If biodynamics is about soil fertility then soil fertility is about humus. Microbes are the bridge between the soil and the plant. When microbes, particularly fungi, are given the chance to completely digest organic matter, humus is formed. The humus colloid will hold both positive and negative nutrients preventing their loss via leaching. Humus holds up to 90% of its weight in water. Humus is the foundation for good soil structure.
“In Australia’s landscapes a 2% increase in humus to 20cm depth would equate to an increase in water holding capacity of approximately 30 litres per square metre or 1 Olympic pool per 10 hectares”.