What are the current recommendations on lime, gypsum or gypsum replacement products?
Peanuts, a legume, provide their own nitrogen through a symbiotic relationship with bacteria, and the deep tap root is good at scavenging residual soil phosphorus and potassium. That often leaves calcium as the next limiting element. A lack of adequate calcium can reduce yields because of a lack of kernels. It can also increase pod rots and in seed peanuts, a lack of calcium can affect germination rates.
The University of Georgia Extension recommends taking a pegging zone soil sample at 4 inches deep soon after peanut emergence. If the results indicate either 1) less than 500 pounds of calcium per acre or 2) a calcium-to-potassium ratio of less than 3:1, then it is recommended to apply 1,000 pounds per acre of gypsum at early bloom — approximately 30 to 45 days after planting. Peanuts to be saved for seed should automatically receive 1,000 pounds per acre of gypsum at early bloom even if these levels are met.
A fall soil sample, while it is likely better than nothing, is likely taken deeper than the pegging zone. Also, calcium can leach out of the pegging zone between a fall sample and early bloom with enough rainfall. Finally, if you take a fall soil sample and then deep turn before planting peanuts, you can very possibly turn up soil into the pegging zone that is low in calcium.
Rates And Replacements
University of Georgia Extension peanut specialist Scott Monfort says early indications this spring about possible gypsum shortages have producers talking about rates and possible alternative gypsum products. The following are some of his recommendations on both.
“For fields below 750 to 800 pounds per acre of calcium, based on calcium pegging test, gypsum is worth the investment even at $50 per acre for 1,000 pounds,” he says. “You could reduce the amount applied to 750 to 800 pounds per acre to save some money.”
For fields above 800 pounds per acre, cased on calcium pegging tests, Monfort says there are alternative products to gypsum that will help reduce the risk of calcium deficiencies for peanut but will not help in building calcium in the soil for the next crop.
Those products include Top Flow at 10 to 15 gallons per acre applied at planting or early bloom and watered in immediately after. “With this product, you will likely increase pH by half a point,” he says.
Another product is calcium chloride at 10 gallons per acre injected through the pivot at 50 to 60 days after planting. Another option is calcium thiosulfate at 20 gallons per acre through the pivot also at 50 to 60 days after planting.
Calcium Reminders
As a reminder, calcium products applied through the pivot are considered soil applied because the amount of water used moves the calcium to the soil line. Foliar products do not provide the calcium needed because calcium does not translocate through the plant from the leaves to the pods. Calcium has to be absorbed with water directly through the walls of the developing pods in the pegging zone, the top 4 inches or so of soil, not through the roots or any other part of the peanut plant.
“Gypsum is still the best option on seed peanuts. All other products will not supply enough calcium,” Monfort says. “Lime is another way to get calcium to the crop if a pH adjustment is needed and the lime is applied prior to planting.”
Virginia Variety Recommendations
David Jordan, North Carolina State University Extension peanut specialist says producers of Viriginia-type peanuts should apply gypsum prior to pegging but not too early in June.
“Use recommended rates,” he says. “If you apply higher rates of gypsum in fields with lower pH, you could see a yield loss.
“My recommendation is late June at the earliest for gypsum in peanuts. Peanut vines need some size to keep the gypsum on the soil surface if you get heavy rains. Late kernels need adequate gypsum well into the season. I think early to mid-bloom is a good timing,” he says.
How late is too late to put out gypsum? With the recommendations of early bloom at approximately 30 to 45 days after planting, once peanuts get past that into the range of 100 days after planting, the majority of pods will have absorbed the proper amount of calcium or not and the outcome will be decided. Hopefully, this means pods filled with peanut kernels, no pod rots or “pops” and good germination the following year. PG
