Peat has long been the primary substrate for the production of ornamental and horticultural plants in pots. Today, peat is no longer considered a renewable resource due to its very lengthy regeneration time. Biochar, a solid by-product of biomass pyrolysis, has been proposed as an agricultural soil amendment. We investigated the effects of two types of biochar, namely biochar from pruning wood waste and biochar activated with wood vinegar (“smoked biochar”), on two ornamental plants (Lavandula angustifolia and Salvia rosmarinus) and on strawberries (Fragaria × ananassa). For both types of biochar, we measured the following parameters: the pH, density, electrical conductivity, humidity, calcium carbonate, total carbon, nitrogen, potassium, calcium, magnesium, sodium, and water retention. For peat, we measured the following parameters: the pH, electrical conductivity, total carbon, and total nitrogen. Our results showed an overall increase in plant growth, particularly in L. angustifolia when using 10% and 50% biochar concentrations and a 10% concentration of biochar activated with wood vinegar. In S. rosmarinus, we observed a slight increase in the total plant weight with the application of 10% smoked biochar (biochar activated with wood vinegar). Finally, in F. × ananassa, we observed an increase in the plant weight and fruit production when 10% biochar was applied. On the other hand, when high concentrations of biochar (50% and 100%) and especially smoked biochar were applied, we observed a significant reduction in the growth of all plants. We concluded that biochar and biochar activated with wood vinegar showed remarkable biological activity with marked phytotoxicity at high concentrations. They promoted plant growth when applied diluted and their use as partial peat substitutes could help support more sustainable horticultural practices.

Downy mildew, caused by Plasmopara viticola, is a major threat to grapevine (Vitis vinifera) cultivation in humid climates. Restrictions on synthetic pesticides and inconsistent efficacy of current biocontrol agents, especially under rainy conditions, complicate disease management. This study evaluated the potential of compost tea to suppress downy mildew in a two-year field experiment (2023 and 2024), combined with reduced synthetic fungicide applications. The study design compared two phytosanitary management strategies on a commercial vineyard: a conventional fungicide against a compost tea strategy supplemented with two cymoxanil applications. The experiment set up had three replicated blocks, each consisting of 100 plants for a total of 600 plants. Mechanistic insights were provided through controlled laboratory experiments involving pre- and post-infection leaf assays, vineyard bacteriome profiling, via 16S rRNA gene sequencing for bacterial communities, across vineyard compartments, i.e., bulk soil, rhizosphere, and phyllosphere, and grapevine metabolomic analysis by GC-MS analysis. Field trials demonstrated that compost tea combined with two fungicide applications effectively reduced disease severity, notably outperforming the fungicide alone in the particularly rainy year of 2023. Bacteriome analysis revealed that compost tea treatment enriched beneficial bacterial genera, including Pseudomonas, Sphingomonas, Enterobacter, Massilia, and Bacillus, known for their growth-promoting and biocontrol activity in the rhizosphere and phyllosphere. Laboratory assays on detached leaves further showed that compost tea alone could suppress both infection and sporulation of P. viticola. Metabolomic analysis highlighted the accumulation of compounds such as tartaric and shikimic acids in compost tea treated leaves, suggesting a potential role in induced resistance. The findings indicate that applying compost tea with reduced fungicide treatments represents a promising and sustainable strategy for managing grapevine downy mildew, even in challenging climates.

The development of sustainable seed coating formulations is essential to enhance crop performance while reducing reliance on synthetic inputs. This study evaluates biochar-enriched coatings incorporating olive pomace, buffalo digestate, and microbial consortia from Fagus, Quercus, and Pinus forest litters, including Trichoderma harzianum, for their effects on seed germination and plant growth. Four crops (Diplotaxis tenuifolia, Lactuca sativa, Solanum lycopersicum, and Zea mays) were tested through germination assays and field trials. Treatments containing digestate or pomace alone significantly reduced germination and seedling growth in D. tenuifolia and L. sativa (below 25%, compared to control), due to the phytotoxic effects of ammonia, salts, and polyphenols. In contrast, biochar-based coatings mitigated these effects, enhancing germination and root elongation. The addition of T. harzianum further improved seedling establishment, likely by enhancing nutrient uptake and suppressing soilborne pathogens, with increases exceeding 100% (compared to control). Field trials confirmed these findings, showing that biochar–T. harzianum combinations improved both shoot and root biomass, particularly in L. sativa and S. lycopersicum. Z. mays displayed greater tolerance to raw by-products, though biochar remained essential for optimal growth. While forest-derived microbial consortia supported microbial balance, their effect on biomass was less pronounced. These results highlight the potential of biochar-based coatings, especially when combined with T. harzianum, as sustainable alternatives to conventional seed treatments.

Posidonia oceanica, a Mediterranean Sea seagrass, generates significant litter debris in coastal regions, adversely affecting tourism. To manage this debris, we explored two strategies: (i) promoting in situ decomposition by introducing ligninolytic microbes from forest microbiomes and (ii) utilizing P. oceanica debris as a substrate for ornamental and horticultural species. To achieve this goal, we conducted a one-year experiment using litter bags in mesocosms that simulate in situ conditions, evaluating the second strategy with different application rates (10%, 30%, 50%, and 100%) of fresh and decomposed P. oceanica debris mixed with peat or soil, with or without mineral fertilizer. The results revealed the resistance of P. oceanica necromass to decomposition; in fact, the introduction of forest microbiomes led to a major decomposition rate, albeit with constrained practical applicability. Utilizing P. oceanica debris as a substrate without fertilizer resulted in a modest growth response relative to the application rate, particularly accentuated in horticultural species compared to ornamental ones. Mineral fertilizer alleviated adverse effects at lower application rates; however, a notable decline in growth was observed at the 100% application rate. At application rates of 10% and 30%, certain crops demonstrated improved growth compared to the control. In summary, our study suggests the potential use of raw P. oceanica debris as a growth substrate within the 10% to 50% dosage range.

Weed infestations are a major agricultural problem, driving the need for sustainable control methods beyond conventional synthetic herbicides. This study explored wood vinegar (WV), a pyrolysis by-product, as a dual-purpose tool for weed management and crop growth. Chemically characterized WV exhibited an acidic pH, high acetic acid content, and diverse organic compounds. Pot experiments demonstrated WV’s strong, concentration-dependent inhibition of weed seedling emergence. Field trials across three seasons confirmed WV’s efficacy in reducing weed density and biomass, particularly at 50% and 100% concentrations, while also influencing weed community composition. Critically, subsequent evaluation of residual phytotoxicity on tomato and courgette crops revealed that WV 50% significantly optimized both plant biomass and fruit yield. In contrast, WV 100% negatively impacted courgette yield, and WV 10% showed variable effects. These findings highlight WV, especially at optimal dilutions like 50%, as a promising sustainable solution for integrated weed management with potential biostimulant properties for crops.