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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.
More calcium for larger-seeded varieties?
“The question growers wanted answered was, is more calcium needed for these larger-seeded varieties? The prevailing logic was that the larger the peanut size, the more calcium that’s needed. Our research, using gypsum, focused on the impact of calcium rate.
“At that time, our recommendation was for at least 500 pounds of soil test calcium in the pegging zone. If you didn’t have that much, the recommendation was for 1,000 pounds of gypsum on runner peanuts. For Virginia peanuts, which have large seed, everyone made an automatic 2,000 pound gypsum application.”
With the new large-seeded runner varieties, Harris says, “We thought maybe instead of 500 pounds of soil test calcium, they might need 750 pounds in the pegging zone. And if we didn’t have at least that much, then we’d pump the gypsum application up to 1,500 pounds.”
But, he says, “It’s a good thing we did the research, because that theory didn’t pan out. We found that it wasn’t necessary to increase our gypsum recommendation for the large-seeded varieties.”
For many crops, Harris notes, “We tend to focus on the Big Three nutrients: nitrogen, phosphorous, and potassium. As a legume, peanuts fix nitrogen and they are a very good scavenger of phosphorus and potassium. But, it is very important that we provide the needed calcium.
“Peanuts are also a pretty good scavenger of magnesium from the soil, as well as sulfur. Magnesium is usually supplied from dolomitic lime, although we’ve been moving away from that form to calcitic lime. If you apply gypsum, which is calcium sulfate, you’re applying sulfur, too.”
Peanuts don’t require large amounts of micronutrients, Harris says. “There are three we usually focus on. Boron is usually minimal in the soil, so we recommend a foliar spray — and it’s cheap.
“The other two, manganese and zinc, are very much tied to soil pH, but in providing these we need to watch out for manganese deficiency and zinc toxicity.”
There are a number of different gypsum products that can be used to get calcium into the pegging zone, he says. “A lot depends on which source you use, how you put it out, and the timing.”
Another option is lime, which is available in several forms, “but it needs to be used correctly,” Harris says. “Many producers think they have to use fine ground, high calcium lime, but that’s not the case — regular ground dolomitic lime will work fine, as long as you put it out correctly.”
There are liquid calciums, too, he notes, “But you need to be careful and know how to use whichever product you select.
There are also liquid limes and liquid gypsums, with various suspensions, but there can be handling issues with these that you need to be aware of.
“There are also some foliar products, but although peanuts will take up calcium through the leaves, they don’t move it down into the developing nuts, so spraying calcium on foliage isn’t going to help.