Increasing Soil Carbon with Compost, Mulch, and Deep Roots
Soil carbon is the foundation of a thriving regenerative garden. Higher carbon levels improve fertility, water retention, and microbial activity, while also helping fight climate change. By using compost, applying mulch, and planting deep-rooted crops, gardeners can naturally build soil carbon over time.
Soil carbon is the carbon stored in the soil as organic matter—things like decomposed leaves, roots, compost, and the remains of soil organisms. It’s the foundation of healthy soil because it fuels microbial life, improves structure, and helps soil hold water and nutrients. Plants play a key role in creating soil carbon: through photosynthesis, they pull carbon dioxide from the air and send some of that carbon down to their roots, where it becomes part of the soil food web. The more soil carbon you build, the richer and more resilient your garden becomes, supporting both plant health and long-term soil regeneration.
Decades of hands-on gardening have shown me that small, consistent practices—layering compost, keeping the soil covered, and growing plants with strong root systems—produce resilient, carbon-rich soil that supports healthy vegetables, fruits, and herbs.
How Compost Builds Soil Carbon
- Adds Organic Matter: Decomposed plant material introduces carbon into the soil.
- Feeds Microbes: Soil microbes use carbon as energy, creating humus that stores nutrients.
- Improves Structure: Compost increases water retention and aggregation, locking carbon in soil.
Tips: Use a mix of kitchen scraps, garden clippings, and aged manure; apply as topdress or incorporate lightly.
How Mulch Supports Carbon Storage
- Protects Soil: Reduces erosion and prevents carbon loss from sunlight exposure.
- Feeds Soil Life: Organic mulch decomposes slowly, adding carbon to the soil.
- Suppresses Weeds: Less competition allows crops to thrive and build root biomass.
Tips: Use leaves, straw, grass clippings, or wood chips. Keep a 2–4 inch layer and replenish as needed.
Deep-Rooted Plants: Carbon Capturers
- Roots Transfer Carbon Below Ground: Plants like comfrey, daikon radish, and perennials store carbon in deeper soil layers.
- Improve Soil Structure: Root channels enhance aeration, water infiltration, and microbial activity.
- Increase Biomass: Both above-ground and below-ground plant parts contribute carbon when they decompose.
Tips: Include a mix of deep-rooted perennials, root crops, and cover crops for maximum effect.
Cheat Sheet: Build Soil Carbon
| Practice | How It Increases Carbon | Quick Tips |
| Compost | Adds organic matter & feeds microbes | Topdress or lightly incorporate |
| Mulch | Protects soil & slowly decomposes | Use 2–4 inch layers of organic material |
| Deep-Rooted Plants | Transfers carbon deep, builds biomass | Plant perennials, root crops, and cover crops |
| Cover Crops | Roots & foliage add carbon | Rotate legumes, grasses, and flowering plants |
| Minimal Tillage | Keeps carbon in soil | Avoid deep plowing; use broadforks or no-till methods |
Tips from My Garden
I layer compost in spring, mulch beds with leaves and straw, and interplant deep-rooted radishes with clover. Over time, my raised beds are darker, more crumbly, and teem with worms—clear signs that carbon is building and the soil is thriving.
Conclusion
Building soil carbon with compost, mulch, and deep roots is a simple, effective strategy for regenerative gardening. By feeding soil life and protecting your beds, you create resilient, productive soil that nurtures plants, stores carbon, and supports a healthy ecosystem.
Soil Carbon Boosting Cheat Sheet: Compost, Mulch & Deep Roots
Why Build Soil Carbon
- Improves fertility and water retention
- Feeds beneficial microbes
- Enhances soil structure and resilience
- Stores carbon to help combat climate change
Key Practices
| Practice | How It Boosts Carbon | Quick Tips |
| Compost | Adds organic matter & feeds microbes | Topdress or lightly incorporate; use kitchen scraps, garden clippings, aged manure |
| Mulch | Protects soil & slowly decomposes | Apply 2–4 inch layers of leaves, straw, grass clippings, or wood chips; replenish regularly |
| Deep-Rooted Plants | Transfers carbon deep into soil & builds biomass | Plant perennials, root crops (daikon radish), and cover crops |
| Cover Crops | Roots & foliage add carbon, support microbes | Rotate legumes, grasses, and flowering plants for diversity |
| Minimal Tillage | Reduces carbon loss from disturbance | Avoid deep plowing; use broadforks or no-till methods |
Tips from the Garden
- Layer compost in spring and mulch beds consistently.
- Interplant deep-rooted crops with vegetables for year-round carbon capture.
- Observe soil color, crumb structure, and worm activity as indicators of soil health.
- Combine multiple practices for maximum carbon storage and soil regeneration
Regenerative Gardening Learning Hub
🌿 Start here: The Complete Guide to Regenerative Gardening and Farming
1️⃣ Soil Health and Living Systems
- How to Build Living Soil: A Step-by-Step Guide
- Understanding the Soil Food Web: Life Beneath Our Feet
- How to Use Compost and Vermicompost in a Regenerative Garden
- Mulching for Soil Health: How to Protect and Feed the Soil Naturally
- Using Mycorrhizal Fungi to Boost Plant Health and Yield
- Minimal Tillage: Why and How to Disturb the Soil Less
- How to Test, Read, and Rebalance Your Soil Naturally
2️⃣ Biodiversity and Polyculture
- How to Design Polycultures and Companion Plantings for Regenerative Gardens
- Integrating Native Plants into Your Food Garden
- Creating Habitat for Beneficial Insects and Pollinators
- Cover Cropping for Biodiversity and Soil Regeneration
- Crop Rotation for Soil Fertility and Pest Management
3️⃣ Carbon Sequestration and Organic Matter
- Why Capturing Carbon in the Garden Is Important and Fights Climate Change
- Increasing Soil Carbon with Compost, Mulch, and Deep Roots
- Biochar: What It Is and How to Use It in the Garden
- How to Keep Soil Covered Year-Round to Build Carbon and Fertility
4️⃣ Water Stewardship
- How to Use Water Wisely: The Principles of Water-Wise Regenerative Gardening
- Building Swales and Contour Beds to Slow and Sink Rainwater
- Mulch, Groundcovers, and Soil Structure for Water Retention
- Harvesting Rainwater for Regenerative Gardens
5️⃣ Perennial Crops and Permanent Systems
- How to Transition from Annuals to Perennials in the Vegetable Garden
- Perennial Vegetables for Regenerative Systems
- Agroforestry and Food Forest Basics for Gardeners
- Integrating Fruit Trees and Shrubs into the Vegetable Garden
6️⃣ Animal Integration
- Chickens in the Garden: How to Use Them Regeneratively
- Using Worms and Bees as Regenerative Allies
- The Role of Animals in Closing the Nutrient Loop
7️⃣ Human and Community Connection
- The Ethics of Regenerative Gardening: Care for Earth, People, and Future Generations
- How to Build a Community Garden Using Regenerative Principles
- Teaching Regenerative Gardening to Children and Beginners
- Healing the Land and Ourselves: The Psychology of Regenerative Practice
8️⃣ Regenerative Design and Planning
- How to Plan a Regenerative Garden from the Ground Up
- Regenerative Gardening Principles Simplified for the Home Gardener
- Home Garden Permaculture
- How to Create a Home Food Forest
- French Intensive Gardening
- Square Foot Gardening
- Zone and Sector Planning for Small Regenerative Gardens
- Using Observation and Feedback to Improve Your System Each Season
9️⃣ Inputs and Outputs: Closing the Loop
- How to Make and Use Compost Tea and Fermented Plant Extracts
- Zero Waste Gardening: How to Cycle Nutrients and Minimize Inputs
- How to Build a Closed-Loop Garden System
10️⃣ Case Studies and Personal Experience
