The development of biofertilization strategies based on arbuscular mycorrhizal fungi (AMF) represents a promising approach to enhance crop productivity and soil health while reducing the environmental footprint of conventional fertilization. This study evaluated the effects of Glomus iranicum var. tenuihypharum inoculation on soil physicochemical properties, abundance and diversity of soil microbial communities, and physiological performance of nectarine (Prunus persica var. nucipersica) under Mediterranean field conditions. Soil inoculation with G. iranicum var. tenuihypharum significantly increased soil organic carbon, microbial biomass, and basal respiration, together with enhanced plant photosynthetic rate and stomatal conductance. These improvements were accompanied by early, but transient shifts in soil microbial community composition. The structure of the fungal community exhibited a marked alteration at the initial sampling point (30 days after application). Nevertheless, the differences in fungal community composition between inoculated and control soils diminished by the second sampling (90 days after application). This trend suggests a transient shift in plant-soil communication dynamics. Bacterial assemblages also responded, showing a reduction in Actinobacteria (e.g., Rubrobacter, Solirubrobacter) and an increase in Acidobacteria and Gammaproteobacteria. Additionally, the abundance of the ammonia-oxidizing archaeon Nitrososphaera increased following inoculation, suggesting potential effects on nitrification processes. Overall, Glomus iranicum var. tenuihypharum enhanced soil carbon storage and microbial activity, while stimulating plant physiological performance, without causing long-lasting alterations to the native microbiome. These results highlight the potential of products containing Glomus iranicum var. tenuihypharum as biofertilizers as part of a sustainable strategy to improve soil functionality, nutrient cycling, and crop productivity in Mediterranean fruit agroecosystems.

Aridity alters soil carbon (C), nitrogen (N) and phosphorus (P) stoichiometry, yet the implications of these processes for soil microbial functional traits and potentials at the genomic level remain poorly synthesized. Here we combine measurements of soil C, N and P pools and ratios with shotgun metagenomes from 200 natural ecosystems spanning major biomes worldwide. Across sites, increased aridity is associated with lower soil C:N and N:P (and C:P) ratios and with a coordinated shift in microbial functional potential. Genes linked to catabolic resource acquisition-including carbohydrate-active enzymes and pathways for degradation of plant litter and organophosphorus compounds-are declined as C becomes relatively scarce. In contrast, genes supporting anabolic investment in growth and drought resistance, such as RNA transcription, protein synthesis and intracellular transport, are increased. These patterns indicate that aridity-related change in soil elemental ratios is coupled to a broad shift from catabolic to anabolic strategies in soil microbiomes. By linking soil elemental ratios to microbial functional traits across biomes, our study provides a framework for anticipating how climate-driven drying may reorganize microbial metabolism with consequences for carbon and nutrient cycling.

Urban greenspaces have the potential to mitigate urban carbon footprints by storing soil organic carbon (SOC). Different management and plant communities associated with different types of urban greenspaces may hold contrasting SOC, as well as different proportions of particulate (POC) and mineral-associated organic carbon (MAOC). In addition, management could outweigh the effects of climate or soil properties as drivers of urban SOC storage, in contrast with natural environments. We analyzed SOC, POC and MAOC densities (kg m−2) in topsoil (0-10 cm) across 27 cities in the Iberian Peninsula with contrasting climatic and edaphic conditions. At each city, we compared four types of urban greenspaces (golf courses, roundabouts, urban farms, and parks) with a nearby natural ecosystem. Results revealed that, despite large differences in their typology, contrasting urban greenspaces stored comparable topsoil SOC and MAOC densities to natural ecosystems. Golf courses and urban farms also showed similar POC density to natural ecosystems, whereas parks and roundabouts had lower amounts of this carbon fraction. Consistent with global natural patterns, MAOC dominated over POC in the topsoil, and both carbon fractions showed an inverse correlation with mean annual temperature. While MAOC exhibited saturation at higher SOC levels, POC steadily increased. Although urban greenspaces are usually neglected in global soil carbon assessments, our study shows that, compared to natural ecosystems (median: 2.42 kg m−2; interquartile range: 1.77), these areas store an equally important density of carbon in the topsoil (median: 2.26 kg m−2; interquartile range: 1.30), and this carbon exhibits similar fraction dominance, temperature influence, and saturation across large spatial gradients.

Reforestation is widely promoted to mitigate soil degradation and desertification in semi-arid Mediterranean regions under future climate-change scenarios. The argan tree (Argania spinosa), a drought-resistant species, has been proposed as a potential alternative to pine (Pinus halepensis). We assessed soil physicochemical properties, organic matter (SOM) characteristics (content, molecular composition and thermogravimetric fractions), priming effects, microbial activity, and metagenomics-based characterization of microbial communities under argan and pine stands, compared to adjacent bare soil. Both argan- and pine-influenced soils showed significantly higher SOM content (12.13

ABSTRACT Soil nutrients are a major limiting factor for plant biomass, yet paradoxically, some of the most productive ecosystems thrive in nutrient‐poor soils. Here, we conducted a global field survey in 421 sites across all major biomes to investigate the environmental factors controlling the ratio between plant biovolume (a proxy for aboveground plant biomass) and topsoil macronutrient content (N, P, Ca, K, Mg and S) worldwide. We found that temperature and precipitation were the most important factors associated with this ratio. Warm and wet regions exhibited higher plant biovolume to soil nutrient content ratios than cold high‐latitude regions. We also identified an intriguing trade‐off: a negative correlation between soil microbial biomass and the plant‐nutrient ratio, suggesting that higher microbial biomass might be associated with lower plant biomass relative to soil nutrient content. These findings are instrumental for a better understanding of terrestrial carbon storage and anticipating ecosystem services under climate change.

Agricultural management is critical in shaping soil carbon (C) stocks, pools and fluxes. The soil priming effect (PE) is known as a key component of the global C cycle that reflects alterations in soil organic carbon (SOC) mineralization induced by fresh C inputs. Here, we show that priming can help to predict soil C content across European Long-Term Experiments (LTEs), a result which was maintained at continental and global scales. Results reveal that lower-intensity management significantly enhances PE in soils from European croplands. Conversely, high-intensity management led to lower or even negative PE. Management intensity influences PE directly through alterations in SOC and indirectly by modifying aggregates stability and microbial biomass. Both fertilization and tillage affect PE, with soils under organic fertilization and no-tillage showing higher values of PE. These findings advance our understanding of the long-term impacts of agricultural management on the C cycle at the continental scale.

The conversion of forests to cropland, driven primarily by agricultural expansion, can significantly alter ecosystem services and soil multifunctionality. In this study, we examined the effects of forest-to-cropland conversion in two semi-arid areas of Spain on soil chemical properties, microbial activity, and community structure. Sampling sites included perennial crops in soil A and annual crops in soil B, compared to Aleppo pine (Pinus halepensis) forests in both locations (PS and PC). Forest-to-cropland conversion and land use type influenced soil properties, microbial activity, and carbon and nitrogen cycles. We also observed significant differences (P < 0.05) in nutrient content for the two agricultural systems compared to the PS and PC forest soils. The annual crop showed a 61% decrease in total organic carbon, which reduced enzymatic activity compared to the forest soil (PS), where the implementation of perennial crops resulted in up to four times higher levels of nutrients such as phosphorus (P). The multifunctionality of the forest (PS) in soil B showed higher values than those of the cultivated lands, while in soil A, the forest (PS) only showed greater microbial activity. According to our study, the conversion of forests to perennial crops can promote soil management in semi-arid regions. These findings highlight the importance of implementing appropriate soil management strategies after the conversion of forest lands to agricultural use, prioritizing systems that maximize overall ecosystem functioning.

The overuse of mineral fertilization threatens long-term sustainability of through soil degradation, nutrient imbalances, and rising production costs. Sustainable fertilization strategies based on recycled organic materials offer a potential solution to improve soil functioning while maintaining yield and economic viability. In this three-year field study in a Mediterranean maize agroecosystem, we evaluated the effects of organic, organo-mineral, and mineral fertilization on soil chemical al biological properties, maize productivity, and fertilization efficiency. Treatments included mineral NPK, compost, sewage sludge, struvite, and the combinations of organic materials with struvite, at equivalent total nutrient inputs across treatments. To assess soil health, we measured key chemical and biological parameters, including soil organic carbon (SOC), nutrient availability, microbial biomass, and enzyme activity, which were integrated into a unified Soil Health Index (SHI). Organic and organo-mineral treatments progressively enhanced nutrient availability, microbial biomass, and enzyme activities compared with NPK fertilization, leading to higher soil health values over time, particularly under sludge and compost-based treatments. Maize yield did not differ among fertilization strategies, indicating that soil health gains were achieved without productivity tradeoffs. Further, integrating SHI with agronomic and economic metrics revealed that sludge-based fertilization maximized soil health maintained per unit of yield produced and substantially improved fertilizer cost efficiency relative to NPK. These results demonstrate that circular fertilization strategies can improve soil functioning and resource-use efficiency while sustaining maize production, supporting their adoption as a viable pathway toward more resilient and cost-effective agroecosystems.

Several biosolarization approaches have been investigated to reduce pesticide residues in agricultural soils, which can potentially affect soil health and microbial communities. This study explored biosolarization with green manures from fresh plant material (oats/vetch, mustard, radish, and red clover), previously used as cover crops, to degrade nine pesticide residues in soil. It also examined the effects on soil health indicators, such as basal respiration and microbial biomass. A pot experiment was conducted with pesticide-contaminated soil from SE Spain, amended to 10 % with green manure, during the summer in a greenhouse. Two control treatments without green manure were performed: untreated and solarized. Biosolarized soils exhibited significantly higher pesticide degradation (e.g., from 31 % for myclobutanil with radish) than controls (e.g., from 1 % for pendimethalin in untreated soil and from 7 % for myclobutanil in solarized soil). Basal respiration in biosolarized soils peaked at 15 days after amendment (5.5-11.2 mg CO2-C kg-1 soil day-1) compared to controls (1.7-1.8 mg CO2-C kg-1 soil day-1). Microbial biomass was four times higher in biosolarized soils than in the controls 15 days after amendment. The results demonstrate that biosolarization with green manure is a feasible tool for recovering pesticide-polluted soils while enhancing soil biological health.

Use of synthetic microbial communities (SynComs) is a promising approach that harnesses nature-based solutions to support soil fertility and food security, mitigate climate change impacts, and restore terrestrial ecosystems. Several microbial products are in the market, and many others are at different stages of development and commercialization. Yet, we are still far from being able to fully harness the potential and successful applications of such biotechnological tools. The limited field efficiency and efficacy of SynComs have significantly constrained commercial opportunities, resulting in market growth falling below expectations. To overcome these challenges and manage expectations, it is critical to address current limitations, failures, and potential environmental consequences of SynComs. In this Viewpoint, we explore how using multiple eco-evolutionary theories can inform SynCom design and success. We further discuss the current status of SynComs and identify the next steps needed to develop and deploy the next generation of tools to boost their ability to support multiple ecosystem services, including food security and environmental sustainability.

Ecosystem functioning is potentially dependent on the relationships between soil microbial diversity and biomass. Yet, it remains unclear how land use and climate influence these relationships. Here, we (i) analysed relationships and ratios between richness and biomass of bacteria and fungi in ~500 soils across Europe, including three land-use types (woodlands, grasslands and croplands) and climates (cold, temperate and arid) and (ii) identified the driving factors of changes in richness:biomass (R:B) ratios. Richness and biomass of soil bacteria and fungi followed a unimodal pattern, with a peak in mid-levels of biomass. This pattern was more evident in bacteria and more clearly exerted by land use than by climate. Bacterial R:B ratios decreased with land use in the following order: croplands > woodlands > grasslands. Fungal R:B ratios decreased as follows: grasslands > croplands > woodlands. Climate was found to interact with land use. In this way, arid climate tended to increase bacterial R:B ratios in the different land uses; however, the agricultural practices associated with croplands seem to buffer this effect. In fungi, the interactive effect of land use and climate was less straightforward than for bacteria. According to our models, soil organic carbon (SOC) and total nitrogen (N) in bacteria and SOC in fungi were identified as the primary predictors of R:B ratios. Therefore, factors related to climate and land-use change with impact on SOC and N contents are potential disruptors of soil microbial R:B ratios. This study clarifies the diversity:biomass relationships across different land uses and climates.

Fecal samples are widely used as a proxy for studying gut microbiome composition in both human and animal research. Fecal metaproteomics provides valuable insights by tracking changes in the relative abundance of microbial taxa and their protein functions. To ensure reliable results, it is crucial to minimize alterations in the metaproteome occurring from sample collection to protein extraction. Therefore, employing effective stabilization methods is essential to preserve the integrity of the fecal metaproteome from sample collection to laboratory analysis, particularly over long distances or when rapid freezing options are not readily available. In line with these needs, the second edition of the Critical Assessment of MetaProteome Investigation (CAMPI-2) was specifically focused on testing sample stabilization protocols to be applied before metaproteomic analysis. This collaborative multicenter study assessed the ability of five different stabilization methods, based on two commercial devices and three specific reagents (acetone, lithium dodecyl sulfate, and an RNAlater-like buffer), respectively, to stabilize the fecal metaproteome during room-temperature storage (14 days) and shipment to mass spectrometry facilities. The five methods were tested simultaneously by eight different laboratories across Europe, using aliquots from the same fecal sample. After protein extraction and digestion, duplicate aliquots of the resulting peptides were analyzed independently by two mass spectrometry facilities at distinct international locations. Analysis of the mass spectrometric data using two different search engines revealed that the fecal metaproteome profile differed considerably depending on the stabilization method used in terms of richness, alpha and beta diversity, reproducibility, and quantitative distribution of main taxa and functions. Although each method showed unique strengths and weaknesses, a commercial swab-based device stood out for its remarkable reproducibility and ranked highest for most of the metrics measured. CAMPI-2 allowed a robust evaluation of five different methods for preserving fecal metaproteome samples. The present investigation provides useful data for the design of metaproteomics and multi-omics studies where fecal sampling cannot be immediately followed by long-term storage at − 80 °C. Further optimization of the tested protocols is necessary to improve stabilization efficiency and control bias in the taxonomic and functional profile of the gut microbiome.

Urban greenspaces play a critical role in conserving biodiversity and provide multiple ecosystem services from carbon sequestration to pathogen regulation. Yet, little is known about how contrasting urban greenspaces, varying in land-use intensification levels, influence the biodiversity and ecosystem functions across large environmental gradients. Here, conducted a standardized field survey in 51 cities from the Iberian Peninsula to evaluate the impacts of land-use intensification on 36 ecosystem indicators and 11 above- and belowground biodiversity and ecosystem services. At each city, we sampled five plots along a land-use intensification gradient, from less managed natural or semi-natural ecosystems, city parks and roundabouts to more heavily managed golf courses and urban farms. We showed that land-use intensification decouples biodiversity and ecosystem functions across urban greenspaces. Natural or semi-natural ecosystems and city parks supported the highest levels of multiple ecosystem services, particularly carbon sequestration, but exhibited relatively low soil and plant species richness. In contrast, the opposite pattern was found in urban farms, at the highest end of our land intensification gradient. These findings reveal that the management of urban greenspaces is heavily influenced by important trade-offs between biodiversity and ecosystem services, highlighting that the one-size-fits-all solution is not adequate when pursuing multiple management goals.

Halotolerant plant growth-promoting bacteria (PGPB) have great potential for alleviating salinity stress in crops. However, the current methods used with these bacteria are typically based on one-time inoculations, including soil basal application, seed dressing and plant infestation, all of which make it difficult to guarantee the desired plant effects. Here, we investigated the effects of seven halotolerant PGPB individually applied through a drip irrigation system in small quantities and at high frequency during the plant’s growth period on the soil physicochemical properties, plant agronomic performance and bacterial community in saline soil. Our findings revealed that drip irrigation with halotolerant PGPB notably decreased the soil pH and electrical conductivity while increasing the yield and fruit quality of jujube plants. Specifically, the Bacillus licheniformis (BL) and Bacillus mucilaginous (BM) treatments outperformed the control (no PGPB irrigation) by increasing the yield and vitamin C (VC) content by 23 % and 22 %, respectively. Additionally, the presence of halotolerant PGPB enriched the diversity of the bacterial community in the jujube rhizosphere and increased the relative abundance of beneficial bacterial groups at both the phylum (e.g., Cyanobacteria and Nitrospirota) and genus (e.g., Psychrobacter, Flavobacterium, and Steroidobacter) levels. Bacterial interactions, represented by co-occurrence networks, were more complex in the treatments involving PGPB irrigation, contributing to the transformation of the network keystones involved in soil nutrient cycling. Applications of BL, Bacillus cereus (BC), and BM reduced the soil salinity and increased the soil available nutrient contents and plant antioxidant enzyme activities, alleviating salinity stress and resulting in increases in crop yield and quality. This study highlights the feasibility and efficiency of applying halotolerant PGPB via drip irrigation in saline soil environments, thereby enhancing crop performance under salt stress.

With global phosphate rock resources declining for conventional fertilizers, there is growing interest in exploring alternative, more sustainable materials to enhance soil fertility and crop yield production. Additionally, leveraging microorganisms to improve phosphorus (P) availability in soils is an appealing approach for sustainable agriculture. This study evaluates the effects of different P-rich materials, including struvite (STRU), meat and bone meal (MBM), and phosphate rock (PR), combined with a microbial consortium with P-solubilizing and plant growth-promoting capabilities, on P availability and plant growth in two soils with contrasting physicochemical properties. To achieve these goals, a pot experiment was conducted to assess P content in soil, ryegrass, and microbial biomass, along with microbial enzyme activity and community composition using microbial fatty acid analysis. The experiment involved two soils with contrasting characteristics, amended with conventional monoammonium phosphate (CHEM), STRU, MBM, and PR, with or without microbial inoculation. Soil characteristics and the type of P fertilizer significantly influenced P availability, ryegrass uptake, and plant yield. Microbial inoculation did not increase soil P or ryegrass yield. Fatty acid analysis showed microbial community changes with soil characteristics and fertilizer. Struvite performed similarly to CHEM, while MBM was less effective than struvite but better than PR as a P fertilizer. Our study found that soil characteristics and the type of phosphate fertilizer affected soil P dynamics in the soil–plant system. Recycled P-based fertilizers offer sustainable alternatives to synthetic ones, potentially alleviating agricultural challenges.

This study assesses the effects of various organic amendments, included vegetable compost from garden waste, compost from vegetable and fruit residues, and sewage sludge stabilized, applied individually and in mixtures, on restoring degraded quarry soils in arid Southeast Spain. Changes in soil physical and chemical properties, enzyme activities, fatty acid methyl-esters and organic matter were monitored to assess restoration relative to unamended and natural soils. Amendments led to significant organic matter improvements, microbial community structure and activity compared to unamended ones. However, results varied depending on amendment type and weather conditions, which influenced soil moisture and temperature. Organic matter increased by up to 2.4 % above control (0.53 %), approaching natural soil levels. Pyrolysis-GC/MS revealed molecular changes, emphasizing persistence and transformation of specific compounds over time. Soils with vegetable compost had 15-20 % higher lignin derivatives, aromatic compounds, and polysaccharides than control, while sewage sludge increased nitrogenous compounds. Amended soils showed significantly higher enzyme activity than controls, indicating enhanced microbial function. Sewage sludge and mixed treatments showed microbial lipid levels 20-30 times higher than controls, while vegetable compost treatments led to 8-10 times higher values, suggesting enhanced microbial biomass and diversity. These findings support the use of organic amendments to accelerate soil recovery, particularly through enhanced biological activity and improved organic matter quality. Amendment type shapes soil recovery, offering guidance for optimizing restoration strategies. Vegetable compost and sewage sludge improve soil quality and support waste valorization in a circular economy, but their use requires careful management and longterm sustainability evaluation.

Soil microbes drive ecosystem function and play a critical role in how ecosystems respond to global change. Research surrounding soil microbial communities has rapidly increased in recent decades, and substantial data relating to phospholipid fatty acids (PLFAs) and potential enzyme activity have been collected and analysed. However, studies have mostly been restricted to local and regional scales, and their accuracy and usefulness are limited by the extent of accessible data. Here we aim to improve data availability by collating a global database of soil PLFA and potential enzyme activity measurements from 12,258 georeferenced samples located across all continents, 5.1% of which have not previously been published. The database contains data relating to 113 PLFAs and 26 enzyme activities, and includes metadata such as sampling date, sample depth, and soil pH, total carbon, and total nitrogen. This database will help researchers in conducting both global- and local-scale studies to better understand soil microbial biomass and function.

Future phosphorus (P) fertilizer availability faces challenges due to limited phosphate rock mines and strict quality regulations regarding Cd contents in phosphate rock. In this study, conventional fertilization was partially substituted with meat bone meal (MBM), sludge (S), and the organo-mineral combination of S plus MBM (SMBM), in a wheat agroecosystem. We investigated the impact of fertilization treatments and crop phenological stages on P availability, crop yield, and soil microbial responses. Analysis included enzyme activities, microbial biomass, and the composition of bacterial and fungal communities using metabarcoding. Additionally, we estimated functional genes related to the P cycle through qPCR. Crop yield and nutrient content in plants and soil were also determined. Replacing traditional fertilization with MBM and SMBM maintained crop yield at levels equivalent to conventional fertilization. S and SMBM produced 70

Soil organic carbon (SOC) is essential in semi-arid agricultural land for enhancing soil health, particularly through the promotion of microbial activities. This study assessed the impact of different agronomic practices on soil properties, microbial communities, and SOC levels in semi-arid Moroccan wheat fields. Three treatments were investigated: eucalyptus (Eucalyptus spp.) companion planting (EU), and fallowing with harvest residue mulching (FA), with the latter involving both short (3 months; FAS) and long (15 months; FAL) fallow periods. The study revealed significant variation in soil characteristics and microbial communities between these agronomic management regimes. Notably, soils managed with FAL contained elevated SOC levels (1.2%) compared to other treatments (FAS and EU) which show lower SOC range (0.62–0.86%). Both labile C (water-soluble carbon) and recalcitrant C (humic substances) were increased by FAL. Additionally, soil microbial biomass and dehydrogenase activity were observed to be high in FAL-managed soils, along with increased levels of extracellular enzymes related to nutrient cycling (β-glucosidase, alkaline phosphatase, and urease). Phospholipid fatty acid (PLFA) analysis indicated positive correlation between carbon content in soils and microbial populations. In contrast, soils managed with EU had significantly lower SOC levels, possibly due to differences in carbon fractionation. FAL increased soil enzymatic activities and enriched the microbial community when compared to EU management. In conclusion, this study indicated the importance of fallowing and fallowing period for conservation of SOC, and potential to mitigate negative effects of biophysical constraints on agricultural productivity in semi-arid soils of Northwest Africa.