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[Gene GeRue <genegerue AT ruralize.com>]

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