Living soil

In a salt-fed system you supply plant-available nutrients directly in the irrigation water. The substrate is inert or close to it; you are the nutrient source, and the plant eats what you give it that day.

In living soil the nutrients are present as organic matter and slowly available minerals, and a population of bacteria, fungi, protozoa and other organisms mineralises them over time. You feed the soil, the soil feeds the plant. The consequence is that the system has momentum in both directions: it will not run out because you missed a feed, and it will not respond quickly when something is wrong.

A useful mental model is that you are managing a nutrient stock rather than a nutrient flow. Corrections happen on a scale of weeks, not hours.

The common construction is roughly equal parts of three things, then amended with minerals.

• —A base for structure and water holding: peat or coco.
• —An aeration fraction: pumice, lava rock, rice hulls or perlite. This keeps the soil from compacting once it is biologically active and being watered heavily.
• —Compost or worm castings, which carry the biology and a share of the nutrition. This is the component whose quality most affects the result, and quality varies enormously.
• —Mineral and organic amendments mixed through the whole volume: rock dusts, gypsum, agricultural lime for calcium and pH buffering, and slower organic inputs such as kelp, alfalfa, neem or crustacean meals.

NoteA fresh mix is usually cycled before planting, kept moist and warm for several weeks so the biology establishes and raw amendments begin to break down. Planting into a hot fresh mix is a common way to burn seedlings.

The maintenance model is to return what the crop removed, at the surface, and let the biology move it down. In practice that means top dressing with amendments and compost between cycles, keeping a mulch layer so the soil surface stays moist and biologically active, and in larger beds growing a cover crop such as clover between runs.

Reuse is the point. A well-maintained bed improves over several cycles as organic matter accumulates and the biology matures, and the running cost after the initial build is low. This is the strongest practical argument for the method and it holds up well.

Compost teas deserve an honest note. Brewing aerated compost tea and applying it as a soil drench is near-universal in this community. The agricultural research literature on compost tea efficacy is mixed at best, with many trials showing no measurable benefit and considerable variability in what a brew actually contains. Applying good compost directly is better supported than applying a tea made from it. If you brew tea and like the results, that is fine; it is not a settled practice.

Water quality matters more here than in a salt system, because chlorine and especially chloramine are added to municipal water specifically to kill microorganisms. Chlorine dissipates if water stands; chloramine is stable and does not, and requires filtration or treatment to remove. This is one of the few genuinely non-negotiable details.

Container volume matters because the nutrient stock is proportional to the soil volume. Small pots of living soil run out and have to be fed liquid amendments, at which point much of the advantage is gone. Larger volumes, or beds, are where the method works as intended.

There is also no need to water to runoff. In a salt system, runoff flushes accumulated salts. In living soil there is nothing to flush and runoff removes nutrition and soluble organic matter that you paid for. Water to field capacity and stop.

The honest comparison is a set of trade-offs, not a winner.

Living soil is forgiving, cheap to run once built, reusable, and requires no reservoir management or pH adjustment in the usual case. It is also slow to correct, harder to diagnose because a visible deficiency means a problem that started weeks ago, heavier to move, and space-hungry.

Salt feeding is precise, fast to correct, and steerable, which is why commercial production uses it. It also demands attention: a failed pump, a drifted reservoir or a miscalculated EC shows up in the plant within a day.

Yield claims in either direction should be treated carefully. There is no good controlled evidence that either method systematically outperforms the other on yield in the hands of a competent grower. What is well established is that the two methods fail differently, and choosing between them is largely a question of which failure mode suits your circumstances.

Guide: the precision alternative

Two are worth naming directly, because they are repeated constantly.

The first is that living soil raises cannabinoid potency. There is no good evidence for this. Potency is overwhelmingly genetic, with environment affecting how close a plant gets to its ceiling. Nothing about organic nutrient cycling has been shown to raise that ceiling.

The second is that organically grown cannabis tastes better. Taste preferences are real and widely reported, and there are plausible mechanisms involving how a plant finishes and how it is dried. But the comparisons behind the claim are almost never controlled, and the same growers who use living soil also tend to dry slowly and handle material carefully, which are known to affect flavour on their own. The claim may be true; it has not been demonstrated.

A grower who likes the method does not need either claim to be true. Low input cost, reuse and forgiveness are sufficient reasons on their own.

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