The Soil Jungle Beneath Your Feet

Photo by NRCS Soil Health. Soil Health: Soybeans Planted into Winter Wheat Stubble photo (CC BY 2.0)

Written by Roy Neilson, James Hutton Institute

The next time you walk into the garden, take a moment and tread very carefully across the soil.

You are walking on top of arguably one of the most diverse habitats on earth. Soil is a jungle, with forests of fungal hyphae interspersed with bacteria and watering holes located between the soil particles. Creatures roam, moving over and between the soil particles, riding the wave of the water table scooping up plant material, predating on each other, reproducing (they make bunnies look lazy!!) and pooping highly nutritious material for plants to take up and produce crops.

Since you are in the garden, bend down and pick up approximately one teaspoon of soil. You are now holding in your hands a wonderful diversity of living matter and numerically more living organisms than there are humans on the planet. Soil is teeming with wildlife that come in all shapes and sizes from the iconic earthworm (Fig. 1) to microscopic nematodes (Fig. 2), protozoa, bacteria and viruses, just to name a few (there are many more soil animals) and they drive all the major soil processes.

Figure 1. Lumbricus terrestris known as the “common earthworm”. An anecic species that forms deep burrows and comes to the soil surface to feed.

Figure 1

If the soil is healthy and depending on the soil texture (sandy, clay or loam), in one gram of soil you are likely to be holding up to 1 Billion (yes, really!!) bacteria; 100,000 protists; 100s of nematodes, 1 earthworm, metres of fungal hyphae and many more bugs and beasties.

Figure 2. Anatonchus tridentatus, a predatory nematode (left), feeding on an unsuspecting juvenile omnivorous nematode.

Figure 2

Each and every soil animal has a role to play whether it be beneficial, for example, by releasing nutrients from organic matter to be taken up by plants or detrimental such as causing crop disease. We simply are unable to live without these creatures as they contribute to many soil services that we take for granted (e.g. food production, landscape drainage). Yet pressures on soil and its plethora of animals is increasing through a changing climate, intensification of agricultural production and urbanisation. Consequently, global soil erosion has increased with an associated loss of organic matter, the fuel for these soil animals, contributing to reduced soil fertility and stagnating crop yields. It is only in recent years with the onset of new DNA-based technologies that researchers have been able to begin to untangle the complex relationships and roles of soil animals leading to a better understanding of the crucial role they play to support the very foundation of life.

So the next time you walk into the garden, take a moment, tread very carefully across the soil and be amazed at the world beneath your feet.