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Background: To counteract soil degradation, it is important to convert conventional agricultural practices to environmentally sustainable management practices. To this end, the application of biostimulants could be considered a good strategy. Compost, produced by the composting of biodegradable organic compounds, is a source of natural biostimulants, such as humic acids, which are naturally occurring organic compounds that arise from the decomposition and transformation of organic residues, and compost tea, a compost-derived liquid formulated produced by compost water-phase extraction. This study aimed to determine the molecular responses of the roots of tomato plants (cv. Crovarese) grown under hydroponic conditions and subjected to biostimulation with humic substances (HSs) and filtered sterile compost tea (SCT)., Results: The 13 C CPMAS NMR of humic acids (HA) and SCT revealed strong O-alkyl-C signals, indicating a high content of polysaccharides.Thermochemolysis identified over 100 molecules, predominantly from lignin, fatty acids, and biopolymers. RNA-Seq analysis of tomato roots treated with HA or SCT revealed differentially expressed genes (DEGs) with distinct patterns of transcriptional reprogramming. Notably, HA treatment affected carbohydrate metabolism and secondary metabolism, particularly phenylpropanoids and flavonoids, while SCT had a broader impact on hormone and redox metabolism. Both biostimulants induced significant gene expression changes within 24 h, including a reduction in cell wall degradation activity and an increase in the expression of hemicellulose synthesis genes, suggesting that the treatments prompted proactive cell wall development., Conclusions: The results demonstrate that HS and SCT can mitigate stress by activating specific molecular mechanisms and modifying root metabolic pathways, particularly those involved in cell wall synthesis. However, gene regulation in response to these treatments is complex and influenced by various factors. These findings highlight the biostimulatory effects of HS and SCT, suggesting their potential application in crop biofertilization and the development of innovative breeding strategies to maximize the benefits of humic substances for crops. Further research is needed to fully elucidate these mechanisms across various contexts and plant species., (© 2024. The Author(s).)

Nowadays, modern agriculture looks for valid, sustainable, and green alternatives that are able to improve and maintain soil quality and fertility over time. Recycling organic waste as fertilizer is one of the strategies for sustainable production. Recently, the use of new products derived from compost, such as compost tea (CT), is increasing due to their positive effects on crops. This perspective wants to give an updated shot at the effect of compost tea in horticulture. In addition to the classification of compost tea, with a focus on production procedures and composition, the possible effects they have both on the control of phytopathogens in horticulture and the influence they can have on the content of bioactive molecules and nutrients were highlighted. It is interesting to note that compost teas can have an effect on the final content of micro and macronutrients, thus improving the nutritional qualities and also increasing the content of bioactive compounds that may play a role in maintaining and improving human health. The combined use of compost tea with other treatments is being explored as a promising and innovative direction. [ABSTRACT FROM AUTHOR]

By-products of the agri-food sector are increasingly employed in the production of new organic preparations, with biofertilizer and biostimulating functions, thus reducing the consumption of non-renewable resources and turning production chains towards circular economy and sustainability. Two composts were produced with solid digestate (85%) as a common component and different sources of recyclable materials (15%): vine pruning wood (compost A), or shells and skin of hazelnuts (compost B). The two composts were used in replacement of variable percentages of peat in nursery substrates, and their effects on various growth parameters assessed on micropropagated plants of two widely demanded species: raspberry (compost A) and hazelnut (compost B). Composts revealed microbiologically safe growth conditions, nutritional content suitable for agronomic purposes and levels of heavy metals in compliance with the European standards. The trials demonstrated the possibility for a partial replacement of peat (up to 20% in hazelnut and 40% in raspberry) in nursery conditions, without compromising, and in some cases improving, the vegetative growth and plants nutritional status. Nonetheless, the highly variable hazelnut growth responses highlighted that compost concentration should be fine-tuned on sensitive species to avoid negative effects. In the case of raspberry, the use of these substrates could also be experimented for soilless production. Because of the potential for metals accumulation, analysis on the extended applications should be made prior to considering field applications. [ABSTRACT FROM AUTHOR]

The aim of the present study was to characterize the physical-chemical and microbiological features of aerated compost teas (CTs) extracted with dechlorinated tap water and with two different additives, molasses and whey, in increasing doses. Plant pathogen suppression properties of CTs were also taken into account. Total nitrogen in CTs increased with rising doses of the additives used. In spite of this, nitrogen and mineral element contributions were limited but complementary for plant mineral nutrition. Although total heavy metal contents in CTs were low, an increase of their bioavailable forms (ionic and chelated forms, presence in microorganisms) should be taken into account. In addition, the distribution on soil of acid and/or chelating products by CTs could increase the bioavailability of heavy metals, especially in the case of several annual distribution cycles and of medium–long term treatments. Additives modulated the structure and composition of microbial communities and CTs, exhibiting a broad spectrum of suppressive properties against plant pathogens, especially when they were used in a raw form. [ABSTRACT FROM AUTHOR]

Municipal waste compost was evaluated under open field conditions for replacing synthetic fertilizers in a vegetable three-year succession. Three compost rates, 45 t ha-1, 30 t ha-1 and 15 t ha-1 (dry matter), and compost at 15 t ha-1 combined with 25%, and 50% of the full synthetic nitrogen rate, were compared to full and none synthetic nitrogen fertilizations. Crop succession was: tomato followed by endive in the first year; eggplant and, then, broccoli in the second year; tomato and, then, endive/broccoli, in the third year. The application of compost at a dose of at least 30 t ha-1 or at 15 t ha-1 with the addition of 25% of the full synthetic nitrogen rate, in Spring-Summer cycle, sustained growth and yield at levels comparable with those of synthetic nitrogen fertilization. However, only a very poor residual effect of the compost soil treatment on the yield of Autumn-Winter crops, was observed. Monitoring of nitrate content into the soil during cropping seasons, a reduction of the risk of groundwater pollution was displayed due to nitrates released by compost, respect to synthetic nitrogen fertilizer. The cumulative effects of compost application on soil properties were detected at the end of the field trials, registering changes in chemical parameters analysed, except for phosphorus and boron. [ABSTRACT FROM AUTHOR]

Cardoon (Cynara cardunculus L.) is considered as one of the most suitable energy crops for Southern Europe. The aim of this work was to outline the effects of organic fertilisers on the productivity and the global warming potential (GWP) on cardoon production. Six fertilisers (N 100 kg ha−1, N 50 kg ha−1, Compost 30 t ha−1, Compost 15 t ha−1 + N 25 kg ha−1, 3 t ha−1 of defatted oilseed meals of sunflower, 3 t ha−1 of defatted oilseed meals of Brassica carinata), and unfertilised control, were evaluated on two cultivars ('Gobbo di Nizza' and 'Altilis 41') in a split-plot experiment. Defatted oilseed meal of sunflower recorded higher total dry weight (+10%), seed yield (+17%), nitrogen use efficiency (+14%) and better GWP (−66%) compared to the other organic fertilisers and performing as well as N 100 kg ha−1. Altilis 41 cultivar showed the highest aboveground total dry weight (10 t ha−1 y−1), seed yield (1.7 t ha−1 y−1), stalk dry weight (7 t ha−1 y−1) and head dry weight (3 t ha−1 y−1). Our results highlighted that by combining suitable cultivar and fertilisation strategies, it could be possible to increase the production sustainability of C. cardunculus. [ABSTRACT FROM AUTHOR]

A stepwise screening strategy made it possible to identify five newBacillusspp. strains for biocontrol ofRhizoctonia solani,Sclerotinia minorandFusarium solani.In vitroandin vivobiocontrol activity and M13-PCR DNA-fingerprinting led to the selection of these valuable biological control agents (BCAs) from a wide collection of over 250 candidates. At the end of this selection, the highest potential antagonists were identified at species level by 16S-rRNA gene sequence analysis, and results assigned them toBacillus subtilisgroup asBacillus amyloliquefaciens-andBacillus methylotrophicus-related strains. In the current study, spore-forming bacteria provided substantial biocontrol of telluric diseases on cress and other different host plants. The strains named 15S and 09C were effective in disease control onBrassica oleracea/R. solanipathosystem, whereas Sclerotinia drop of lettuce was reduced by treatments with the strains 17S and 08C. Finally, the strains 17S and 12S were equally effective to control potato Fusarium rot. The evident zone of inhibition seen in dual culture plates suggested antibiosis-like antagonisms as the main mechanisms used by these bacterial isolates in interaction with the pathogens. Additionally, the API-ZYM method revealed constitutive activity of certain extracellular enzymes that could be involved in plant fortification.Bacillusstrains isolated from compost and compost-amended soils are promising BCAs that have potential for practical application as biofungicides. [ABSTRACT FROM AUTHOR]

• The study aims to recover aromatic plants residues of basil, rosemary and sage. • Essential oil, aromatic water and compost are new products from residue valorisation. • An eco-friendly flow model of recycling aromatic plant residues is proposed. • This model can be viable in other contexts in an optic of circular economy. In the last few years, the aromatic plant market for fresh consumption has been growing, especially packaged herbs for Mass Market Retailers. Pruning and selection of aromatic plants during packaging leads to the accumulation of a large amounts of plant residues with consequent disposal costs. In a circular economy perspective, the aim of this study was to recover residues of three aromatic plants (Ocimum basilicum L., Rosmarinus officinalis L. and Salvia officinalis L.) by extracting essential oil and aromatic water and, subsequently, reusing oil-free biomasses for composting. In fact, these by-products are currently considered very interesting and sustainable. The essential oils are natural products that have a wide range of biological activities useful for pharmaceutical, medical, veterinary and agriculture innovative purposes. Hydrolates have a much softer scent than the corresponding essential oils. The compost can be successfully applied for the restoration and maintenance of soil fertility. Results of this study showed that yields of essential oils obtained from plant residues, were sufficiently higher, especially for sage and rosemary, also if they were collected well far from plant balsamic period. Analysis of composition of essential oils confirmed the presence of characteristic compounds for each species. The aromatic waters were found to be an easily usable product due to the favourable physicochemical characteristics and, in particular, the aromatic waters of basil showed high antioxidant activity. About compost, the main physicochemical (humidity, pH, electrical conductivity) and biological (basal respiration and hydrolase activity) properties, were considered. Phytotoxicity tests indicated that composts derived from the three species can be used in agriculture. This research demonstrates that it is possible to eliminate completely plant residues and recover new products from aromatic species, supporting the effectiveness of an eco-friendly model to recover and reuse all fresh aromatic plant residues. [ABSTRACT FROM AUTHOR]

Compost teas (CTs) are liquid organic formulates obtained by prolonged extraction, with or without aeration, of a quality compost into an aqueous medium. They can significantly improve plant growth and development likely through nutritive and/or biostimulant mechanisms. In nursery production chain of tomato, pepper and melon, the use of seven CTs was evaluated in order to substitute, totally or partially, chemical treatments with propamocarb-hydrochloride (47.3%) and fosetyl-Al (27.7%), a fungicide for the pathogenic oomycetes control. In general, CTs increased plant growth parameters, as suggested by measurements of root length (+9.1% and +8.1%, on average, on tomato and pepper, respectively), stem diameter (+12% on average, on tomato), number of leaves (+2.6% on average, on melon), and fresh biomass (+8.2% on average, on melon) in comparison with the chemical control. CT from artichoke and fennel composted residues have had the major impact on nursery performances of tomato, pepper and melon. After the first treatment of the polystyrene trays with the fungicide at sowing, our results indicated that CT may replace it in the following seedling production cycle, securing vegetative characteristics of nursery plants similar to the chemical control, that may incite fast starting of transplants in the field stage. [ABSTRACT FROM AUTHOR]

Green waste composts are obtained from agricultural production chains; their suppressive properties are increasingly being developed as a promising biological control option in the management of soil-borne phytopathogens. The wide variety of microbes harbored in the compost ecological niches may regulate suppressive functions through not yet fully known underlying mechanisms. This study investigates alpha- and beta-diversity of the compost microbial communities, as indicators of the biological features. Our green composts displayed a differential pattern of suppressiveness over the two assayed pathosystems. Fungal and bacterial densities, as well as catabolic and enzyme functionalities did not correlate with the compost control efficacy on cress disease. Differences in the suppressive potential of composts can be better predicted by the variations in the community levels of physiological profiles indicating that functional alpha-diversity is more predictive than that which is calculated on terminal restriction fragments length polymorphisms (T-RFLPs) targeting the 16S rRNA gene. However, beta-diversity described by nMDS analysis of the Bray–Curtis dissimilarity allowed for separating compost samples into distinct functionally meaningful clusters and indicated that suppressiveness could be regulated by selected groups of microorganisms as major deterministic mechanisms. This study contributes to individuating new suitable characterization procedures applicable to the suppressive green compost chain. [ABSTRACT FROM AUTHOR]

While the control of soil-borne phytopathogenic fungi becomes increasingly difficult without using chemicals, concern over the intensive use of pesticides in agriculture is driving more environmentally sound crop protection managements. Among these approaches, the use of compost to suppress fungal diseases could have great potential. In this study, a multidisciplinary approach has been applied to characterize microbiota composition of two on-farm composts and assess their suppress and biostimulant activities. The on-farm composting system used in this study was able to produce two composts characterized by an antagonistic microbiota community able to suppress plant pathogens and biostimulate plant growth. Our results suggest a potential role for Nocardiopsis and Pseudomonas genera in suppression, while Flavobacterium and Streptomyces genera seem to be potentially involved in plant biostimulation. In conclusion, this study combines different techniques to characterize composts, giving a unique overview on the microbial communities and their role in suppressiveness, helping to unravel their complexity. [ABSTRACT FROM AUTHOR]

• Leafy vegetable/cardoon residues were composted by three different on-farm methods. • Compost suppressiveness was assessed against two soil-borne pathogens. • Microbial activity and diversity into compost is crucial for suppressiveness. • Biodegradable C sustained microbial disease suppression in actively aerated compost. • Linear and microbial fatty acids supported antagonisms in passive aerated compost. On-farm composting is suitable to recycle agricultural biomasses in mature and stable organic matter that can be applied to improve the general soil conditions, such as physical, chemical, hydro-physical, texture, and refresh the provided ecosystem services for human well-being. Quality compost have a high potential in sustaining plant health through disease suppressiveness mechanisms against soil-borne pathologies; however, this property needs to be standardized. In this work, leafy vegetable/chipped energy cardoon residues have used as common starting feedstock in three comparative composting piles differentiated for the aeration method (passive, active and manual turning). Compost from both passively and actively aerated static piles showed higher suppressive properties against Lepidium sativum damping-off caused by Rhizoctonia solani and Sclerotinia minor. The enhanced suppressiveness was found associated to increased population levels of fungi and bacteria, combined with larger microbial activity and catabolic diversity. Compost community levels of physiological profiles were distributed within PCA biplots according to the gradient of suppressiveness and, putatively, their C-food bioavailability degree. The observed differences in stimulation and selection of microbiota may be related to specific molecular compost features. The two suppressive compost revealed either a distinct lipid composition, assessed by thermochemolysis and to the preservation of readily biodegradable molecules by lignocellulosic components, as detected in NMR analyses. Findings indicate the relevance of on-farm composting methods in shaping compost suppressive functions and give new information about the provisioning of bio-based products for sustainable plant disease management. [ABSTRACT FROM AUTHOR]