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Maryland farmer wonders whether Roundup residue played role in low yielding legumes, greens

by Robert Schubert
CropChoice editor

(Monday, Oct. 28, 2002 -- CropChoice news) -- Jay Martin's first clue came early last summer when he noticed the morning glories. The first runners looked healthy, but others were shriveled and dying.

"I figure when you see weeds suffering, something is really wrong," says Martin, who grows leafy greens, legumes, potatoes and fruit without the use of synthetic pesticides or fertilizers on his Provident Farm near Salisbury, on the eastern shore of Maryland.

Unfortunately for Martin, the problem grew beyond the weeds. It was the same story with his leafy greens, peas and string beans-- poor germination, low yields and ill looking plants.

All of this played out on a small portion of 10 acres that he had acquired prior to the start of the 2002 growing season. The acreage had been part of a large soybean operation. In the last 8 years before retirement, the farmer had relied exclusively on Roundup to kill weeds in his fields. That probably meant he applied the herbicide before the soybeans sprouted and after harvest. In later years, Martin says the farmer grew Roundup Ready soybeans, which Monsanto genetically engineered to resist glyphosate, the active ingredient in Roundup. That would have allowed the farmer to spray the weed killer during the growing season without harming the soybean plants.

Martin wonders whether glyphosate residue in the soil might have caused the agronomic problems on the ground that he hopes will one day be certified as organic.

Poor growth characterized all of the kale, collards, and cabbage he planted late in the winter for harvest in the spring. Cabbage weighed half a pound, far below the normal weight of 4 to 5 pounds.

He also sowed string beans on his newly acquired ground. The lower foliage on all the plants turned yellow around the time of flowering and they were stunted -- only 8 inches tall. Three pickings yielded a total of 36 pounds instead of the usual average of 160 pounds.

Stumped, Martin tested the soil. After taking an initial sample, he added compost and lime, and then sampled the ground again. The first soil specimen revealed low nitrogen and low Ph, with an organic matter content of 2 percent. The second, post-amendment sample showed organic matter of 4.5 percent with a ph of 6.4; he also fed kelp to the foliage. A horticultural specialist from the University of Maryland extension service looked at both soil tests but had no explanation for the condition of the plants.

Alas, this did not markedly improve the situation. "The fertility was there," he says. "It think it just was not available to the crops because of the non-existence of soil microorganisms that convert it to a useable form."

Although a drought was happening at the time, Martin irrigates. And in later plantings, with adequate soil moisture, the problems persisted.

Finally, he resorted to sidedressing plants with bloodmeal. But it wasn't until applying twice the recommended rate that he finally saw results in his last planting of string beans. That 200-foot row yielded 120 pounds of beans, still below the average of 160 pounds. Later fall plantings of leafy greens are doing well where he doubled the dosage of the fertilizer.

"I attribute this to the bloodmeal and the duration of time since Roundup was last applied, probably about 15 months now," he says. "Bloodmeal is one of the fastest acting, most readily accessible forms of nitrogen that organic growers can use. I see it as a rescue operation. The goal in organic farming, of course, is to build the soil and not to have to perform rescue operations. This is the organic equivalent of the nitrogen that chemical farmers use."

Martin compared tomatoes -- same variety and planting date -- on ground that he's worked for 16 years with those on his agronomically challenged area. The plants close to home bested the others by three times, both in terms of the number of weeks they bore fruit and the amount of saleable tomatoes.

The unconventional scoop on Roundup, a supposedly safe herbicide.

Caroline Cox, staff scientist with the Northwest Coalition for Alternatives to Pesticides, has studied and written about Roundup, including the persistence of its active ingredient, glyphosate.

"Long persistence has been measured in the following studies: 55 days on an Oregon Coast Range forestry site; 249 days on Finnish agricultural soils; between 259 and 296 days on eight Finnish forestry sites; 335 days on an Ontario (Canada) forestry site...and from 1 to 3 years on eleven Swedish forestry sites. EPA's Ecological Effect's Branch wrote, 'In summary, this herbicide is extremely persistent under typical application conditions,'" according to her paper in the Fall 1998 issue of the Journal of Pesticide Reform (Vol 18, no. 3), available at http://www.pesticide.org.

Roundup can harm humans and sour agronomic performance. Farmers exposed to it have experienced increased risk of miscarriages, premature births, and cancer. It can kill the beneficial insects that feed on agricultural pests, Cox says. In lab experiments, glyphosate reduced the activity of mycorrhizal fungi in the soil around plant roots, inhibited plants' ability to fix nitrogen, and decreased their defenses against pests.

The "use of genetically-engineered glyphosate-tolerant crop plants means that nitrogen-fixing bacteria in field situations 'could be affected by repeated applications of glyphosate,'" Cox wrote.

More recent studies of Roundup Ready soybeans have uncovered some glitches.

Not only does glyphosate inhibit normal root function, and thus yields, a University of Missouri team found increased levels of Fusarium species after Roundup applications. One species, Fusarium solani, is a catalyst in the Sudden Death Syndrome that is a growing problem in some Midwestern areas.

"The Missouri researchers' work shows that "Fusarium levels tend to build up in fields treated year to year with Roundup, an increasingly common occurrence as both RR soybeans and RR corn gain popularity. This suggests that something related to the root exudates or crop residues in RR fields may be having a sustained effect on soil microbial community dynamics, perhaps through the mix of compounds in leaf and root tissues that remain after the crop is harvested and break down in the soil over many months post-harvest," wrote Charles Benbrook, Ph.d. in his May 2001 report, "Troubled Times Amid Commercial Success for Roundup Ready Soybeans: Glyphosate Efficacy is Slipping and Unstable Transgene Expression Erodes Plant Defenses and Yields." (http://www.biotech-info.net/troubledtimes.html)

Does Caroline Cox think Roundup caused the problems on Martin's farm? "It's not an unreasonable hypothesis, although the necessary kind of investigation and data collection hasn't been done."

As for University of Maryland officials, they didn't believe it and were unwilling to study the problem further. Monsanto says Roundup is safe, one of the most benign herbicides available. The farmer who grew soybeans, both conventional and genetically engineered Roundup-resistant types, on the acreage couldn't be reached to comment on whether he saw progressively declining yields after applying Roundup.

Martin has a suggestion for any grower attempting to convert land sprayed with Roundup: "If you're unable to put in a cover crop in the fall or not willing to spend a lot of money on expensive bloodmeal, do not attempt a spring crop. Instead, wait until the following fall after a heavy application of compost and a summer cover crop."