On July 15, Georgia Organics and Coastal Organic Growers hosted an organic peanut field day at Healthy Hollow Farms near Stilson in southeast Georgia. This was a unique opportunity for growers interested in organic farming not only to visit the only certified organic peanut farm in Georgia, but also to learn production practices on a large-scale organic operation. Speakers at the organic peanut field day included Connie and Jimmy Hayes, owners of Healthy Hollow Farm, Dr. Albert Culbreath from the UGA Department of Plant Pathology, and Dr. Carroll Johnson, a research agronomist in weed science with USDA-ARS.
Although Georgia produces nearly 50 percent of the U.S. peanut crop and boasts yields above the national average, the vast majority of certified organic peanuts are grown in the Southwest region of the country, where the hot, arid climate inhibits insect and weed pressures. However, the sandy soils of the Coastal Plain have proven to be fertile ground for growing peanuts organically, and most of Georgia’s certified organic production occurs in its southeastern section (See Figure 1). Shirley Daughtrey and Relinda Walker, two of the earliest producers of certified organic peanuts in Georgia, attended the field day and shared their knowledge growing in Effingham and Screven counties, respectively. Their experiences echoed statements by the researchers on hand: establishing good stand and timely mechanical cultivation are keys to successful peanut production on both organic and conventional farms.
Peanut Variety & Disease Management
One of the challenges organic peanut production faces is a variety suitable for organic production. Selecting varieties that have full or partial resistance to disease common among peanuts is the best way for organic peanut farmers to prevent disease. The main diseases that plague peanut farmers are tomato spotted wilt virus (TSWV), and early and late leaf spot.
“[Tomato spotted wilt] is a disease that came close to putting us out of peanut production in Georgia in the 90s,” Culbreath said. But more recent peanut varieties, including the popular Georgia-06G, have tomato spotted wilt resistance and “tremendous yield potential.”
Culbreath has also been working with an experimental breed that he says is “promising” for organic and small-scale production. The variety, CRSP-192T, was developed by Dr. Roy Pittman and Dr. Jim Todd and was planted this season at Healthy Hollow Farm. It has partial resistance to tomato spotted wilt virus and early and late leaf spot. The variety matures slightly earlier on average, which is beneficial for organic producers trying to outcompete weeds. Another plus to this experimental variety? Unofficial taste tests give the flavor of both the boiled and roasted peanuts a thumbs up.
Culbreath’s research has shown that not only is variety an important decision when developing a disease management plan, but other cultural practices are also key, as organic growers cannot use chemicals that are not on the National List of Allowed and Prohibited Substances. Crop rotation is one of these cultural practices, along with copper fungicides, which are approved for organic use.
“What [Culbreath] is working on, the disease resistance and the disease tolerance, that’s got us in the ballgame right now,” said Johnson.
Johnson’s research is also extremely valuable, as weeds are a major problem in both conventional and organic systems, particularly palmer amaranth.
“[Palmer amaranth] is the most troublesome weed in almost every crop grown in the South,” said Johnson. “In ten years it’s gone from basically obscure to (…) dominating how we grow crops or what crops we grow.”
With large tap roots and half a million seeds, this plant is not only physically hard to remove from the field, but also can make deposits into the soil weed seed bank. Because palmer amaranth produces an abundance of seeds and cross-pollinates, it developed mutations with resistance to glyphosate and rapidly reproduced those mutations across the country. “This is a man-made problem, it’s pure and simple,” said Johnson, “And now that we’ve got the horse out of the barn, we’ve got to find a way to corral it. There’s a lot of research talent trying to solve this problem, but unfortunately it’s after the fact.”
Knowing how to control this prolific weed without chemicals is not only useful knowledge for organic growers, but conventional growers as well. Reliance on glyphosate to control palmer amaranth in conventional systems has enabled the plant to develop tolerance to the common herbicide.
“Most [palmer amaranth weeds] are resistant to glyphosate,” said Johnson. “The attribute for herbicide resistance is in the pollen and that’s why it is spread so rapidly throughout the whole eastern U.S. and the Mid-South and other similar species up in the Great Plains.”
Research has shown that mechanical cultivation is an effective weed control method for palmer amaranth. Using a tine weeder three to four days after planting and repeatedly on a weekly or bi-weekly basis after the initial pass-through removes weed seedlings from the field before they have a chance to outcompete the crop. The key is to begin early and remove weeds before they have a chance to establish. Johnson’s rule of thumb is if you see the weeds in the field, it’s too late.
However, in Johnson’s opinion, the most troublesome weed for peanut production isn’t palmer amaranth at all, but annual grasses, because of the large root masses they form.
“The peanut pods themselves are going to be forming in the root mass and you try to dig peanut that has a lot of crabgrass in it, or any annual grass, as you try to dig them and lift them out of the ground the pods are going to get wrapped up in these roots and they’re going to shed,” explained Johnson. “You’ll have a lot of harvest losses. So you’ve already had yield reduction from competition then what you’ve produced you’re losing a good bit because of harvest losses due to these weeds. That’s why this is the one that I think really needs to be the focus for everybody. Keep annual grasses from becoming troublesome in any crop, particularly peanut.”
The tine weeder is also effective on controlling annual grasses. Innovations to help control perennial weeds, such as bermudagrass, are also promising for the future of weed control, especially in organic systems. Currently, the senior class of Auburn University’s Mechanical Engineering school is working on an implement for peanut diggers that will collect weeds and hydraulically move them to a cart where they can be taken from the field.
“The students have designed this and their building it right now…, and it is incredibly impressive to see these young people working on something like that,” said Johnson. “I think there’s some opportunity there for a lot of innovation and a lot of business innovation too.”
Georgia Peanut Tour
For those who would like to see organic peanut production up close, Healthy Hollow Farm will be featured on the Georgia Peanut Tour, which will take place in the Savannah area on September 16-18.