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  • From: Gene GeRue <genegerue AT ruralize.com>
  • To: "homestead AT lists.ibiblio.org" <homestead AT lists.ibiblio.org>
  • Subject: [Homestead] Garden soil: it's much more than dirt
  • Date: Thu, 03 Mar 2005 08:02:53 -0700

The Push Is on for Good Clean Dirt
By ANNE RAVER

Published: March 3, 2005

I'd been an organic gardener for years before I really looked at pictures of soil under a high-powered microscope.

Mites were feeding on springtails. Fungi were swirling like strands of spaghetti around plant roots. Nematodes shaped like torpedoes were grazing on fungi. Everything was eating everything else.

Fascinated, I began talking to soil scientists and compost experts, learning that plants are not just taking up nutrients. They are exuding carbohydrates through their roots, feeding the bacteria and fungi that in turn break down nitrogen, protein, phosphorus and many other elements into forms the plant can absorb. For the first time, I began to grasp what I was dealing with in the soil of my garden: an underground city more complex than the infrastructure that powers Manhattan.

For the last 30 years, even as organic gardening grew from a fringe movement to a mainstream pastime, the science of soil has remained the province of microbiologists and plant pathologists, along with a few gardening geeks. But now there is an increasing awareness, even among casual gardeners, that soil has a huge effect on the success, or failure, of their gardens, and those gardeners are spending more money every year on soil-enriching products. Between 1999 and 2003, according to the National Gardening Association, the number of American households buying organic fertilizer nearly tripled, to 11.7 million.

And as everyday gardeners face a growing profusion of such products - from Peruvian seabird guano to compost tea brewing machines, from micorrhizal fungi to beneficial nematodes - they are trying to figure out which ones are valuable, which are little better than snake oil, and whether their gardens need any of them. For those who have found the right mix, the rewards can be considerable. "I had some pretty sad geraniums, but now the whole greenhouse is full of color," said Carol Magadini, a garden designer in Mendham, N.J., who has started using a compost tea on the plants. And after she started using a natural fertilizer on her moonflowers, which were "iffy," she said, "they had 50 blooms a night."

For gardeners who want to start taking soil seriously, the best way to begin is by taking samples and having them tested.

State universities usually offer testing services or will direct you to a reputable private laboratory. Ask for a textural analysis, which will indicate the percentage of clay, silt and sand in your soil, and how well it drains. And ask for a complete nutrient analysis as well, which will give you ammonium levels, elements and micronutrients. Such tests can range in cost from $15 to $75.

[I use a simple way to see the textural mix of my soil. I fill a quart jar about one-third full with dirt, add water nearly to the top, screw on a tight lid, shake vigorously for a minute or so until all soil is dissolved, and place the jar on the window sill in front of my kitchen sink. The next day the mix is obvious. The clay is on the bottom, the sand is next, then the loam, and the light humus is at the top. Serious gardeners also may want to buy their own soil test kits. --Gene]

Eric T. Fleisher, the director of horticulture at the Battery Park City Parks Conservancy, also recommends a simple percolation test. Dig a hole about a foot deep and half as wide, and scarify the sides with a garden fork or hand cultivator. Put two inches of sand or gravel in the bottom, fill it with water and note how quickly it drains. It should drain at least an inch an hour.

Most gardening problems have to do with poor drainage, said Mr. Fleisher, who manages 36 acres of organic gardens.

"Simply adding compost to heavy clay won't help, if you're not improving drainage," he said. So, depending on the density of your soil, you may have to dig down, with a pick ax and spade, 18 to 24 inches, just to break up that compacted clay. Then use a garden fork to mix in coarse washed sand, compost, aged leaves and aged manure.

Once you have workable soil, use that spade as little as possible. And put the tiller away. Every time you churn your soil into fine-grained cocoa, you are slicing through earthworms and killing beneficial organisms, toppling the delicate city that these organisms are building underground.

Professional analysis can also reveal problems with nutrients in soil, nutrients that, even if they are present, may be unavailable to plants for any number of reasons, from a lack of oxygen to an excess of nitrogen. Excess calcium, for instance, can inhibit the uptake of magnesium, boron and potassium, elements all crucial to plant growth.

"People often see browning on leaves and think it's a nutrient deficiency, when actually it's an excess of calcium or magnesium," said Dr. Olaf Ribeiro, a plant pathologist who runs the Ribeiro Plant Lab on Bainbridge Island in Washington.

Dr. Ribeiro has rallied failing 200-year-old Douglas fir trees in Olympia, Wash., he said, by applying compost full of micorrhizae, or beneficial fungi, which colonize tree roots, transporting nutrients and protecting the tree from disease. He has solved problems in citrus groves and vineyards by applying compost tailored to the needs of the soil and the particular plants being grown. And he sprays his own roses with sea kelp, which inhibits powdery mildew, he says, and makes the plants vigorous, the leaves a dark green.

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But gardeners who are unaware of the chemistry of their soil can often make problems worse, Dr. Ribeiro said, for example by pouring on fast-acting synthetic fertilizers. The extra nitrogen in such treatments may green up plants, but, he said, it also "helps pathogens to increase rapidly."

And poorly made composts or mulch full of pathogens can also cause serious damage, if not more, said Dr. William F. Brinton, the president of Woods End Research Laboratory in Mount Vernon, Me. "I would not buy any product sight unseen before knowing where it came from and what's in it," he said. "There is a lot of E.coli in compost that is improperly made."

Dr. Brinton, who has a doctorate in environmental science, is certainly not opposed to compost. He founded Woods End in 1975 to help companies make compost out of yard waste, crab shells, chicken manure and a myriad of other waste products.

"I thought compost would save the planet," Dr. Brinton said. "But compost is turning into a sleazy big business. There is a powerful waste lobby making money processing waste into compost," he said, without regard to what pathogens might be carried in the material.

Dr. Ribeiro also pointed to problems with mulch, or composted yard waste.

"Up here we get a lot of wood chips, which worries me, because they could be from diseased trees," Dr. Ribeiro said. Phytopthera, which can attack 1,000 species of plants, from potatoes to oak trees, is often spread through contaminated mulch.

So if you are buying mulch, get a printout from the company or municipal group providing it, listing everything in the material. "That means microelements to major elements," Dr. Ribeiro said. "You can have too much nitrogen in compost, or high levels of micro-elements like lead and cadmium."

And what about all the claims of miracle cures with compost tea? The ancients, from the Romans to my grandmother, just steeped manure in a bucket of water. But over the last few years fancy brewing machines that aerate compost mixed with water have become the new Cuisinarts of the garden. The resulting teas are supposed to cure everything from powdery mildew to potato blight. There are testimonials from potato and citrus growers, golf course superintendents and public garden directors. But so far these testimonials haven't been backed up by scientific studies. Scientists warn that the teas can be infected with pathogens if they are improperly made.

Dr. Brinton was one of 13 scientists on the Compost Tea Task Force organized by the Department of Agriculture's National Organic Standards Board, which completed a study of the efficacy of compost teas in 2004.

"We came to the conclusion that with the uncertainty of compost quality out there, there's considerable risk," he said.

The best way to know what you're getting, of course, is to make your own compost, and local botanical gardens can teach you how to do it. Cities and counties often give away composted yard waste. And don't bag up those leaves for the trash collector. Let them decay right under your tree, to feed the soil. Or put them on your compost pile.

[Shred leaves with your mower before putting them on the compost pile. Unshredded leaves make a thick, slimy impervious layer and take forever to break down. --Gene]

I've been making my own compost for 30 years. I've raised red worms and spread their castings on my house plants. I've mulched my garden with seaweed gathered along the bay. But I've only just begun to discover the secrets of the soil.

http://www.nytimes.com/2005/03/03/garden/03cutt.html?pagewanted=1






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