Explainer: Microbiomes & soil health in ecosystems

Why It Matters

A single gram of healthy soil contains up to 10 billion microorganisms representing thousands of species, making soil the most biodiverse habitat on the planet (Global Soil Biodiversity Initiative, 2025). These microbial communities drive approximately 90 percent of soil nutrient cycling, underpinning the productivity of ecosystems that supply 95 percent of global food (FAO, 2025). Yet an estimated 33 percent of the world's soils are degraded, costing the global economy US$10.6 trillion annually in lost ecosystem services (UNCCD, 2024). The carbon sequestration potential of improved soil management ranges from 1.5 to 3.5 Gt CO₂ per year, equivalent to roughly 5 to 10 percent of current global emissions (Minasny et al., 2024). For sustainability professionals, understanding soil microbiomes is no longer optional: the EU Soil Monitoring Law adopted in 2024, the Kunming-Montreal Global Biodiversity Framework's soil targets, and emerging nature-related financial disclosures all place soil health at the centre of compliance and reporting obligations.

Key Concepts

Soil microbiome composition. Soil microbial communities comprise bacteria, archaea, fungi, protists and viruses. Bacteria typically dominate by abundance, with Actinobacteria, Proteobacteria and Firmicutes among the most prevalent phyla. Fungi, though less numerous, contribute disproportionately to soil function through extensive hyphal networks. Mycorrhizal fungi alone form symbiotic associations with approximately 90 percent of terrestrial plant species, facilitating nutrient uptake and water absorption (Tedersoo et al., 2024).

Nutrient cycling. Microorganisms mediate the cycling of nitrogen, phosphorus, sulphur and carbon through mineralisation, nitrification, denitrification and decomposition processes. Nitrogen-fixing bacteria such as Rhizobium convert atmospheric nitrogen into plant-available forms, reducing the need for synthetic fertilisers. Phosphate-solubilising microbes unlock bound phosphorus from mineral surfaces, increasing its bioavailability.

Soil organic carbon. Soil stores approximately 2,500 gigatonnes of organic carbon in the top two metres, more than three times the amount held in the atmosphere (Lal, 2024). Microbial activity determines whether organic matter is mineralised and released as CO₂ or stabilised into persistent soil organic matter through mineral association and aggregate formation. The balance between these pathways is central to soil carbon sequestration potential.

Soil health indicators. Modern soil health assessment integrates biological, chemical and physical parameters. Biological indicators include microbial biomass carbon, enzyme activity (e.g., beta-glucosidase, phosphatase), respiration rates, and microbial diversity measured through DNA sequencing. The Haney Soil Health Test and Cornell's Comprehensive Assessment of Soil Health are widely adopted frameworks that score soils on multiple functional dimensions.

The rhizosphere. The narrow zone of soil surrounding plant roots, known as the rhizosphere, hosts microbial populations 10 to 100 times denser than bulk soil. Plants exude sugars, amino acids and organic acids through their roots, recruiting beneficial microbes that suppress pathogens, enhance nutrient uptake and improve drought tolerance. This plant-microbe dialogue is a primary lever for managing soil health through crop selection, cover cropping and reduced tillage.

How It Works

Soil microbiome management operates through a set of interconnected practices and assessment frameworks.

1. Baseline assessment. Effective management begins with characterising the existing soil microbiome. Next-generation sequencing technologies, particularly 16S rRNA gene amplicon sequencing for bacteria and ITS sequencing for fungi, enable rapid profiling of microbial community composition. Shotgun metagenomics provides deeper functional insights, revealing the metabolic potential of soil communities. Companies such as Biome Makers and Trace Genomics offer commercial soil microbiome testing that returns actionable reports within two to three weeks.

2. Management interventions. Practices that increase organic matter inputs, reduce disturbance and diversify plant communities reliably improve soil microbiome health. Cover cropping introduces living roots year-round, sustaining rhizosphere communities during fallow periods. Reduced or no-till farming preserves fungal hyphal networks and soil structure. Compost and manure applications provide substrates that feed decomposer communities. Crop rotation and intercropping diversify root exudate profiles, promoting microbial diversity. A 2025 meta-analysis across 148 field trials found that combining cover crops with reduced tillage increased microbial biomass carbon by 28 percent and soil organic carbon by 12 percent over five years (Kallenbach et al., 2025).

3. Microbial inoculants. Bio-inputs, including mycorrhizal inoculants, nitrogen-fixing bacteria and plant growth-promoting rhizobacteria (PGPR), can be applied directly to seeds or soils. The global biostimulant market reached US$4.2 billion in 2025 and is projected to grow at 11 percent CAGR through 2030 (MarketsandMarkets, 2025). However, inoculant efficacy depends heavily on compatibility with native soil communities, climate conditions and application method. Independent field trials show variable results, with inoculant-driven yield improvements ranging from 5 to 20 percent depending on context (Kaminsky et al., 2024).

4. Monitoring and feedback loops. Ongoing monitoring tracks whether interventions translate into measurable improvements. Enzyme assays, respiration tests and periodic DNA sequencing provide longitudinal data. Remote sensing proxies, including soil moisture, NDVI and thermal imaging, offer landscape-scale indicators of soil health trends. The integration of sensor networks with microbiome data is an emerging frontier, with platforms like ChrysalisIQ and Yard Stick PBC combining in-field sensors with machine learning to estimate soil carbon and biological activity in near-real time.

What's Working

Regenerative agriculture at scale. General Mills committed to advancing regenerative agriculture on 1 million acres of farmland by 2030 and reported in 2025 that enrolled farms show a 15 percent increase in soil organic matter and a 22 percent increase in water infiltration rates compared to conventionally managed neighbours (General Mills, 2025). Soil microbiome analyses across the programme reveal significantly higher fungal-to-bacterial ratios, an indicator of mature, carbon-stabilising communities.

The "4 per 1000" initiative. Launched at COP21, this initiative aims to increase global soil organic carbon stocks by 0.4 percent per year, which would offset a substantial fraction of anthropogenic CO₂ emissions. By 2025, 700 organisations across 80 countries had joined (4 per 1000, 2025). Participating farms in France demonstrated annual soil carbon accrual rates of 0.3 to 0.7 percent through combined cover cropping, compost application and agroforestry practices.

Brazil's degraded-pasture recovery. Brazil's ABC+ Plan (Low Carbon Agriculture) targets restoration of 40 million hectares of degraded pastures. Inoculation with Bradyrhizobium bacteria in integrated crop-livestock systems has reduced synthetic nitrogen use by 30 to 50 percent while restoring soil microbial activity measured by dehydrogenase enzyme assays (Embrapa, 2025). The programme contributed to Brazil sequestering an estimated 170 million tonnes of CO₂-equivalent between 2010 and 2025.

Commercial soil testing adoption. Biome Makers' BeCrop platform has processed over 3 million soil samples across 50 countries by 2025, generating the world's largest soil microbiome database. The platform's functional predictions correlate microbial community composition with crop performance, disease risk and nutrient cycling efficiency, enabling data-driven agronomic recommendations.

What Isn't Working

Standardisation gaps. There is no universally agreed protocol for soil microbiome sampling, DNA extraction or bioinformatic analysis. Different labs using different methods on the same soil sample can produce divergent results, making cross-study comparisons unreliable (Gibbons et al., 2024). This limits the development of regulatory thresholds and standardised KPIs.

Carbon permanence uncertainty. Soil carbon gains from improved management are reversible. A single deep ploughing event can release decades of accumulated organic carbon. Without long-term management commitments and robust MRV frameworks, soil carbon credits face integrity questions. The Integrity Council for the Voluntary Carbon Market (ICVCM) has flagged soil carbon as requiring enhanced permanence safeguards (ICVCM, 2025).

Inoculant inconsistency. Despite commercial enthusiasm, microbial inoculants frequently fail to establish in soils with competitive native communities, high temperatures or suboptimal pH. A 2024 review across 112 field trials found that 40 percent of commercial inoculant applications showed no statistically significant yield benefit (Kaminsky et al., 2024). Better strain matching and formulation technologies are needed.

Knowledge access barriers. Smallholder farmers in low-income countries, who manage approximately 80 percent of the world's farms, rarely have access to microbiome testing services, genomic data interpretation or tailored management recommendations. Extension services remain underfunded, and commercial platforms are priced for large-scale operations.

Pollution impacts. Pesticides, heavy metals and microplastics continue to degrade soil microbial communities. A 2025 European Environment Agency report found that 25 percent of European agricultural soils exceed safe thresholds for at least one contaminant, with fungicide use reducing mycorrhizal colonisation by up to 40 percent in treated fields (EEA, 2025).

Key Players

Established Leaders

• Biome Makers — World's largest soil microbiome analytics platform; 3M+ samples processed across 50 countries using its BeCrop technology.
• Indigo Agriculture — Offers microbial seed treatments and operates the Indigo Carbon programme linking soil health practices to carbon credit generation.
• Novozymes (now Novonesis) — Global leader in biological solutions; produces BioAg inoculants reaching 60M+ acres annually.
• Embrapa — Brazil's agricultural research corporation; pioneered large-scale Bradyrhizobium inoculation and integrated crop-livestock-forestry systems.

Emerging Startups

• Trace Genomics — AI-driven soil diagnostics platform providing pathogen risk and microbiome health assessments for precision agriculture.
• Yard Stick PBC — Combines ground-penetrating sensors with machine learning to measure soil carbon rapidly and affordably in the field.
• Pivot Bio — Engineers nitrogen-fixing microbes that colonise crop roots, reducing synthetic fertiliser dependency by up to 25 pounds N per acre.
• Loam Bio — Develops fungal seed coatings that enhance soil carbon sequestration, with field trials across Australia and North America.

Key Investors/Funders

• Breakthrough Energy Ventures — Bill Gates-backed fund; invested in Pivot Bio and other soil biology startups.
• The Rockefeller Foundation — Supports regenerative agriculture programmes and soil health research in sub-Saharan Africa and South Asia.
• European Commission Horizon Europe — Funds the European Soil Observatory and the Mission "A Soil Deal for Europe" with a budget exceeding €300 million.
• Cargill — Committed US$25 million to the Soil Health Partnership and regenerative agriculture supply chain programmes.

Sector-Specific KPI Benchmarks

Action Checklist

• Establish a soil health baseline across operational or supply-chain lands using microbiome sequencing, the Haney Test or Cornell CASH framework.
• Implement cover cropping in all arable rotations; target year-round living root cover to sustain rhizosphere microbial communities.
• Reduce tillage intensity progressively; transition to no-till or minimum-till where agronomically feasible.
• Apply compost, biochar or organic amendments at rates informed by soil test results to increase substrate availability for microbial communities.
• Evaluate microbial inoculants critically; request independent field trial data and assess compatibility with native soil conditions before large-scale adoption.
• Monitor soil organic carbon, microbial biomass and enzyme activity annually to track intervention impacts and adjust management.
• Integrate soil health metrics into sustainability reporting under TNFD, CSRD and national GBF action plans.
• Partner with research institutions or commercial platforms for ongoing microbiome data collection and interpretation.

FAQ

How long does it take to see measurable improvements in soil microbiome health? Most studies report detectable increases in microbial biomass and diversity within two to three growing seasons of implementing cover cropping and reduced tillage. Significant gains in soil organic carbon typically require five to ten years of consistent management. The timeline depends on starting conditions, climate, soil type and the intensity of interventions applied.

Can soil microbiome management replace synthetic fertilisers? Not entirely in most systems, but it can substantially reduce dependency. Nitrogen-fixing bacteria and mycorrhizal fungi improve nutrient availability, and trials consistently show 15 to 30 percent reductions in synthetic nitrogen application without yield loss. In legume-based systems with effective Rhizobium inoculation, nitrogen fertiliser use can approach zero. Phosphorus-solubilising microbes similarly reduce the need for phosphate inputs but rarely eliminate them.

What is the carbon sequestration potential of soil microbiome management? Global estimates range from 1.5 to 3.5 Gt CO₂ per year if best practices were adopted across all agricultural and degraded lands (Minasny et al., 2024). Realistic near-term potential is lower, given adoption barriers and permanence concerns. The "4 per 1000" target of 0.4 percent annual increase in soil organic carbon stocks would sequester approximately 2.4 Gt CO₂ per year if achieved globally, which would offset roughly 25 percent of annual fossil fuel emissions.

Are soil carbon credits credible? Credibility varies widely. High-integrity programmes require robust baselines, conservative estimates, regular monitoring and long-term management commitments. The ICVCM's Core Carbon Principles provide a quality benchmark. Buyers should look for credits with third-party verification, digital MRV support and buffer pools to address reversal risk. Permanence remains the primary concern, as soil carbon gains are reversible if management practices change.

How do microplastics affect soil microbiomes? Microplastics alter soil structure, water retention and microbial habitats. A growing body of research indicates that microplastic contamination reduces microbial diversity, disrupts nitrogen cycling enzymes and can shift community composition toward stress-tolerant taxa. Agricultural soils receiving plastic mulch or biosolids are particularly affected. The European Environment Agency (2025) flagged microplastics as an emerging soil contaminant requiring monitoring and regulatory attention.

Sources

• Global Soil Biodiversity Initiative. (2025). State of Knowledge of Soil Biodiversity: 2025 Report. GSBI and FAO.
• FAO. (2025). The State of the World's Soil Resources: 2025 Update. Food and Agriculture Organization of the United Nations.
• UNCCD. (2024). Global Land Outlook 2024: Land Degradation, Climate Change and Biodiversity. United Nations Convention to Combat Desertification.
• Minasny, B. et al. (2024). Soil Carbon Sequestration Potential Under Improved Management: Updated Global Estimates. Geoderma, 442, 116780.
• Tedersoo, L. et al. (2024). Global Patterns and Drivers of Mycorrhizal Symbiosis. Nature Reviews Microbiology, 22(5), 310-325.
• Lal, R. (2024). Soil Carbon Stocks and Fluxes: A 2024 Reassessment. Soil & Tillage Research, 240, 106050.
• Kallenbach, C. et al. (2025). Meta-analysis of Cover Cropping and Reduced Tillage Effects on Soil Microbial Biomass and Carbon. Agriculture, Ecosystems & Environment, 360, 108795.
• MarketsandMarkets. (2025). Agricultural Biologicals Market: Global Forecast to 2030. MarketsandMarkets Research.
• Kaminsky, L. et al. (2024). Efficacy of Commercial Microbial Inoculants Across 112 Field Trials: A Systematic Review. Applied Soil Ecology, 198, 105380.
• General Mills. (2025). Regenerative Agriculture Progress Report 2025. General Mills Inc.
• 4 per 1000 Initiative. (2025). Annual Progress Report: Soil Carbon Sequestration Across 80 Countries. 4 per 1000 Secretariat.
• Embrapa. (2025). ABC+ Plan: Results and Impacts of Low Carbon Agriculture in Brazil 2010-2025. Brazilian Agricultural Research Corporation.
• Gibbons, S. et al. (2024). Methodological Variability in Soil Microbiome Studies: Implications for Standardisation. ISME Journal, 18(3), 445-458.
• ICVCM. (2025). Assessment Framework for Soil Carbon Credits. Integrity Council for the Voluntary Carbon Market.
• EEA. (2025). Soil Contamination in European Agricultural Lands: Status and Trends. European Environment Agency.