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While peanut plants can absorb calcium from the soil, “They can’t translocate it down into the developing nuts — that’s why it’s important that the calcium has to be available in the top three inches of the soil," says Glen Harris, University of Georgia Extension fertility specialist.
ADEQUATE CALCIUM in the top three inches of the soil profile is critical for optimum development of peanuts.
Availability, cost, handling considerations
“If you have adequate calcium sulfate, most of these products are very effective, and you can base your choice on availability, cost, handling, etc. As for the gypsums, I’ve not seen a bad one yet.”
For timing of gypsum applications, Harris says, “Our recommendation is to apply gypsum at early bloom, about 35 days after planting. If you’re applying calcium chloride or calcium thiosulfate through a center pivot, this should be done 60 to 90 days after planting.”
Solubility of calcium in the various products is key, he says. “The reason we apply lime at planting is because the calcium carbonate in lime is less soluble than the calcium in gypsum, which in turn is less soluble than the liquids.
“So, we apply lime at planting to give it enough time to become soluble. If you apply it at bloom time, it’s too late; so we apply gypsum, which is more soluble. If for some reason you need to add some more calcium at the 60-90 day period, you can use one of the liquid products.”
Research trials have shown, Harris says, that lime recommendations should differ for dryland and irrigated peanuts. “We were recommending lime at planting for both dryland and irrigated peanuts. But our research data showed lime at planting, in a normal year, does not perform as well as gypsum for dryland peanuts. So, one of our new recommendations for dryland peanuts is to use gypsum at bloom time, not lime.
“And we’ve found that adding calcium chloride in irrigation water is not as effective as gypsum — but it will get some calcium into the peanuts.
“There’s a new liquid lime we tested for the first time last year, which should work well in center pivot applications. It raised pH very quickly and held it, and we’re going to be studying how effective it is at getting get calcium into the nuts.”