Unless a peanut stand is really poor — one plant per row foot or less in single rows, and 2.25 plants per foot in twin rows — replanting is rarely profitable, says Jason Sarver, Mississippi Extension peanut agronomist.
Supplemental seeding in a sparse stand can sometimes show an advantage over a poor stand, he said at the annual conference of the Mississippi Peanut Growers Association, but in most cases the most practical thing with a less-than-ideal stand is to give it careful management through the season.
“Stand establishment is critical for a successful peanut program,” he says. “Based on my research in Georgia over the last three years, we need 3 plants per foot on single rows, or 3.75 plants per foot on twin rows in order to maintain yield potential.
“In those trials, destroying an initial poor stand and completely replanting was never a viable option. If you decide to replant, supplemental seeding — moving the planter over and adding a reduced rate of seed — is usually the best way to go.
“Although adding seed to the initial stand costs less than completely replanting, the biggest potential negative is that multiple planting dates will result in plants with varying maturity within the same field. This can pose problems when deciding when to harvest, as plants from both the initial and later planting dates must be considered and balanced.”
In the complete replanting scenario, he says, “You have increased costs in destroying the stand and the cost of planting a full rate of seed a second time. And you end up planting late. Recent data from Georgia show that, on average, yield potential begins to drop after May 10.
“So, if you originally planted May 10 and have only 1-1/2 plants per foot, and you don’t make the call to replant until the end of May, the question you have to ask is, are you better off with the original 1-1/2 plants from the May 10 planting or with a potential full stand by replanting May 31?
“Based on what we saw in the Georgia studies, unless we had a stand below 1 plant per foot in single rows or 2.25 plants per foot in twin rows, there was no statistical advantage from either supplemental seeding or total replanting.
Importance of establishing a stand
“This really drives home the importance of establishing an adequate stand in the beginning, because while 3 plants per foot in single rows and 3.75 plants per foot in twin rows is optimal, in our research if we didn’t get that, we were actually better off keeping the original stands, unless they were very poor.
“Below 3 plants per foot, we started losing yield. On average, across two locations in each of two years, every 1/2 plant per foot reduction below 3 plants per foot resulted in a yield loss of 201 pounds per acre. At $500 per ton peanuts, those are pretty substantial losses attributed solely to plant stands.”
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Twin rows can support somewhat higher stands, Sarver says. Across two locations and two years, average yield was 6170 pounds at 3.75 plants per foot. When plants per foot of row were reduced to 3 and 2.25, yield was reduced by 400 pounds per acre and 456 pounds per acre, respectively.
But again, Sarver says, replanting “was rarely a good option in the Georgia trials — there’s just too much to overcome with a later planting date. And I think that will be the case here in Mississippi, too.”
While those yield reductions were observed, it’s important to note that good yield potential is still there at low plant stands, he says.
“In single rows, yields still averaged 4800 pounds at 1.5 plants per foot and in twin rows yields averaged 5700 pounds at 2.25 plants per foot. While low stands can make a field look bad early in the season, and options for growers with poor stands are limited, these results show that with proper management, respectable yields can still be achieved even when plant stands are disappointing.”
With many growers moving to earlier planting of peanuts, Sarver discussed studies on the impact of soil temperature on germination rate.
“From the late 1980s through the mid-1990s, 25 percent to 50 percent of our peanut acreage was planted in April. Then tomato spotted wilt virus came along, wiping out large percentages of the crop.
“Thrips are a vector for the disease, and to lessen the impact of this pest, the recommendation was made to move back the planting window for peanuts to reduce the risk of TSWV. “Today, GA-06G has become basically our industry standard variety in the Southeast, and it has such a good disease resistance package that the recommendation has started to shift back to ‘plant as early as soil and weather conditions will allow.’”
But, Sarver notes, this often means planting when air and soil temperatures are colder.
Warmer soil more favorable for germination
“Historically, the recommendation has been to start planting when you have a 65 degree soil temperature at 4-inch depth for a minimum of three days and a favorable forecast. But, recent evidence indicates that this recommendation might need to be reevaluated.”
Studies at the University of Georgia Tifton Campus were conducted by Dr. John Beasley, Dr. Tim Grey, and Beasley’s graduate student, Jason Arnold, under controlled conditions, to determine how soil temperature affects seed germination.
The tests covered a temperature range of 55 degrees to 75 degrees in 1 degree increments, and germination was recorded every 24 hours, starting at 48 hours after initiation.
For the Georgia Greener variety, Sarver says, “The 65 degree soil temperature results were pretty striking. All the way out to 7 days, they only reached approximately 65 percent germination. At 3 days after initiation, germination was only at about 10 percent.
“When moving to 70 degrees, at 7 days germination was 90 percent, and at 74 degrees, it was 95 percent. For Georgia 06G, results were similar. At a 65 degree temperature, germination was about 70 percent after 7 days, while at 70 to 74 degrees, germination was 90 percent to 95 percent, respectively.”
While there may be some additional germination after the 7-day period, Sarver says, “The longer seed are in the ground, the longer they are exposed to soil borne pathogens, which may cause stand loss. An extended germination window also causes uneven plant emergence, which can lead to varying maturity within the field and harvest issues late in the season.”
While the data are from only one year of an ongoing two-year study, Sarver suggests that the results are worthy of consideration by growers.
“These results illustrate how sensitive peanut seed are to soil temperature. Based on what we know about the need to establish an adequate stand, it will benefit growers to err on the side of caution and wait until soil temperatures are closer to 70 degrees in order to insure rapid, uniform germination and emergence.”