Harvesting peanuts too late can hurt your bottom line. However, deciding optimum harvest date can be a little tricky and should include considering canopy health leading up to harvest as well as crop maturity and harvest capacity.
When to dig
"I use a combination of factors to determine optimal harvest maturity," said Brendan Zurweller, Mississippi State University Extension peanut specialist and research professor. "The first involves the tried and true method of pod blasting and using the peanut profile board to get a predicted number of days to dig."
With the maturity profile board, Zurweller also determines the percent of black, brown, and orange pods of each maturity sample.
"My goal is to try to reach at least 70% black, brown, and orange pods," he said. "Last year, we started tracking what the percent change in black, brown, and orange pods are per day with Georgia-06G to better predict when this target is reached."
They observed an average of about 0.78% change per day during September into early October.
"I also track growing degree days," Zurweller said. "If using a base of 56 degrees, our initial studies show optimal harvest timing is about 3,330 cumulative thermal units for Georgia-06G."
Factoring planting dates
Another method of determining when to dig is by examining planting dates.
"An additional factor I like to account for when deciding when to dig is to approximate the minimum number of days it’s going to take to pick all the peanut acreage," Zurweller said. "This changes based on a grower's harvest capacity and how spread out the planting dates are. I think this helps to be practical about how early one needs to begin digging and how many acres to dig at one time.
"Some people base when to dig on days after planting, which can have a little bit more variability. The general rule of thumb in the Southeast for optimum maturity for a variety like Georgia-06G is around 138 days. My goal is always to be wrapping up harvest by about mid-October.
"Sometimes, though, it gets wet, and you can't get in the fields. There's not a whole lot you can do if that happens, so timeliness is critical."
These methods predict the optimum maturity of the crop to maximize both yield and grade. When considering the optimum maturity of a whole crop, it pays to be a little early.
"Weather is always a factor," Zurweller said. "It's better to start a little earlier and give up a little grade than to start digging too late. You have about two to three weeks after the optimal time to harvest before pods become over mature, and when you dig, you will start losing pods. An average of one pod on the ground per row foot can be as much as 40 pounds per acre loss. It can start to add up fast if the crop is overmature and can be exacerbated by a too fast ground speed."
Preserving canopy health
Currently, disease management is at the forefront of farmers' concerns.
"One tip is to reflect on how well your disease management programs have performed in the past at maintaining late-season canopy health," Zurweller said. "If certain fields have had issues with low late-season canopy health from disease, I would consider adjusting by increasing the number of sprays or utilizing a different combination of fungicides.
"It's important to maintain good canopy health going into the fall to decrease the risks of early defoliation. As we get closer to fall, it will be time to determine when the optimal maturity is and adjusting the estimate based on harvest capacity and, of course, the weather."