Organic Home Gardening with Living Soil
Living soil is an organic gardening method that uses a nutrient-rich potting mix teeming with beneficial microbes to grow plants instead of mineral fertilizers. It aims to create a sustainable mini-ecosystem in the soil, modeled after the natural processes found in nature. Everest Fernandez discusses how growers can transition from soilless potting mixes to organic living soil.
Living soil is all about nurturing soil life. The central goal is establishing a nutritionally balanced soil mix teeming with beneficial bacteria, fungi, protozoa, and more. These microbes form symbiotic relationships with plant roots, helping them absorb nutrients effectively; they break down organic matter and mineralize nutrients into plant-available forms, recycling nutrition.
Living soil can be reused from one crop to the next—nothing to compost and nothing for the landfill. Of course, for optimal results over several crops, the nutrition and overall health of the soil must be monitored and maintained.
Different Approaches
Some living soil practitioners prefer to amend their soils upfront—think “living super soil”—and irrigate with water only through to harvest. Other growers prefer a lighter starting mix to retain the control of choosing when to supplement with targeted and tailored top-dressed nutrition. In either case, it’s essential to understand the soil’s dynamic ecosystem and its effect on plant health. A thriving microbial life is a cornerstone of a robust living soil system.
Support from Indoor Gardening Stores
Some early hype about living soil could have scared some stores from stocking it! After all, what store owner in their right mind would sell their customers a bag of “magic soil” that lasted forever and freed them from ever buying a bottle of mineral nutrients again? The reality is that living soil growers require a regular influx of sundries such as water purification products, powdered organic inputs, high-quality compost, bio-stimulants, mycorrhizae, and more. Some stores are further along the curve than others when it comes to catering to living soil growers.
Living soil blenders, like mineral nutrient formulators, pay close attention to the ratios of cations (ammonium, calcium, magnesium, potassium, and sodium) with the appropriate amount of total nitrogen for the intended use (higher N for water only and lower for a ‘light mix’). Over time, these minerals will become depleted in the soil. Increasingly, indoor gardening stores offer a range of specialist organic inputs that can help restore specific minerals or mineral groups to more optimal levels. See the table: Common Amendments Used to Rejuvenate Living Soils.
Maintaining Microbial Life in Living Soil
Establishing the proper nutritional balance in the soil is just the beginning. Growers also need to ensure that microbial life is present in all its forms so that these nutrients are sufficiently available to plants. If microbial life is lacking, growers must use additional inoculants and compost extracts. Products used to boost beneficial biology in soil include beneficial bacteria powders and liquids (Bacillus methylotrophicus, Bacillus subtilis, and Bacillus licheniformis), fungi (Trichoderma), enzymes, amino acids, kelp powder and extracts, hydrolyzed fish proteins, and insect frass.
Different microbes play specialized roles. Bacteria decompose organic materials into simpler compounds, mycorrhizal fungi draw in water and nutrients via their threadlike hyphae, while protozoa graze on bacteria to mineralize nutrients. This intricate web of microorganisms creates a sustainable and efficient nutrient cycle within the soil.
Follow the 5 – 10% Rule
Most living soil beginners overwater their plants. It’s easiest to commit this mistake when transplanting into final-stage pots. Living soil requires minimal initial watering. Many living soil growers use “the 5 – 10% rule” to help them. Early on, they only water 5% of the pot volume. So, for a 20-gallon pot, the recommendation of 5% would be to water just one gallon—water only around the plant at first. After establishment, growers can progress to keeping the entire surface moist (still using the 5% rule). When plants are firmly established, growers can increase watering to 10% to mitigate the risk of the lower layers of soil drying out.
Remember, don’t treat living soil like coco coir and water until you get 30% run-off! Creating leachate will completely over-saturate your soil and rinse away some of the valuable nutrition it holds.
Living Soil Needs Large Fabric Containers
Large fabric pots are the most convenient for many indoor growers, providing excellent aeration to the roots. Be sure to get the size right. Think about the volume of fabric pot you might use for a large plant in a soilless mix and then double it for living soil. Generally, growers should allocate 60 to 120 gallons of living soil mix per 4′ x 4′ of canopy. So, if you’re growing four plants in a 4′ x 4′, that’s 15 to 30 gallons per plant as a minimum.
US-based living soil growers, in particular, favor a larger volume of soil. Thirty gallons would be considered a minimum rather than an upper limit! Larger volume containers facilitate a more extensive root system and better moisture retention.
The less soil you use, the harder it will be to keep your plants happy without resorting to liquid feeds. However, one issue that growers should be aware of is the tendency of living soil near the sides of fabric pots to dry out more, making life more difficult for beneficial biology at these physical fringes. Growers must pay close attention to even watering and consider insulating the sides of pots to maintain consistent soil moisture and temperature.
Living Soil Works Best in Beds
If you want to raise your growing game a few notches, consider constructing or purchasing a living soil bed to accommodate multiple plants. Gareth Griffin, the new World Record Holder for heaviest onion, grew his 19-pound (nearly 9 kg) beast in a living soil bed. This incredible feat was achieved using only organic cultivation techniques, causing many growers worldwide to start paying attention.
Sacramento-based living soil enthusiasts, Grassroots, offer specially adapted fabric soil beds that mitigate moisture loss through the sides. They recently collaborated with BuildASoil in the US and Ecothrive in the UK to offer living soil beds to a wider market, including an automated living soil system using Autopot’s Tray2Grow wicking system. Beds offer the advantage of fostering a ‘community root system,’ which can lead to significantly improved plant health and yield. When growing in beds, growers can go to town with allocated soil volume, and the plants benefit from an interconnected root system rather than being isolated in their container.
Rejuvenating and Re-Using Living Soil
Beds simplify rejuvenating and maintaining the soil, making it easier to add amendments and manage the soil ecosystem. Some growers create different layers within the beds, the most common practice being a bottom layer of fast-draining, high-porosity material, like perlite.
It’s a lot easier to reuse living soil when using beds. Commercial living soil growers typically veg their plants in two or three-gallon fabric pots with the bottoms cut out. At transplant time, the plant is not removed from the pot but lifted and re-positioned directly on the living soil bed. This means you lose potential head height, but vertical space is less commonly an issue for commercial growers. When transplanted, the lower roots enjoy access to the living soil below. At harvest time, growers can take the super low-labor option and cut plants at their base, leaving the remaining roots to be reintegrated into the living soil—typically via the addition of enzyme products that aid in the breakdown of the roots. However, more living soil growers are adopting the practice of cutting out root balls and replacing them with fresh living soil mix to mitigate the risk of propagating root-borne diseases between crops.
Good Practices with Living Soil
Living soils are typically based around sphagnum peat moss or coco coir—both serve as a moisture reservoir for the soil and are critical for fast-growing, demanding plants. Compost and organic fertilizers like alfalfa, bone meal, kelp meal, feather meal, and rock minerals provide balanced, slow-release nutrition for microbes. Worm castings inoculate beneficial species, while bio-stimulants like insect frass can introduce microbial diversity.
Irrigating with water will suffice for most of the plant lifecycle, but some hungrier species will likely require supplementation. Be sure to use dechlorinated water so the soil microbiology can thrive. Organic liquid feeds can be used sparingly if needed, but scratching in some top dressing with organic powder amendments mixed with high-quality compost is the best way to ensure longer-term nutrition. Indoor gardening stores looking to serve living soil growers should be mindful of stocking various quality organic inputs to help cultivators replenish their soils.
Don’t forget to test your soil regularly—at least at the end of a growing cycle so you know which amendments you should be reaching for. Logan Laboratories in Ohio offers specialist soil analysis services that provide the necessary detail to amend your living soil efficiently and effectively. Commercial living soil growers will give their soil analysis to a specialist soil consultant, who advises on which amendments to add. While trace minerals are typically the first to dip to sub-optimal levels, nitrogen is the hardest (and most important) to maintain due to its volatility and high demand, followed by Ca, Mg, P, and K.
A Final Word on Crop Quality?
No discussion about living soil would be complete without a mention of crop quality. Maybe you’re happy with the results from soilless, Grow A & B, Bloom A & B, and liquid Hocus-Pocus—but the crop quality produced by living soil gardens is really turning heads. Denser flowers, vivid colors, more sophisticated terpene profiles, higher potency, and longer shelf-life are just a few of the talking points. As such, the best living soil-grown produce is often in high demand.
Common Amendments Used to Rejuvenate Living Soils
| N, P, K, Calcium, and other micronutrients | |
| Micronutrients, particularly silica | |
| High in N, P, and micronutrients | |
| High N, some micronutrients | |
| P, Calcium | |
| Calcium, helps in pH adjustment | |
| N, P, K, and micronutrients | |
| High in N | |
| P, Calcium | |
| Calcium, Sulfur | |
| Varies with crop type, generally N, P, K | |
| N, P, K, and chitin | |
| N, P, K (similar to Neem meal) | |
|
Magnesium, Sulfur |
| P, K, micronutrients, and growth hormones | |
| N, P, K, and other micronutrients | |
| Balanced N, P, K, and micronutrients | |
| N, P, K and micronutrients | |
|
Calcium, Silica, and other trace minerals |
