Healthy soil and sustainable growing

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Would you like some DDT with that organic cucumber?
Stephanie Paige Ogburn | Dec 10, 2010 02:10 PM
http://www.hcn.org/blogs/goat/would-you-like-some-ddt-with-that-organic-cucumber

Consumers might assume that buying organic means the produce they purchase 
lacks chemical residues and the farmers and farm workers growing organic 
crops aren't exposed to toxic chemicals. This may not always be the case. 
Organic farmers across the nation must contend with the possibility that the 
land they farm has some of the very chemicals their farming methods are 
designed to avoid.

As Rebecca Clarren's recent cover story, Farming's Toxic Legacy, revealed, 
many former agricultural lands remain polluted with remnants of now-banned 
pesticides. Some, like the chlorinated hydrocarbons dieldrin, aldrin, and 
DDT, have dangerous breakdown products that remain in the soil for a hundred 
years or more. Others, such as the insect-killer lead arsenate, break down 
into the elements lead and arsenic, which never go away unless soil is 
removed.

In Oregon, the only state where extensive testing on organic farmland was 
ever conducted the certification body Organic Tilth found remnants of those 
chlorine-based pesticides on much of the farmland that organic producers now 
use. These tests took place in the early years of the organic movement during 
the 1970s and 1980s when earnest farmers were trying to figure out what sort 
of land they were growing on; ever since the United States Department of 
Agriculture codified organic certification in 2002, soil tests for chemical 
residues have been voluntary.

"If they [chlorinated hydrocarbon pesticides] were ever put on, for any 
reason, they're probably still there," says Harry MacCormack, a farmer who 
headed up much of the group's soil testing on farms around the Willamette 
Valley. In an ironic twist, high quality soils, known as "Class 1," are more 
likely to have pesticide remnants, because they were probably used early on 
for ag production.

Vegetables in the squash family, like cucumbers, zucchini, winter squash 
(frequently used to make organic baby food) and melons all bioaccumulate 
chlorinated hydrocarbons in their tissue; if it's in the soil, it's likely 
it's in the cucumbers grown in that soil.  Root crops like potatoes and 
carrots also tend to soak up these pesticide remnants, says MacCormack.

cucumber

Vegetables in the cucumber (cucurbit) family, like squash and melons, all 
tend to uptake remnants of certain pesticides. Photo courtesy Flickr user 
Larry Hoffman.

The laws governing the transition to certified organic under the USDA require 
producers to wait three years before growing certified crops on land that was 
once conventionally farmed. While it is true that organophosphates, another 
class of popular pesticide that includes malathion and parathion, usually 
break down in three to five years, other chemicals are far more persistent. 
The only way to really tell if chemicals have left the soil, and if the soil 
has built up sufficient quantities of nutrients, microbes, and organic 
matter, is to conduct soil tests.

When growers do find their soil has contaminants, there's no real way to 
clean it. Growers can remove contaminated soil and bring in new soil, a 
pricey undertaking. In Oregon, growers did an experiment trying to use squash 
crops to capture the DDT and other chlorinated hydrocarbons left in the soil. 
They purposely grew squash in contaminated soil, harvested and disposed of 
the vegetables that had bioaccumulated toxins, and then tested the soil to 
see if there was less contamination. This strategy ultimately did not work, 
says MacCormack.

If land does play host to long-lasting chemicals, consumers may not even 
know. Organic crops are rarely tested for residues [PDF, p.7], a failing the 
program has been criticized for, although USDA deputy secretary Kathleen 
Merrigan says program officials are trying to implement more frequent testing.

Organic baby food companies like Gerber have responded to consumer concerns 
by requiring their organic growers go beyond USDA requirements and conduct 
soil tests for toxic pesticide leftovers, so that they are not selling 
organic baby food laced with DDT.

Like many political processes, the creation of organic standards was a messy 
mix of science and compromise. Farmers today still complain that three years 
is too long a time to be in transition, as they suffer yield losses from not 
using synthetic chemicals without the price premiums from being certified 
organic. But without soil testing these farmers, the crops they grow, and the 
consumers they serve all may be exposed to the remainders of agriculture's 
toxic legacy.