Push the zoom button on your soil and you will see a bag full of sticky strings, soil particles, plant leftovers and organic matter, says Kris Nichols, soil microbiologist with USDA-ARS Northern Great Plains Research Laboratory, Mandan, N.D. The strings are crop roots and fungal hyphae, or bodies, coated with glue snagging soil particles into aggregates, clods or pellets. They are the bag.

The finer the roots, the more efficient they are at grabbing nutrients, while requiring less valuable carbon as fuel. They are lean, high-mpg soil workhorses. Piggybacking on them are friendly fungi, arbuscular mycorrhizae, which unlock chemical bonds to release phosphorus (P), sulfur, nitrogen (N) and micronutrients into forms that crops can use. These fungi can take up soil P up to six times faster than the root hairs.

Nutrients made available through biological processes are absorbed and metabolized more easily and efficiently than synthetic fertilizers, says Jill Clapperton, rhizosphere (root zone) ecologist and president of Rhizoterra, Lolo, Mont.  “Soil biological processes are responsible for about 75% of the available N and 65% of the available P in the soil.  Practices like crop rotation and tillage affect the number, diversity and functioning of the micro- and larger organisms in the soil community, which in turn affect the nutrient content of the crops we grow,” she says.