Organic Soils

sun prairie organic logoThe most important resource for any farmer – and especially for an organic farmer- is the soil. The soil is a complex community of living creatures whose interaction provides food for plants and animals. Thus, our life depends on the functioning of the soil life. Once life in the soil is extinct, so are plants, animals and people.

Organic Soil
Organic Soil

Most of the life in the soil is invisible to our eye. It consists of microscopic organisms such as bacteria, fungi, protozoa, nematodes, micro-arthropods and some larger organisms such as earthworms. Did you know that there are more organisms in a single spadeful of rich garden soil than above-ground in the entire Amazon rain forest? In just one gram, or about 1 teaspoon, of healthy agricultural soil we find several million micro-organisms. The healthier the soil ecosystem, the higher the number and the greater the diversity of species.

Soil organisms are involved in the following processes vital to us:

  • nutrient retention and cycling (less or no fertilizer needed)
  • decomposition of plant residues and formation of humus.
  • disease suppression (beneficial organisms prevent access of pathogens to plants)
  • building of granular soil structure (makes the soil sponge-like; helps to hold more water)
  • break-down of contaminants such as pesticides or oil spills

Pesticides have been shown to harm the diversity of soil life by killing non-target organisms. Dr. E. Ingham, soil ecologist at Oregon State University, explains that the herbicide atrazine is a better bactericide than herbicide. Bacteria are the main organism contributing to nitrogen retention in the soil. If they are killed, soil looses the ability to hold nitrogen fertilizer which instead migrates into the ground water.

Alcohol-based pesticides such as 2,4-D were found to kill non-target beneficial nematodes. These types of nematodes consume bacteria and, in the process, release nitrogen to plants. This in turn reduces the need for fertilizer. After no more pesticides are used it may take years before beneficial nematodes return.

For more information on life in the soil, visit Dr. Ingham’s website

I am now aware of these delicate ecosystem interactions. It is important to work diligently towards balancing the soil food web; and towards reviving a healthy diversity of soil life.