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Excessive use of nitrogen fertilizer and inappropriate fertilization designs have negative results in agricultural ecosystems, such as considerable nitrogen losses through nitrogen dioxide (NO2) soil leaching and ammonia NH3 volatilization. In addition, climate change, with rising summer temperatures and reduced precipitation, leads to production declines and water shortages in the soil. This review aims to highlight the characteristics of natural zeolite and focus on their multiple uses in agriculture. These minerals are tectosilicates showing an open three-dimensional structure involving the cations required to balance the framework electrostatic charge of aluminum and silicon tetrahedral units. Different research groups reported more than fifty natural zeolites; chabazite, clinoptilolite, phillipsite, erionite, stilbite, heulandite, and mordenite are the most well-known. Zeolites are great tools to help the farmer and agronomist cope with several issues, such as soil or water pollution, contamination by heavy metals, loss of nutrients, and loss of water-use efficiency (WUE) of drylands. These natural crystalline aluminosilicates are considered soil conditioners to improve soil chemical and physical properties, such as saturated hydraulic conductivity (Ks), infiltration rate, cation exchange capacity (CEC), and water-holding capacity (WHC). Owing to their properties, these materials are able to reduce nitrate leaching and ammonia volatilization. Zeolites are also known for their carrying capacity of slow-release macronutrients, micronutrients, and fertilizers. However, the potential of these materials in agricultural areas is apparent, and zeolites show the promise of contributing directly to improve agricultural ecosystems as a sustainable product.

The aim of this study was to evaluate the effectiveness of a landfarming process (LP) in recovering sediments at different biodegradation phases: phytoremediated dredged sediments (PDS) and fresh dredged sediments (FDS). The PDS landfarming was applied to (1) reduce residual contamination and (2) improve the biological activities in order to obtain a decontaminated matrix rich in organic matter and enzymatic activity to be reused as agronomic substrate. In 3 months of LP, a microbial activity stimulation (from 7 to 48%) and a decrease in organic contamination (about 15%) were recorded. In addition, no phytotoxicity and the content in total organic carbon and nitrogen make the sediments suitable to be reused in agriculture. The FDS landfarming was carried out to (1) reduce water content, (2) transform the organic matter into a more stable form, and (3) decrease organic contaminant level. Five months of LP led to a considerable reduction in water content (40%) and to the activation of microbial biomass metabolism (from 4 to 50 times higher), which achieved proper mineralization of organic matter and contaminants (polycyclic aromatic hydrocarbons near to zero and a total petroleum hydrocarbon reduction of about 60%). The LP also enhanced the stoichiometric ratios of nutrients and enzymes. In conclusion, the LP was a promising and economical methodology to improve the physical, chemical, and biological properties of polluted sediments at different biodegradation phases, creating a substrate ready for several environmental applications. Notably, the PDS resulted appropriate for agricultural use and FDS for civil applications.

The purpose of this study was to monitor and model indicators of soil contamination, organic matter evolution and biochemical processes involved in a long-term phytoremediation process. Populus nigra L. , Paulownia tomentosa Steud ., Cytisus scoparius L. and natural vegetation were used in differently contaminated areas (high, medium and low levels of contamination). Parameters indicating contamination (total petroleum hydrocarbons (TPH) and heavy metals) and agronomic (C, N and P) and functional (enzyme activities) soil recovery were monitored for 3.5 years. Three subareas with different levels of contamination (high, medium and low) were identified according to the Nemerow Index. A considerable decrease in TPH (52% on average) over time in the whole site was measured, while the metal reduction was only of about 22% at surface level. A stimulation in metabolic soil processes and improvement in the chemical quality of the soil was also observed throughout the experimental site. Statistical analysis modelling showed that the contaminant content decreased following a one-phase decay model, while the dramatic increase in enzyme activities could be represented by an exponential growth equation. On the basis of our data, it is possible to conclude that the initial contamination level affected neither the decontamination process nor the improvement in soil quality, which occurred similarly in the three different contaminated areas.

Monitoring the soil–plant system in forest ecosystems is crucial for preserving their ecological functions and services. This study assessed carbon and nitrogen stable isotopes and ecoenzymatic stoichiometry as suitable indicators for characterizing the soil–plant system as a functional unit of ecological processes. To this end, in June 2021 six plots (1 m2 each) were selected in two typical Mediterranean forest ecotypes: a coastal stone pine forest (Pinus pinea L., PF) and a meso-hygrophilous broadleaf forest (RV). Soil samples (0–15 and 15–30 cm depth) and litter samples (40 × 40 cm) were collected and characterized in terms of physical, chemical and biochemical properties. t-tests revealed significant differences between RV and PF, indicating distinct microbial nutrient acquisition strategies. The higher C:N ratio in PF suggested lower litter quality and greater recalcitrance to microbial decomposition. Consistently, RV showed a more pronounced 13C and 15N enrichment from litter to SOM down to a 30 cm depth, confirming faster organic matter decomposition and mineralization. Enzyme activity patterns supported these findings. The higher β-glucosidase and butyrate esterase activities in RV reflected its greater microbial potential to activate biogeochemical cycles. Both forests exhibited a higher microbial demand for C and P than for N to maintain ecological stoichiometric balance, with stronger C limitation at the surface and P limitation in the subsoil, particularly in RV soil. This integrated monitoring approach provides insights into nutrient cycling and ecosystem resilience and offers tools to evaluate ecosystem functionality under changing environmental conditions, supporting sustainable forest management.

Nature-based solutions (NbS) are multidimensional, resource-efficient, and sustainable growth approaches to cope with current challenges, including biodiversity and carbon loss, pollution, climate change and land degradation. Amongst NbS, urban forestry is an important tool to enhance environmental resilience and sustainability, providing useful ecosystem services for human well-being. In this context, using suitable soil and plant indicators allows us to evaluate the efficiency of urban forestry in sustaining ecosystem functionality. Effective indicators should be sensitive to environmental changes and representative of ecological processes. Many studies focus on the selection of soil or plant indicators. The prior investigations considered soil–plant interaction and the related complex heterarchical and bidirectional effects involving plant strategy and soil biota. The choice and the use of indicators related to the soil–plant system could be an innovative strategy to better assess the following: (1) the ability of soil to support healthy plants and their ability to improve air quality; (2) the effect of urban forestry on ecological processes, in particular carbon and nutrient cycles. This review investigates the suitability of soil–plant system indicators related to nutrient cycles, e.g., ecological stoichiometry, enzyme activity and stoichiometry, and carbon and nitrogen stable isotopes, as valuable tools for planning and evaluating the effectiveness of urban forestry interventions.

Heavy metal contamination in soil and the resulting groundwater pollution are common at many brownfield sites. Soil washing, which dissolves contaminants into a washing solution to separate them from the soil matrix, has emerged as a promising remediation strategy. This study assessed the feasibility of applying soil washing to Pb-contaminated soil collected from an industrial area within the Trieste Port Authority (Italy) through a series of leaching tests. Batch tests were conducted using ethylenediaminetetraacetic acid (EDTA)-based extractants combined with various reducing agents to identify the most effective and environmentally sustainable washing solution. The results show that coupling EDTA with hydroxylamine hydrochloride or sodium dithionite significantly enhanced Pb solubilisation compared with EDTA alone, with dithionite emerging as the most suitable reducing agent due to its lower toxicity and reduced environmental impact. Sequential extraction tests revealed that up to 50% of total Pb could be removed after repeated washing cycles. Column leaching tests further confirmed the high efficiency of the EDTA–sodium dithionite system, achieving Pb removal rates of approximately 70% under continuous flow conditions. Overall, the results demonstrate that EDTA combined with low-dose sodium dithionite provides an effective and practical remediation strategy for heavily polluted industrial soils.

Co-composting efficiently reclaims dredged sediments (S) and green waste (GW), creating stable products for agricultural applications. However, the use of S-GW co-composts can be limited by legislative thresholds, especially for co-composts with a high S percentage. The evaluation of S-GW co-compost stability by biological assessment can allow for a better understanding of S and GW recycling, as well as the S-GW co-compost application. For this purpose, the microbial biomass, composition, respiration, and eco-enzyme stoichiometry (EST) were assessed, coupled with chemical analysis, in the co-composting of S and GW in different ratios. The Photinia x fraseri and Viburnum tinus L. growth was monitored in a plant trial, comparing the studied co-composts with a control substrate. The EST approach was applied as an indicator of the co-composting stability during the process and after the plant cultivation. The chemical and biological parameters confirmed the suitability of co-composting in the GW and S recovery and the EST approach highlighted a better stability for the 3S:1GW co-compost at the end of the process and after plant cultivation. Viburnum tinus showed a similar growth to the control, while Photinia x fraseri resulted in being more sensitive to the co-compost. The biological assessments were good indicators of the S-GW compost stability for their application in crop cultivation.

The ornamental nursery industry is steadily growing in Europe, and a consequent increase in the demand for substrates related to container plant cultivations is expected in the coming years. Currently, substrates consist in part or entirely of peat, a non-renewable resource with concerns about its environmental impact due to extraction, transport, and use. Therefore, it is essential to focus on alternative materials, particularly waste by-products to be recycled as components of substrates to achieve more sustainable cultivations. In this study, substrates obtained by mixing co-composted dredged sediments (S) and green waste (GW) in different ratios (1:3; 1:1; 3:1) were tested for cultivation, and plant growth was compared with a control growing media (peat and pumice in a 1:1 ratio). The cultivation trial lasted for one year and was carried out on two potted ornamental evergreen shrubs (Photinia × fraseri and Viburnum tinus). The results showed that the plant growth parameters of both species, occurring in substrates with co-composted materials, were not significantly affected compared to the control, with the exception of below-ground biomass in V. tinus. Moreover, a Life Cycle Assessment (LCA) analysis was carried out to quantify the greenhouse gas emissions (GHG) deriving from the replacement of peat with the other proposed substrates. The functional unit was 10 L (Ø 24 cm) potted plants and the results were expressed in kg of CO2 equivalent (kg CO2eq). We demonstrated that the replacement of peat-based substrates with the alternative substrates was able to reduce the GHG emission by an average of 11.56 to 23.13%. Higher GHG emissions were related to the cultivation phase (0.9 kg CO2eq/plant), and while comparing substrates, we obtained an average percentage reduction of 28.1% to 59.6%. Thus, our results suggest that co-composted mixtures of dredged sediments with green waste could be used as sustainable techno-soils for pot nursery cultivation of ornamental species with reduced environmental impact.

In 2013, a pilot experimental field of about 15 ha was set up within the basin of Lake Massaciuccoli (Tuscany, Italy) in order to compare different management strategies—a paludicultural system (PCS), a constructed wetland system (CWS), a nearly-natural wetland system (NWS)—for peatland restoration after almost a century of drainage-based agricultural use (CS). After five years, changes in peat soil quality were investigated from a chemical, biochemical, and ecoenzymatic perspective. The soil in CS was mainly characterized by oxidant conditions, higher content of overall microbial activity, low levels of easily available phosphorus for vegetation, and medium total carbon content ranging from 25.0% to 30.7%. In PCS, the levels of total carbon and the content of bioavailable P were higher, while the oxidant conditions were lower compared to the other systems. As expected, the soils in CWS and NWS were characterized by the most reduced conditions and by the highest levels of arylsulphatase activity. It was noteworthy that soils in the NWS systems were characterized by the highest level of nonavailable P. Outputs from ecoenzymatic activity confirmed the physico-chemical and biochemical results.

A significant example of circular economy application concept is the recycling of wastes through co-composting to obtain techno-soils and composts. The objective of this paper was to demonstrate that the co-composting of Posidonia oceanica residues with decontaminated sediments is an effective method to manage two kinds of waste and transform them in a suitable material for the preparation of growth substrates. To demonstrate the effectiveness of the co-composting process, a protocol, involving physical–chemical, biochemical, and toxicological parameters, has been followed. Moreover, to evaluate the quality of the different Posidonia-based composts, the characteristics have been compared with threshold values proposed in the Italian regulation for plant growth substrates and to specific parameters from the scientific literature. All the obtained composts responded to the main characteristics for composting and growing media preparation provided in national and international regulations, in terms of pH (6.7–7.6), electrical conductivity (0.13–0.30 dS/m), and total organic carbon content (6.62–27.9 C%). Moreover, results about humic carbon (16.6–21.9 C%), germination index (139–158%), enzymatic activities (B-glucosidase: 3538–5367 mmol MUB/kg ds H), bulk density (0.30–0.83 g/cm 3 ), and cation exchange capacity (43.3–126 meq/100 g ds) proved the quality of the P. oceanica and sediment based composts. These results are an endorsement of Posidonia with sediment-based composts use as a constituent of techno-soils and, as a component for the preparation of nursery growth substrate. It is possible to claim that the co-composting process is an alternative management strategy for decontaminated sediments and P. oceanica residues to be recommended. Adequate policies are needed in order to recycle Posidonia oceanica residues and decontaminated sediments, namely two kinds of waste, into a secondary raw material, namely techno-soil, thus implementing the concept of the circular economy. Graphic Abstract