaluated the effects of the radicular application of a microbial-based BS containing L-alpha-amino acids on lettuce and pepper crops under two nitrogen regimes: optimal N availability and N stress (NS). Various parameters, including growth, production, soluble proteins, photosynthetic pigment content, and oxidative stress markers, were assessed. Under optimal N conditions, BS application enhanced commercial biomass in lettuce and vegetative biomass in pepper, indicating that BSs can reduce the need for nitrate uptake and endogenous amino acid synthesis, thereby conserving energy for other physiological processes. Despite BS application, NS conditions significantly reduced vegetative and reproductive growth in both species. However, BS treatment in pepper plants increased chloroplast pigments, improving light absorption and photosynthetic efficiency. The reduction in the carotenoid/chlorophyll ratio suggests efficient N allocation to growth and production. Thus, BS application proved effective in mitigating NS in pepper plants, enhancing pepper production, while under optimal conditions, it improved lettuce yield, particularly commercial biomass. These findings underscore the potential of symbiotic microbial-based BSs as a promising tool for sustainable agriculture under reduced N availability.

Substituting peat moss with compost derived from organic waste in plant nurseries presents a promising solution for reducing environmental impact, improving waste management, and enhancing soil health while promoting sustainable agricultural practices. However, selecting the appropriate proportions of both materials is crucial for each plant species. This study investigates the effects of different ratios of compost and peat mixtures on the growth and development of pepper seedlings. The compost mixtures used in the study included the following combinations: sewage sludge with sawdust (A), sewage sludge with sawdust and biodegradable garden/park waste (B), and biodegradable garden/park waste with sawdust (C). The final substrates used for seedling production were composed of composts (A, B, C) and peat (O) as a structural additive, mixed in different proportions by mass: I-O 25%, II-O 50%, and III-O 75%. Seedlings grown in these substrates were assessed using biometric and physiological measurements. Nematode species present in substrates were identified by metabarcoding analysis. The results revealed that substrate productivity depended not only on nutrient content but also on structural properties, which were significantly influenced by the peat proportion. Among the tested compost mixtures, variant A I emerged as the most effective substrate, promoting optimal seedling growth. Molecular nematode analysis revealed significant nematode contamination in substrates with higher peat proportions (C II and C III), including Meloidogyne sp. Lichtenburg (26%), Meloidogyne hispanica (5%), Meloidogyne sp. Mi_c1 (3%), Meloidogyne ethiopica (2%), and Meloidogyne thailandica (1%). The findings underscore the critical importance of achieving an optimal balance between nutrient content and structural properties in substrates to support the healthy growth and development of pepper seedlings. To further enhance crop performance and reduce the risk of pest-related damage, it is essential to prioritize the improvement of substrate selection strategies. Monitoring for nematode contamination is crucial to prevent potential compromises in seedling quality and overall productivity.

Abiotic stresses, such as salt and drought, limit plant growth, reduce crop production, and pose the greatest challenge to the sustainability of agricultural development in arid and semi-arid countries. Arbuscular mycorrhizal fungi (AMF) and calcium can play an important role in alleviating the adverse effects of abiotic stresses on plants. Therefore, this study was conducted to evaluate the effect of two levels of mycorrhizal inoculation (inoculated seedlings and non-inoculated seedlings) and three levels of foliar spraying with calcium (0, 0.5%, and 1%), separately or in combination, on growth, physiology, and yield of salt-stressed pepper (Capsicum annuum L.). The experiment was conducted in an open field with saline soil and irrigation water, in a randomized complete block design with split plot arrangement. Mycorrhizal inoculation and calcium spray have been shown to facilitate nutrient uptake, modulate physiological responses, and activate the antioxidant system, enhancing salt stress tolerance and improving the growth and yield of salt-stressed pepper. Combined treatment plants grown from inoculated seedlings and sprayed with 1% Ca recorded the best results, alleviating salt stress-induced oxidative damage by activating the antioxidant system including antioxidant enzymes [Superoxide dismutase (SOD) and catalase (CAT)], and non-enzymatic antioxidants (ascorbic acid and phenols), reducing H2O2 and malondialdehyde (MDA) accumulation, enhancing physiological activities (relative water content (RWC %) and chlorophyll content), and improving nutrient balance (increasing N, P, K and reducing Na content), leading to increased pepper growth and yield parameters. Our results indicated that mycorrhizal inoculation and calcium spray can be recommended as a practical alternative and environmentally friendly approach to enhance plant tolerance to salt stress by improving nutritional status, physiological processes, and antioxidant activities, thus increasing the morphological and yield traits of stressed plants.