Proceedings 2006

Indiana Certified Crop Adviser Conference

The Real Dirt: Soil as a Habitat

Soil is much more interesting than dirt! You’ll see in this presentation that “when we are standing on the ground, we are really standing on the roof top of another world”. Living in the soil are plant roots, viruses, bacteria, fungi, algae, protozoa, mites, nematodes, worms, ants, maggots and other insects and insect larvae (grubs), and larger animals. Did you know that the number of living organisms below ground (known as soil biota) is often far greater than that above ground? Together with climate, these organisms are responsible for the decay of organic matter and cycling of both macro- and micro-nutrients back into forms that plants can use. Soil biota effect soil fertility and hence the primary productivity of the ecosystem that they inhabit, soil biological processes are responsible for approximately 75 percent of the available N and 65 percent of the available P in the soil. Plants can take-up and use nutrients made available through biological processes more easily and efficiently compared with chemical fertilisers. Microorganisms like fungi and bacteria use the carbon, nitrogen, and other nutrients in organic matter, while microscopic soil animals like protozoa, amoebae, nematodes, and mites feed on the organic matter, fungi, bacteria, and each other. These activities stabilise soil aggregates building a better soil habitat and improving soil structure, tilth and productivity. In agriculture, we modify the soil habitat with tillage and crop rotation practices and so influence the ability of the soil ecosystem to provide essential services such as decomposition and nutrient cycling. Agricultural practices such as crop rotations and tillage affect the numbers, diversity, and functioning of the soil biota, which in turn affects the establishment, growth, and nutrient content of the crops we grow. For example, including perennial forages, or to a lesser extent annual forages, in the rotation can enhance soil structural stability, increase soil organic matter - to depth, and increase the number, diversity and activity of most soil organisms. More importantly, our research has shown that including forages or forage mixtures as cover crops, increases the concentrations of micronutrients and P and Ca in the grain of the following crops. So let me introduce you to some of the organisms that live in the soil, and how they affect the cycling and availability of nutrients to crops, disease cycles, weed management, and soil. More detailed examples with mycorrhizal fungi and earthworms will demonstrate the important role of soil biology in improving soil quality and productivity. I’ll conclude with a discussion of how we can manage soil biological fertility so we get more for less.

Dr. Jill Clapperton is the Rhizosphere Ecologist at the Agriculture and Agri-Food Canada Lethbridge Research Centre in Lethbridge, Alberta, Canada. She is an internationally respected lecturer presenting research findings and promoting an understanding of how soil biology and ecology interact with cropping and soil management systems to facilitate long-term soil health and productivity. Her more specific research interests include plant-disease-soil nematode interactions, crop variety-nutrient uptake-rhizosphere community interactions, and soil organic matter quality influences on the diversity and populations dynamics of soil fauna. All the research in the Rhizosphere Ecology Research Group is aimed at understanding how soils function biologically so we can more effectively manage and exploit the long-term biological fertility of our soil. Jill has a keen interest in promoting science in schools and participates with other researchers and educators to develop soil ecology educational programs. The Worm Watch program (www.wormwatch.ca) that she initiated, has been consistently recognized by the National Science Teachers Association for excellence in science education. In 2000, Dr. Clapperton received the Patricia Roberts-Pichette Award from Environment Canada for enthusiastic leadership and commitment to advancing ecological monitoring and research in Canada.