Monday, December 3, 2012

A Secret Underground World

Does this banana plant grow well here because of the soil, 
or does it help create soil that enables it to grow here?

Acclaimed gardening author Jeff Lowenfels comes to Duke Gardens for a guest lecture and a workshop Dec. 15. rescheduled to April 27 & 28, 2013. Learn more below.

By Jan Little

Our world is amazing. New information and discoveries continue to surprise and delight us, including research about soil. And now you can add soil to the list of party conversation starters with amazing new information about the world under our feet.

Several hundred years ago, Leonardo da Vinci noted that “we know more about the movement of celestial bodies than about the soil.” That is now changing, and the story that is emerging is incredibly fascinating.

This story involves a web of micro-animals, bacteria, fungi, nematodes, plants and roots and, moving up the food chain, insects, amphibians, small mammals, birds, and finally humans. It is commonly referred to as the soil-food web.

We are just now beginning to understand that plants don’t just grow where conditions are hospitable to their needs—plants actually shape and change the soil to suit their requirements more closely. So the plants in woodland settings will help produce a soil that is significantly different than that of the plants in grasslands.

When this system of plants, soil and animals is in balance, it is entirely sustainable and there is no depletion of the soil. The system is far older than humans—it just took us this long to catch on and begin to understand it. And this understanding helps us create lower maintenance, sustainable gardens.

Each layer of this soil food web has a job to complete. For example, the bacteria, fungi and some insects act as the world’s garbage disposal systems. Not only does this tidy up our world, it also recycles nutrients and makes those tasty tidbits available to plants. Quite simply, we would not have any food if the decomposers did not complete their jobs.

All of this information will lead us to some fairly significant changes in how we work with our garden soil. Managing your soil-food web will encourage you to stop using synthetic fertilizers. These fertilizers give a quick shot of nutrients to the plants, but over time they kill the soil biology and stop the ongoing processes of the soil-food web. Instead, use compost, organic fertilizers and healthier gardening practices.

This also encourages us to discontinue the annual rototilling of garden soil. Rototilling disrupts and destroys the soil biology, and over time it depletes soil of its structure and fertility. Generally it is suggested that breaking up the soil as you establish a garden is fine, but after that you should use sustainable maintenance practices to build the soil and the soil-food web.

You can learn more about the soil-food web with author Jeff Lowenfels when he visits Duke Gardens this month. Jeff is giving both a small group workshop on creating and using compost teas (Dec. 15 rescheduled to April 27, 2013, 9 a.m.-noon) and a lecture on the soil-food web (Dec. 15 April 28, 2013, 2-4 p.m.). This is based upon his research for the book Teaming with Microbes: The Organic Gardener's Guide to the Soil Food Web, originally published by Timber Press in 2006 to great acclaim.

Jeff’s book has been enthusiastically reviewed, and it was touted as the most important gardening book published in the past 25 years. He won the prestigious Garden Writers of America Gold Award for gardening books when Teaming with Microbes was originally published. We now have the opportunity to read a new edition published in 2011.

If you’d like to register for Jeff’s workshop or lecture, or learn more about these or other events at Duke Gardens, please call our registrar at 668-1707 or send an email. Duke University staff and students may attend for the Gardens member discount price.

Sarah P. Duke Gardens creates and nurtures an environment in the heart of Duke University for learning, inspiration and enjoyment through excellence in horticulture. The Gardens is at 420 Anderson St.

Jan Little is director of education and public programs at Duke Gardens. This column first appeared in the Durham Herald-Sun.

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