The Soil is Alivel

Mark S. Coyne Professor of Soil Microbiology Department of Plant and Soil Science University of Kentucky

'Essentially, all life depends upon the soil ... There can be no life without soil and no soil without life; they have evolved together.'

Charles E. Kellogg, USDA Yearbook of Agriculture, 1938. "It is to the microorganisms of the soil that the human race owes its existence. If the unseen and lowly soil microorganisms cease functioning, plants would not grow, empires and republics, old order and new order, would fall to dust and proud Homo sapiens would pass out of existence." Martin Frobisher, Jr., Fundamentals of Soil Microbiology, 1953

Introduction

Grab a handful of soil. . . . . What does it look like? What does it feel like? It may seem rather ordinary; but look closer. What are you holding in your hand? A mixture of minerals and air with some water and organic matter? Is that all? No. There's so much more to soil than that. For a soil scientist in general and a soil microbiologist in particular the soil is a living thing, a mixture of living and dead organisms in an organic/mineral matrix. Not every organism is identical, or as abundant, or does the same things, or is active at the same time. Some you can see and some you can't, although we have various tools we can use to prove even the microscopic ones exist. Soil is the most immensely complicated and diverse ecosystem on the planet. And as the quotations above suggest, its care and feeding are vital to agriculture and vital to life.

Why Soil Biology Matters

The skin is the largest organ in the human body. Without it we would die. The soil is the skin of the Earth. Without it the Earth - ourselves included - would also die. The soil provides our food, recirculates our air, and purifies our water. It does so constantly, quietly, and through agents mostly unseen. It is the stomach, lungs, and kidneys of Earth and we quickly realize it when something goes wrong. The soil teems with life. In every square yard of soil there may be thousands of different species (Atlas, of Diversity, 2016). If you think about bacteria alone, a single gram of soil (about as much as a raisin) can have as many as 10,000 unique genetic signatures. Consider all the cattle and ranchers above-ground and how much they weigh. A good

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s Feeding the soil population means providing it with enough carbon (C). That can take many forms: plant litter, compost and manures, and plant root exudates. The important thing is to maintain crop cover at all times. While crops harvest C from the atmosphere and feed it to the soil organisms in the rhizosphere, those organisms churn up soil organic matter and transform minerals to make nutrients plant available. Unhealthy looking plants are unlikely to Figure 7. Arbuscles inside plant root cells sustain an active soil biology. Likewise, soil are the struct ures by which mycorrhizal organisms thrive on diversity, so a diverse fungi exchange nutrients and C with plant selection of plants growing in the soil roots (fmage courtesy of J. Hendrix). environment makes for a greater diversity of soil organisms. The concept of 'Soil Health' holds that optimizing the biological, physical, and chemical environment of the soil will promote the most sustainable environment for biological activity. Physical management includes reducing compaction and foot traffic. Both reduce porosity and create smaller pores. In addition to making it more difficult for plant roots to grow in that environment, compaction reduces aeration and slows the rate of biological activity in the soil environment Soil organisms need air too in order to thrive. Chemical management includes optimizing fertilizer additions and particularly optimizing pH. Managing for soil health indirectly does the things that will manage for healthy soil life.

Conclusion

"If you build it, they will come." That's not necessarily true of the organisms in soil. They are already most likely there already (in one form or another). Rather, "If you manage it, they will thrive." The soil is alive and living things respond to good management. A living soil requires management to function best for the ecosystem services it provides in terms of producing food, fuel, fiber, and forage. The better the management, the better the function.

References

Orgiazzi, A., et al. (Eds.), 2016, Global soil biodiversity atlas. European Commission, Publications Office of the European Unjon, Luxembourg.

29 Credits

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Acknowledgements

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program,

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supported

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(Eds

grants

of

.

the

), Multistate

2016

from

European

,

the

Global

Project:

following

Union,

Soil

Soil

Biodiversity

Luxembourg. sources:

Organic