Weed management in organic crop production is not for the faint-hearted or for wimps. Even in a good year, organic production is risky, and 2011 has highlighted those risks, says Carroll Johnson, USDA-ARS in Tifton, Ga.
Weed control is the major limiting factor in organic farm production, says Johnson, especially in peanuts. “We’ve been working on this since 2004, but this is the first time we’ve tried it at the Expo site,” he said during this summer’s Sunbelt Ag Expo Field Day held in Moultrie, Ga.
“Our intent is to try and capture some of the increasing demand for organic food staples, especially organic peanut butter. Most of these type products now are imported from other countries. There’s no reason why we can’t grow organic peanuts and sell organic peanut butter in Georgia — that’s our goal,” says Johnson.
The Expo demonstration was designed to show the feasibility of organic crop production and techniques of weed management with an emphasis on peanuts. Millet also is part of the demonstration, being grown in rotation with peanuts.
“As everyone is painfully aware, the 2011 growing season has been an absolute nightmare up to this point,” said Johnson during the first week of July. “Unusually hot temperatures created a terrible set of circumstances prior to establishing a stand. We have routinely had soil temperatures 2 inches deep that are as high as 117 degrees F. If you try to plant untreated seed — which is what you do in organic farm production — in soil that hot, you can water it all you want and it doesn’t do much good.”
Johnson was making his third attempt to plant at the Expo site since mid-May.
“We finally were able to get it in, but we ran out of untreated peanut seed. In our first attempt at planting organic peanuts here, we had less than a 20-percent stand,” he says.
One of the concepts of weed control being used in the trial is a tine weeder, says Johnson. “It’s an imported implement from Austria, and the key to weed control in any crop is to get a good stand, optimal row spacing, optimal seed placement and frequent and intense cultivation.
“Peanuts will tolerate abuse from this implement. The ideal stage for beginning cultivation for organic peanut production is at cracking. If you see any weeds at all, it is too late.”
Weed control in organic crop production is based on an integrated system of cultural, mechanical and physical weed control efforts, he says. Reliance on a single form of weed control, says Johnson, will result in failure.
Best weed control practices
For cultural weed control in organic production, he advices the following:
• Use conventional-tillage production systems.
• Plant disease-resistant varieties and high-quality seed.
• Order non-treated seed in early winter from regional seed suppliers.
• Plant peanuts in May when soil temperature and moisture are ideal. Avoid planting when soils are too cool or too hot.
• Plant peanuts in 36-inch rows, with six to eight seed per foot. Seed should be placed two to 2.5 inches deep in sandy soils.
• Optimum and uniform stands are a necessity. Replant or supplement plant to achieve uniform, non-skippy stands.
For mechanical weed control, a tine weeder is the implement of choice, says Johnson. Growers should cultivate with the tine weeder three to four days after planting, prior to peanut emergence.
Cultivation should be on at least a weekly basis for six to eight weeks, periodically substituting with sweep cultivation if broadleaf weeds are present.
Organic producers should consider hand-weeding as supplemental or secondary to cultural controls and cultivation. Hand-weeding should be done primarily to control escapes, he says.
If cultural controls and cultivation have been effective, hand-weeding will be minimized, says Johnson.
University of Georgia Extension specialists and researchers continue to showcase how various peanut cultivars respond to single and twin-row patterns at the Expo.
“Row pattern research on peanuts has been going on for a long time,” says John Beasley, UGA Extension peanut specialist. “We looked at the older cultivars like Florunner back in the 1970s, and since the mid-1980s, we’ve tested every cultivar for a response to twin and single-row patterns.”
The beauty of it, says Beasley, is that peanut breeding programs in the Southeast are turning out outstanding cultivars. “Whenever a cultivar is released, we test it for row-pattern, plant population, planting date, and all the other factors that we need to test,” he says.
In the Expo trial, researchers continue to look at twin versus single-row peanuts.
“Last year, we averaged just below 5,900 pounds per acre at this site. We had eight cultivars, planted in single versus twin rows. Averaged over the cultivars, there was 10 pounds difference in twin versus single rows.
“You might say twin rows just don’t work anymore, but last year we had outstanding growing conditions and the single-row pattern took advantage of that. We see that from time to time, and we still believe strongly in the impact of the twin-row pattern and the advantages it offers in certain situations.”
This year, two cultivars were dropped and two were added to the test. “For the first time since 1999, we do not have Georgia Green in our trial — not only here but in any of our trials. It’s a cultivar of the past even though it was the standard for several years. We also dropped AT-4. We added GA-10T and FloRun 107,” says Beasley.