Search Results (31)

The large-scale use of compost in arable cropping systems is often limited by the large quantities required to meet the crop’s nutritional needs. Palletization can increase the nutrient density of organic fertilizers and improve their logistical feasibility by reducing storage, transport and application costs. This study evaluated the agronomic and environmental performance of compost pellets derived from pig slurry solids and olive pomace, using them as an alternative nitrogen source for wheat (Triticum aestivum L.) cultivated under Mediterranean conditions. A field experiment was conducted during the 2022–2023 growing season, with four treatments arranged in 24 m² replicated plots: an unfertilized control (C); pelletized compost (PSCOP); fresh pig slurry (PS); and mineral fertilization based on monoammonium phosphate and urea (IN). Excluding the control treatment, all fertilized plots received a uniform nitrogen rate of 150 kg N ha⁻¹. Soil chemical properties and nutrient availability (Pext, NH₄⁺-N and NO₃⁻-N) were evaluated at the beginning and end of the experiment, while wheat yield and grain quality were assessed at harvest. Greenhouse gas (GHG) emissions were monitored throughout the cropping season to evaluate environmental impacts. The results showed that the wheat yields achieved with PSCOP were comparable to those obtained with PS, although they remained lower than those achieved with mineral fertilization. Grain quality was not adversely affected by the application of PSCOP. Furthermore, PSCOP resulted in lower GHG emissions than mineral fertilization, with values closer to those observed in the unfertilized control. These findings suggest that pelletized organic fertilizers such as PSCOP may be a promising way to enhance nutrient circularity and reduce reliance on synthetic fertilizers and maintain crop productivity and limit environmental impact in Mediterranean agricultural systems. Full article

The growing demand for sustainable fertilization practices has stimulated interest in circular fertilizers derived from agro-industrial and agricultural wastes. This study assessed the agronomic and biological performance of several waste-based fertilizers—produced through composting, vermicomposting, and sulfur–bentonite enrichment—on chemical and microbiological soil properties. Composts and vermicomposts were prepared from olive pomace, citrus residues, wood sawdust, and straw, with or without elemental sulfur obtained from petroleum gas desulfurization. Field trials were conducted on a sandy loam soil (Motta San Giovanni, Italy) to compare the different formulations. After six months, soils amended with waste-based fertilizers exhibited significant improvements in key parameters relative to both the control and mineral fertilizer treatment. Vermicompost applications (SV1, SV2) increased total organic carbon by 20–30% (up to 2.1%), total nitrogen by 35–45% (0.22–0.23%), microbial biomass carbon by ~25% (≈1090 µg C g⁻¹), and dehydrogenase and fluorescein diacetate activities by 10–20% compared with compost or sulfur–bentonite treatments. Compost amendments (SC1, SC2) raised soil pH (8.2–8.3) and organic matter content (≈3.3–3.6%), while sulfur–bentonite formulations lowered pH to 7.1–7.3 and increased water-soluble phenols (up to 40 µg TAE g⁻¹ d.s). The highest cation exchange capacity (22–23 cmol (+) kg⁻¹) was observed in vermicompost-amended soils. Microbial community analysis revealed greater fungal abundance under sulfur–bentonite treatments, whereas bacteria and actinomycetes predominated in compost-amended soils. Principal Component Analysis (explaining 76% of variance) identified two main functional pathways: vermicompost treatments clustered with indicators of high biological activity (TOC, TN, MBC, and enzyme activities), while compost and sulfur–bentonite treatments were associated with pH, phenolic compounds, and fungal biomass, reflecting slower but more stable organic matter turnover. Overall, vermicompost-based fertilizers proved most effective in enhancing short-term nutrient availability and microbial activation, whereas composts favored long-term soil carbon accumulation and stability. These results highlight the potential of circular fertilizers derived from agro-industrial wastes to restore soil health, close nutrient cycles, and reduce dependence on synthetic fertilizers—thereby advancing sustainable and circular agriculture. Full article

Waste valorisation has become a key strategy for applying circular economy principles in the agro-industrial field. This study investigated the territorial implementation of the waste composting on a territorial scale. The wastes considered were the post-processing orange waste, spent olive oil pomace, and spent wine grape pomace. Their potential use as soil amendments across the provinces of Sicily was assessed through a GIS-based analysis, taking into account nitrogen (N) application constraints. Moreover, a cascade valorisation scheme was also evaluated: post-processing orange waste was first used as animal feed, and the remaining fraction was directed to composting; olive pomace was first sent to pomace oil extraction mills, and the residual material was subsequently used for composting. Results indicate that N inputs derived from composted residues remain below legal thresholds in all provinces, with relative contributions ranging from 38% to 92% of the regulatory limits. Spatial variability in nitrogen availability reflects the territorial distribution of agro-industrial activities, highlighting the importance of localised management strategies. These findings demonstrate that composting, combined with cascade valorisation, is an effective pathway to close nutrient cycles, reduce waste generation, and support sustainable biomass management in regional agri-food systems. Full article

The increasing demand for sustainable substrates in agriculture and urban greening calls for alternatives to peat, whose extraction poses significant environmental risks. This study assesses the potential of olive pomace biochar (OB), wood biochar (WB), and green compost (GC), alone or in combination, to partially replace peat in growing media and improve substrate properties and plant development. Ten different substrates were formulated by substituting 10–20% of a commercial peat-based substrate with these organic amendments, using the commercial substrate alone as a control. The effects of such replacements were evaluated in the following experiments: a germination test conducted in Petri dishes using four forage species (Medicago polymorpha, Lolium perenne, Festuca arundinacea, and Lolium rigidum); and two parallel pot experiments lasting 100 days each (one with M. polymorpha and L. perenne, and another with young Olea Europaea var. Arbequina saplings). This study evaluated the impact on plant development, as well as the physical properties and composition of the substrates during the incubation process. Germination and survival of forage species were comparable or improved in most treatments, except those including 20% OB, which consistently reduced germination—likely due to high electrical conductivity (>10dS/m). In the pot experiments, substrate pH and total carbon content increased significantly with biochar addition, particularly with 20% WB, which doubled total C relative to control. Both forage species (Medicago polymorpha and Lolium perenne) and the olive saplings (Olea Europaea) exhibited normal growth, with no significant differences in biomass, water content, or physiological stress indicators when compared to the control group. Nutrient uptake was found to be stable across treatments, although magnesium levels were below sufficiency thresholds without triggering visible deficiency symptoms. Overall, combining compost and biochar—particularly WB and GC—proved to be a viable strategy to reduce peat use while maintaining substrate quality and supporting robust plant growth. This approach proved effective across the different plant varieties tested, including Medicago polymorpha, Lolium perenne, and young olive plants, which together encompass a wide spectrum of agronomic and horticultural applications as well as contrasting growth and nutrient requirements. Adverse effects on early plant development can be avoided by carefully selecting and characterizing biochars, with specific attention to salinity and C/N ratio. This finding is crucial for the successful large-scale implementation of sustainable alternatives to peat. Full article

Olive pomace (OP) contains phytotoxic compounds that can impair plant growth and soil quality. Composting provides an effective method for detoxifying olive pomace (OP) and improving its suitability for agricultural use. Therefore, this study investigated the phytotoxic effects of raw olive pomace filtrate (OPF) on seed germination in radish (Raphanus sativus L.) and barley (Hordeum vulgare L.), as well as the impact of composted olive pomace (COP) on their growth. Seeds were exposed to OPF at concentrations of 0% (control), 1%, 3%, 5%, 10%, 20%, and 100%. Additionally, three composting treatments were evaluated: R1 (control: OP + barley straw), R2 (OP + barley straw + urea), and R3 (OP + barley straw + sheep litter). Results showed that OPF at concentrations of 10%, 20%, and 100% significantly reduced seed germination, with complete inhibition at concentrations > 10%. The COP treatments showed different physicochemical properties, such as R2 exhibiting better nutrient availability (C/N = 19, oil content = 0.04%). R3 had the highest concentrations of K (40,430.2 mg/kg) and P (6022.68 mg/kg). Results also indicated that R1 significantly reduced radish dry biomass production compared to barley, although R2 performed slightly better than R1 and R3. The findings highlight the need for proper compost stabilization to minimize the phytotoxicity and improve the agricultural potential of COP for improving soil health. Full article

Drought stress, a major abiotic factor, significantly threatens global agricultural productivity and food security. This study evaluated the potential of olive pomace compost to alleviate water stress in barley (Hordeum vulgare L.). A pot experiment compared well-watered (80% FC) and drought-stressed plants (40% FC), with compost applied at recommended (40 tons/ha) and double doses (80 tons/ha). Water stress reduced growth (fresh (−28.6%) and dry biomass, (−49.9%) shoot length (−20.45%)), photosynthetic pigments (chlorophyll a (−16.9%), chlorophyll b, (−52.16%) and carotenoids (−24.67%)), and water content, while impairing water relations, as shown by lower relative water content and higher water saturation deficit and consumption. Drought-stressed plants also exhibited elevated oxidative stress, indicated by increased malondialdehyde levels (+68.42%), and a modulated antioxidant defense system, with higher DPPH inhibition (+12.30%), with total phenolic content increasing by 220.70% and FRAP and ORAC values increasing by 55.18% and 37.44%, respectively. The application of olive pomace compost effectively mitigated these adverse effects, resulting in improved growth (ranging from 30% to 66%), pigment content (especially with double dose), and water relations; a lowering of oxidative stress (−37.5%); and moderation of the antioxidant response, indicating a reduced overall stress burden. The study findings show that olive pomace compost provides a sustainable and cost-effective strategy for improving crop resilience in water-scarce regions. By using this abundant agricultural waste, farmers can enhance soil health and maintain food security in the face of climate change. Full article

This study aimed to evaluate the environmental benefits of utilizing by-products from olive farms and olive oil mills within the framework of sustainable resource management and the reduction in agricultural waste, through an integrated circular approach that involves composting and bioenergy recovery. A total of 10.7–11.2 t/ha of biomass, including pruning residues and olive pomace, was generated, with a utilization efficiency of 63.5–67.5%. The energy potential of olive biomass was highlighted through assessments that revealed a theoretical generation potential of approximately 96 GJ/ha (25–28 MW·h/ha), primarily from repurposed woody biomass and pomace. The environmental analysis showed a 50–60% reduction in greenhouse gas emissions compared to conventional disposal, due to avoided open burning, carbon stabilization via compost, and the displacement of fossil fuels. Economically, the circular strategy yielded a net benefit of ~70 $/ha, with revenues from bioenergy and compost exceeding processing costs. Soil organic matter increased from 1.3% to 1.5% after compost application, improving fertility and water retention. The waste reduction percentage reached ~65%, significantly decreasing the volume of unutilized biomass. These outcomes, confirmed through statistical and correlation analyses, demonstrate a robust model for circular agriculture that enhances energy self-sufficiency, mitigates the environmental impact, and supports economic and agronomic sustainability. The findings offer a replicable framework for transforming olive farming waste into valuable bioresources. Full article

Fungi and soil bacteria are vital for organic matter decomposition and biogeochemical cycles, but excessive synthetic fertilizer use contributes to soil degradation and loss of biodiversity. Despite this, about 97% of soil microorganisms are unculturable, making them difficult to study. Metagenomics offers a solution, enabling the direct extraction of DNA from soil to uncover microbial diversity and functions. This study utilized metagenomics to analyze the rhizosphere of two-year-old Tonda di Giffoni hazelnut saplings treated with synthetic NPK, composted olive pomace, and an innovative fertilizer derived from sulfur-based agro-industrial waste stabilized with bentonite clay. Using 16S rDNA for bacteria and ITS2 for fungi, Illumina sequencing provided insights into microbial responses to different fertilizer treatments. The results highlighted a significant increase in the abundance of beneficial microorganisms such as Thiobacillus, Pseudoxanthomonas, and Thermomyces, especially when organic materials were included. Additionally, microbial biodiversity improved with organic inputs, as shown by increased species richness (Chao1) and diversity (Bray-Curtis) greater than 20% compared with NPK and unfertilized soils (CTR). These findings emphasize the importance of organic fertilization in enhancing soil microbial health, offering a sustainable approach to improving soil quality and hazelnut productivity. Full article

Olive cultivation is a key agricultural activity in Spain, primarily for producing oil. The extraction process of olive oil from the drupe yields a by-product known as ‘alperujo’, which can be composted and utilized as fertilizer. This research examines the impact of composted ‘alperujo’ on arthropod assemblages in the tree canopy, comparing it to mineral fertilization over the years 2021 and 2022. The study was conducted in two olive groves with different management systems (superintensive and traditional). Two types of sampling methods were used for the canopy: visual survey and sweep net. Under superintensive management, the presence and damage of Eriophyidae (Acari; Trombidiformes) in the shoots was significantly lower in the compost treatment in 2022 (20% of the shoots were occupied/damaged) compared to the mineral treatment (60% of the shoots were occupied/damaged). Araneae abundance was significantly higher (p = 0.033) in the compost treatment compared to the mineral treatment. However, under traditional management, no clear effect on arthropod assemblage was observed. In conclusion, the addition of compost to the superintensive grove helped to limit the presence of some arthropod pests compared to mineral treatment, contributing to a more sustainable crop. Grove type management appeared to play a significant role in the arthropod assemblages and effect of compost addition, but future research utilizing a greater number of groves (replicates) and an extended observation period should be performed to confirm these results. Full article

Olive oil extraction by two-phase systems generates a by-product called “alperujo” which presents several difficulties for its valorization. The present work evaluated an industrial approach, based on the application of thermal treatments to alperujo followed by solid/liquid separation using standard two-phase olive oil mill equipment. Treatments consisted of the thermo-malaxation of alperujo at 70 °C for 45 or 90 min, with or without acid addition, followed by solid/liquid separation in an industrial decanter. The solid was characterized concerning subsequent use for composting, while total and hydrophilic phenolics were analyzed in liquid for their recovery. Additionally, a laboratory-scale trial to compare phenolic purification by ethylic acetate extraction with chromatographic procedures was also included. The static respiration index showed that solid fractions presented higher susceptibility to biodegradation processes than raw alperujo. The phenolic content of treated liquid fractions was higher than in raw alperujo. Total phenolics were maximum at the longest exposure time without acid addition, while hydrophilic phenolics were highest at the shortest exposure time in acidified samples. The use of non-ionic resins seemed attractive for obtaining highly concentrated phenolic fractions. The proposed thermal treatments can be applied in olive oil industries, allowing in situ pomace valorization and the recovery of phenolic-enriched liquid fractions. Full article

Conducted in Southern Italy’s Calabria region, this study aimed to repurpose olive wastes, which are still a source of valuable biomolecules including plant nutrients, flavonoids, polysaccharides, and phenolic compounds, into compost to be used in sustainable agriculture as fertilizers, in alternative to synthetic substances. The compost underwent chemical analysis and soil fertility testing to support eco-friendly agricultural practices. Factors like extraction process, waste composition, and percentage of waste in composting were studied for their impact. The research evaluated compost fertilizing effectiveness by analyzing soil chemical and biological properties 180 days after the application. The results demonstrated that the proportion of olive oil waste and the olive oil extraction method significantly impacted compost quality and its environmental footprint. All composts improved soil properties but to a different extent. Compost olive waste 3 (OWC3; 34% olive oil waste, 33% buffalo manure, and 33% straw) was the most effective in enhancing soil fertility. Compost olive waste 1 (OWC1), with the same olive waste percentage as compost olive waste 2 (OWC2) but from a different extraction process, outperformed OWC2 in enhancing soil fertility and microbial activity. The research highlighted the importance of organic matter addition to soil and the significant role of both raw material percentage and extraction process in compost quality. Life cycle assessment indicated that OWC3 had the lowest environmental impact and the highest fertilizing power. Composting represents a practical way to manage organic wastes and improve soil quality, providing essential nutrients for soil health and ecosystem functioning. Full article

Fresh-cut leafy vegetables are produced in Southern Italy in very intensive crop systems under tunnel greenhouses in which continuous cropping has triggered soil organic carbon (SOC) depletion and the risk of degradation of soil fertility. A two-year trial of soil organic amendment was carried out on a private farm producing baby-leaf crops on a very poor OC soil (<1%). Biowaste compost, two types of olive pomace composts and buffalo manure were compared to evaluate their ability to recover a positive SOC balance and sustain crop growth and yield. The effects on soil health and crop system were studied by measuring different aspects such as SOC stock change and SOC sequestration rate, soil microbial biomass and nine enzyme activities, yields of rocket and concentration of nitrates in leaves. Soil amendments were distributed once a year at doses of 15 and 30 Mg ha⁻¹ as fresh matter without integration of mineral fertilizers. In our study, the SOC stock improved in the amended soils in a range of 4–6 Mg ha⁻¹, except for dose 30 of buffalo manure, with the highest values where biowaste compost was applied. Our data showed an increase in biological parameters in all the amended soils with respect to Control. In soil amended with olive pomace, however, compost mineralization rates likely did not match crops’ nutrient needs so the yields of rocket were lower than with the biowaste compost and buffalo manure. Biowaste compost showed the best results as it balanced the best C conversion efficiency, the higher increment of SOC and yields of rocket. Full article

Mediterranean agriculture asks for sustainable strategies to prevent actual soil organic matter decline rates. Composting agri-food by-products for application in farmland, besides contributing to a circular economy at regional or local scales, may improve soil resistance to physical degradation. Aggregate stability (AS) is a crucial property for building up such resistance. Olive pomace is an abundant by-product of the olive oil industry that may be valorized through composting. This study aimed to assess the influence on AS of olive-pomace-based composts (OPC) applied to a sandy loam Leptosol and a clay loam Fluvisol. To assess the effects of compost characteristics on AS, three OPCs resulting from different olive pomace proportions in the composting raw material (44, 31, and 25% by volume) were applied to aggregate samples in three doses (10, 20, and 40 t.ha⁻¹, plus control) with fine and coarse grain sizes. Controlled laboratory conditions subjected samples to daily wetting-drying cycles during a 30-day experiment. AS was measured by wet sieving. OPC application significantly increased AS in the Leptosol amended with fine (+15% vs. control) and coarse (+19%) grain-size compost. In well-aggregated Fluvisol, amendment induced a significant increase in AS only in the compost coarse grain size (+12%). The application dose significantly affected AS, with 10 t.ha⁻¹ being the best-performing dose. OPC applications in weakly aggregated soils are seemingly an encouraging soil management practice for improving soil resistance to physical degradation and reducing soil organic matter decline rates in Mediterranean farmland. Full article

Industrial production of olive oil generates large amounts of solid waste called ‘alperujo’. Its compost can fertilize many crops, especially olives. Furthermore, superintensive orchards are increasing their surface globally due to higher production and savings in different costs. Ants are considered an important part of the arthropod community in olive orchards and could even play a significant role in pest control. The tree canopy and ground were sampled to compare the ant assemblage in plots fertilized with compost and mineral products in two groves with different types of crop management (superintensive and traditional) over two years. The numbers of ants in both types of fertilization in each grove were not statistically different (p > 0.05), indicating that the type of fertilization did not have a significant impact on its populations in the ground or in the canopy, but the number of individuals was significantly higher in the superintensive grove than in the traditional grove (both in the ground and in the canopy, p < 0.01). The most frequent species in the ground were Pheidole pallidula, Plagiolepis smitzii and Aphaenogaster senilis (superintensive grove) and Pheidole pallidula, Tetramorium gr semilaeve, Plagiolepis pygmaea, and Tapinoma nigerrimum (traditional grove). In the canopy, the most frequent species were Plagiolepis spp. in both groves. Differences in ant densities and species between the groves could be due to the different management, especially of the soil, but it must be confirmed using more replicas and longer periods of study. Full article

Maintaining adequate levels of soil organic matter in Mediterranean agro-ecosystems is a pressing need due to the increasing evidence of climate change. The use of by-products of the olive oil industry as organic amendments could contribute to this goal. We report the results of a 2-year research carried out in southern Italy on a clay loam soil for evaluating the effects of different olive oil industry by-products on soil organic carbon and other related soil characteristics. The treatments were: (i) Olive mill wastewater (OMW), (ii) compost from olive pomace (CP1), (iii) compost from olive pomace in double quantity (CP2), and (iv) organo-mineral fertilizer (OMF). Soil samples, collected at a depth of 0–20 cm, were analyzed for total organic carbon (TOC), its extractable (TEC) and humic fractions (HC), and aggregate stability (Ist). In addition, soil macroporosity, water retention, and penetration resistance (PR) were evaluated. CP1 induced the largest increase in soil TOC, TEC, and HC content, and a significant improvement in Ist; the addition of a large quantity of organic carbon (CP2) did not determine a proportional increase in soil organic matter content. The aggregate stability of the CP2 was the lowest; nevertheless, the characterization of macroporosity indicated an improvement of soil structure functionality. With respect to control (OMF), OMW had a significant decrease in Ist and an increase in PR of the uppermost soil layer. Full article