Published by Chris Ellery at Soil Foodweb Institute, Soil Rehab Specialists since 1986
Reduce Erosion and Nutrient Leaching
The organic substances produced by biological nutrient cycling (e.g., clay and humus) have an ionic charge that holds nutrients in soil. When there is little organic matter in soil, nutrients are easily leached out by rapidly moving water. Biological exudates also create the adhesive effect that strengthens soil aggregates, improving structure so that soil is not easily broken down by water and blown away by wind.
Conserve Water: Increase Water Holding Capacity
Soil biology can increase a field’s water-holding capacity by adjusting the chemistry and physical properties of a soil. As the organisms consume and excrete organic matter, they produce the substances that glue soil particles together. Adding organic matter, and the biology to process it, changes the chemistry of the soil to increase the clay content. Because clay particles are magnitudes smaller than sand particles, the spaces between them are smaller as well. When water is caught in smaller pore spaces, it is less likely to drain out because it is held by the forces of adhesion. Building soil to increase water-holding capacity saves money on irrigation and
prevents leaching of nutrients.
Remediate Physical Properties: Improve Drainage, Build Structure
When compaction and poor drainage is a problem in your soil, improved tilth can be achieved by encouraging the proper soil biology. Fungi, insects and worms move through soil, creating macro-pores (air-filled spaces 50mm or larger) throughout and often deeper than the root zone of the plants. These macro-pores are the channels through which water can drain out. They also create space for plant roots to move in the soil, decreasing compaction. The conventional approach of intensive tilling to loosen compacted soil actually creates a hard pan beneath the tilled layer that impedes root penetration and can become anaerobic (attracting pathogenic bacteria). These tilling techniques also destroy fungal colonies that naturally aerate the soil. Soil Food Web advocates conservation tilling methods that reduce impact on soil biology and prevent the formation of hard pans.
Adjust Soil Structure and Hydrology
Loam soil, which is an even mixture of sand, silt and clay, is considered to be the best soil texture in which to grow crop plants. This is because the even mixture of different particle sizes creates an even mixture of pore (air/water-filled spaces in soil) spaces. Small pore spaces (called micro-pores) hold water by the forces of adhesion so that it stays in soil and is available to plants. Large pores (called macro-pores) allow water to drain out of the soil so that air can move through, providing oxygen that keeps the soil respiring aerobically. It is important to have a good mixture of macro/micro pores so that your soil holds water but does not get water-logged to the point of anaerobic respiration. The application and support of soil biology creates the diversity in texture necessary for healthy soil and easy plant cultivation.
*Ref. From an email sent by Christopher Ellery, Soil Foodweb Institute, 1 Crawford Road, Lismore 2480, Australia