Bahar Yildiz Kutman

Tomato crop residues (TCR) from soilless greenhouses are treated as waste, causing greenhouse gas emissions and biomass loss. Within a circular economy framework, gasification converts TCR into renewable energy and biochar; however, its high pH and electrical conductivity (EC) limit its use as a substrate. This study evaluated whether pre-treatment could enable TCR biochar to act as a substrate component and nutrient source in tomato and pepper seedlings. Biochar was produced by gasification and pre-treated by water incubation plus nitric acid, reducing EC from 27 to 8.7 dS m⁻¹ and pH from 10.4 to 8.2 while achieving nitrate loading without leaching. Pristine biochar severely restricted growth. Subsequent experiments evaluated pre-treated biochar mixed with perlite or cocopeat, with or without external N and K. The 15/85% (w/w) pre-treated biochar/cocopeat mixture (PTB/C) showed the best overall performance. In the absence of additional N/K, PTB/C produced shoot biomass and shoot N concentrations comparable to N-/K-supplemented cocopeat; shoot K was comparable in tomato and higher in pepper. With N and K supplementation, PTB/C exceeded supplemented cocopeat biomass by 1.41- and 1.95-fold in tomato and pepper, respectively. These results indicate that pre-treated TCR biochar can reduce dependence on imported cocopeat and external N/K supply.

The use of seaweed-derived biostimulants has gained attention as a sustainable strategy to enhance crop production. Brown seaweeds, in particular, are rich in bioactive compounds that can improve plant growth, yield, and quality parameters. This study investigated the biostimulant potential of extracts derived from Cystoseira barbata for promoting tomato growth and improving fruit quality. Three different extracts (water, alkali, and acid), applied as soil drenches, were tested on a determinate tomato cultivar under greenhouse conditions. In young plants, alkali and acid extracts increased stem length by 40% and 60%, respectively, while water and acid extracts accelerated early flowering. Alkali and acid extracts also improved fruit yield by approximately 65%. Additionally, all extracts enhanced fruit quality by increasing fruit EC and Brix values, soluble carbohydrate levels, total phenolic content, total antioxidant capacity, lycopene and β-carotene concentrations, and vitamin C content, albeit to varying degrees. Along with increases in fruit K concentration in response to water and alkali extracts, all seaweed extract-treated groups showed elevated fruit S concentrations, accompanied by increases in reduced glutathione levels. These results indicate that C. barbata extracts can enhance plant performance while improving the nutritional and nutraceutical properties of tomato fruits. The observed effects were strongly influenced by the extraction method, which alters the extract composition. Extracts from sustainably sourced C. barbata may contribute to improved productivity and quality in horticulture; however, further research is needed to enable the standardized production of C. barbata, optimize biostimulant formulations, and validate their effectiveness under field conditions.

Worldwide, where the demand for novel and greener solutions for sustainable agricultural production is increasing, the use of eco‐friendly products such as seaweed‐derived biostimulants as pre‐sowing treatment represent a promising and important approach for the future. Cystoseira barbata, a brown seaweed species abundant in the Mediterranean Region, was collected from the Marmara Sea and subjected to water, alkali, and acidic extractions, and the biostimulant activity of these extracts was tested on wheat (Triticum durum cv. Saricanak‐98) using different rates through application to the seeds or germination medium (substrate) applications. The different extracts were characterized by mineral, total phenolic, free amino acid, mannitol, polysaccharide, antioxidant concentrations and hormone‐like activity. The effects of the extracts on growth parameters, root morphology, esterase activity, and mineral nutrient concentrations of wheat seedlings were investigated. Our results suggest that the substrate application was more effective in enhancing the seedling performance compared to the seed treatment. High rates of seaweed extracts applied to substrates increased the shoot length and fresh weight of wheat seedlings by up to 20 and 25%, respectively. The substrate applications enhanced the root fresh weights of wheat seedlings by up to 25% when compared to control plants. Among the biostimulant extract applications, the water extract at the highest rate yielded the most promising results in terms of the measured parameters. Cystoseira barbata extracts with different compositions can be used as effective biostimulants to boost seedling growth. The local seaweed biomass affected by mucilage problems, has great potential as a bioeconomy resource and can contribute to sustainable practices for agriculture.

Editorial: Women in plant nutrition: 2022

While the importance of beneficial soil microorganisms for soil health and crop performance has been receiving ever-increasing attention, Serendipita indica has been widely studied as a fungal root endophyte with significant potential for increasing the stress tolerance of host plants. Boron (B) toxicity as an adverse soil condition is particularly prevalent in arid and semi-arid regions and threatens crop production. Studies on S. indica-wheat symbiosis are limited, and effects of S. indica on crops have never been reported in the context of B toxicity. Here, two pot experiments were conducted under greenhouse conditions to investigate the effects of S. indica on the growth and yield parameters of bread (Triticum aestivum) and durum wheat (Triticum durum) grown at different levels of B toxicity in native vs. sterilized soil, and parameters related to root colonization, membrane damage, oxidative stress, chlorophyll, and mineral nutrition were measured to elucidate the physiological mechanisms of damage and benefit. Boron toxicity decreased early vegetative growth and grain yield, but it did not affect the straw dry weight of mature plants, whereas S. indica significantly enhanced the vegetative growth, straw dry weight, and the grain number of both wheat species. Membrane damage as demonstrated by increased lipid peroxidation and relative electrolyte leakage was caused by B toxicity and alleviated by S. indica. The benefits provided by S. indica could not be attributed to any significant changes in tissue concentrations of B or other minerals such as phosphorus. Soil sterilization generally improved plant performance but it did not consistently strengthen or weaken the effects of S. indica. The presented results suggest that S. indica may be used as an effective microbial inoculant to enhance wheat growth under adverse soil conditions such as B toxicity through mechanisms that are possibly unrelated to mineral homeostasis.

Salinity negatively affects agricultural production by reducing crop growth and yield. Botanical biostimulants can be used as innovative and sustainable tools to cope with abiotic stress. In this study, salicylic acid (SA) (25 µM) and willow leaf (WL) (0.1 and 0.2%) and bark (WB) (0.1 and 0.2%) extracts were applied as plant-based biostimulants to hydroponically grown maize in the absence and presence of salinity stress (60 mM NaCl). The hormone-like activity and mineral composition of willow extracts were analyzed, and the effects of willow extracts on growth parameters, chlorophyll content, antioxidative enzyme activities, protein levels and mineral nutrient concentrations of maize plants were measured. Within the tested biostimulant applications, 0.2% WB, 0.1% WL and 0.2% WL gave the most promising results, considering the stress alleviating effects. The shoot biomass was increased up to 50% with 0.1% WL treatment and Na⁺ uptake was reduced with biostimulant applications under saline conditions. Under stress, the protein concentrations of maize leaves were enhanced by 50% and 80% with high doses of WB and WL applications, respectively. Results indicate that willow tree prunings can be valuable bio-economy resources, and aqueous extracts prepared from their leaves and barks can be used as effective and eco-friendly biostimulants.

Biostimulants can be used as innovative and promising agents to address current needs of sustainable agriculture. Weeping willow tree (Salix babylonica) extracts are rich in many bioactive compounds, including, but not limited, to salicylates and phenolics. In this study, the potential of willow bark (WB) and willow leaf (WL) extracts is evaluated as plant-based biostimulants to improve the early growth of maize (Zea mays) under control and salinity stress conditions. In 3 days, seed treatment with salicylic acid and willow extract increased the shoot FW of maize seedlings 130% and 225%, respectively. The root area was, on average, enhanced by 43% with SA and 87% with willow extract applications. Moreover, these extracts increased the leaf protein concentration and reduced the negative effects of salinity during early growth. Reductions in lipid peroxidation and specific activities of antioxidative enzymes by seed treatments with willow extracts suggests a mitigation of salinity-induced oxidative stress. For most reported traits, WL applications were at least as effective as WB applications. Results indicate that aqueous extracts of weeping willow leaves, as well as bark, can be used as seed treatment agents with biostimulant activity to improve seedling growth and establishment under control and stress conditions.

Glyphosate is an important component of herbicide programs in orchard crops in California. It can be applied alone or in tank-mix combinations under the crop rows or to the entire field and often is used multiple times each year. There has been speculation about the potential impacts of repeated use of glyphosate in perennial crop systems, because of uptake from shallow root systems or indirectly because of effects on nutrient availability in soil. To address these concerns, research was conducted from 2013 to 2020 on key orchard crops to evaluate tree response to glyphosate regimens. Almond, cherry, and prune were evaluated in separate experiments. In each crop, the experimental design was a factorial arrangement of two soil types, four glyphosate rates (0, 1.1, 2.2, and 4.4 kg ae ha⁻¹, applied three times annually), and two post-glyphosate application irrigation treatments. In the first 2 yr of the study, there was no clear impact of the glyphosate regimens on shikimate accumulation or leaf chlorophyll content, which suggested no direct effect on the crop. In the seventh year of the study, after six consecutive years of glyphosate application to the orchard floors, there were no negative impacts of glyphosate application on leaf nutrient concentration or on cumulative trunk growth in any of the three orchard crops. Lack of a negative growth impact even at the highest treatment rate, which included 18 applications of glyphosate totaling nearly 80 kg ae ha⁻¹ glyphosate over the course of the experiment suggest there is not likely a significant risk to tree health of judicious use of the herbicide in these production systems. Given the economic importance of orchard crops in California, and grower and industry concerns about pesticides generally and specifically about glyphosate, these findings are timely contributions to weed management concerns in perennial specialty crops.