Organic matter ‘holds nutrients for plants in an accessible form, holds water in the soil and makes the soil friable. This is the foundation for healthy plant growth and development,’ (Timothy Brink, 2018, p.26). Hence those striving for sustainable soils focus on the retention of organic matter for many reasons, says New Zealand organic and Biodynamic consultant Bart Arnst who has this to say:

  • Both living and humic material help bind soil particles to form aggregates which in turn improves soil structure leading to better drainage and water holding capacity particularly in fine textured soils.
  • Organic matter will increase the number of water stable aggregates and decrease soil erosion. The humic materials have high surface areas which retain more water. Living organisms are 90% water so organic matter will increase the soil’s capacity to hold moisture. Soil organic matter is mostly insoluble in water which makes it difficult to be leached from the soil.
  • Organic matter acts as a source and sink for plant nutrients, reacts with metal cations to form stable complexes. Metals Al and Fe are held strongly. So the soil organic matter will reduce the toxic levels in soil water allowing plant root growth.
  • Organic matter is one of the main components of soil which control the pH buffering capacity of soils.
  • Micro-organisms in the organic matter help recycle nutrients held in plant and animal residues. They will also convert organic form into plant available inorganic form, decompose organic residues and degrade pesticide residues.
  • Organic matter will absorb organic pesticides and thereby reduce ground water pollution.


Timothy Brink, ‘Convert your farm to Biodynamics’, Star and Furrow (Journal of the Biodynamic Association UK), No. 120 December 2013, p.25-28