Soil fertility and humus building the biodynamic way

Fertile soil is not the precondition of biodynamic agriculture but its actual goal. While conventional fertilisation mainly feeds the plant, the biodynamic method aims at the soil itself: it should become alive, build humus and carry the plant from its own strength. This article explains how that works — through the cycle, compost management and the preparations — and separates what is proven from what is tradition.

Why humus is the core

Humus is the organic, lastingly transformed part of the soil, formed from decomposed plant and animal remains. It is more than a nutrient store: humus improves crumb structure, holds water, promotes aeration and is the habitat for the soil life that makes nutrients available to plants in the first place. A humus-rich soil is therefore more resistant to drought and erosion — a decisive advantage in a climate with more frequent weather extremes.

Soil degradation is a real problem: according to the FAO's assessment, a considerable proportion of the world's soils has already been damaged in its fertility. Building humus is therefore not only a question of yield, but of the long-term viability of a farm.

The biodynamic approach: bringing the soil to life

In the Agriculture Course, Rudolf Steiner described good fertilisation as "enlivening the earth": the soil should be brought to life so that the root does not reach into "dead earth". From this follows the biodynamic way of working with the soil, which rests on a few pillars.

At the centre is the farm organism — the cycle, as closed as possible, in which feed, manure and compost stay on the farm and fertility comes from the farm's own system rather than from bought-in fertiliser. Compost management refines farmyard manure into stable humus; the compost preparations guide the decomposition. Horn manure enlivens the soil and promotes root penetration. On top of this come the familiar building blocks of good soil practice that also apply outside biodynamics: permanent soil cover through mulch and catch crops, gentle cultivation with little turning of the soil, diverse crop rotations and deep-rooting plants that bring organic matter down into the depths.

What is proven — and what is tradition

Here an honest distinction is worthwhile. That a living circular economy with good compost care builds up the soil is measurable: FiBL's DOK long-term trial (running since 1978) attributes the highest soil fertility to the biodynamic system — around 16 per cent higher humus contents and up to 83 per cent higher activity of soil organisms than in the conventional system. That is a robust finding, not a matter of belief.

The specific effect of the individual preparations in high dilution, on the other hand, is harder to isolate and remains scientifically disputed; there are indications, but no conclusive proof. A fair reading: the main share of humus building is carried by the cycle and compost management, and the preparations add impulses on top. More on this under Biodynamics and science.

What this means in practice

For building soil fertility, the same basic recipe applies in biodynamic and regenerative farming alike: add organic matter and keep it in the soil, keep the soil covered and rooted, cultivate gently and feed the soil life instead of disturbing it. The biodynamic method adds the cycle concept of the farm organism and the work with the preparations. The reward does not show overnight but over years — visible, for example, in a spade diagnosis, in deeper rooting and finer crumb structure.

Frequently asked questions

How do you build humus in the soil?

By adding and keeping organic matter: compost and farmyard manure, permanent soil cover (mulch, catch crops), gentle cultivation and diverse crop rotations. In biodynamics, the circular economy and the preparations are added.

Is biodynamic humus building scientifically proven?

For the system as a whole, yes — the DOK trial shows higher humus contents and soil activity. The specific contribution of the individual preparations is harder to demonstrate.

What distinguishes biodynamic from "regenerative"?

The soil practices overlap strongly. Biodynamics adds the closed farm organism with livestock and the mandatory work with the preparations.