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Calcium In The Pegging Zone

Should you use gypsum, lime or liquid calcium?

By Glen Harris,
University of Georgia Extension
Soil Scientist
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By now, every peanut producer should be aware that the new large-seeded runners that will be grown predominently in 2010, such as Georgia 06G, Florida 07 and Tifguard, need more calcium.

Based on field research in Georgia and Alabama in 2009, it looks like the traditional application of 1,000 pounds per acre of gypsum at bloom still works well for these cultivars. In fact, there seemed to be a slight decrease in peanut yields in a few cases when 1,500 pounds per acre of gypsum was applied, which may be due to the extra calcium causing a hidden potassium deficiency.

Deficiencies Will Show
The new large-seeded cultivars are going to need gypsum more often, even when the pegging zone soil calcium is above 500 pounds per acre, right? Well, not necessarily.

Based on the same research trials mentioned above, it appears that the 500 pound-per-acre calcium level in the pegging zone also holds up pretty well…with one exception. Both Georgia 06G and even Georgia Green responded to gypsum applications up to 1,000 pounds per acre on an irrigated deep sand at the Stripling Irrigation Park in Camilla, Ga., even when the pegging zone calcium was 950 pounds per acre.

So, if the recommendations didn’t change, these new cultivars really don’t need more calcium, right? Wrong again!

There is no doubt that these larger seeded runners have a higher requirement for calcium and are more susceptible to calcium deficiencies. In many situations where gypsum was not put on Georgia Green and you got away with it, you won’t get away with it on a large-seeded runner like Georgia 06G.

Gypsum: From Tower To Field
Gypsum, which is calcium sulfate and is also known as landplaster, applied during early bloom is the traditional way to provide calcium to the peanut pegging zone. There are a number of good gypsum materials currently on the market, and your purchasing decision can be made based on price, “spreadability” and availability to your area.

Recently, the use of “smokestack” gypsum has become more common. This material comes from coal-burning power plants where lime (calcium carbonate) is used to “scrub” sulfur out of the smokestack emissions, and the end result is gypsum or calcium sulfate.

Some producers have expressed concern over the possibility of heavy metals in these types of materials. However, the laboratory analyses I have seen of these materials showed very low and safe levels of any possible contaminants.

Also, even though smokestack gypsums start as lime, the material is converted to gypsum. Like any gypsum, it does not raise the pH of our surface soils in the Southeast. It is the carbonate, not the calcium, in lime that raises the pH, and only lime can raise the pH in the “plow zone” of our soils.

Timing Your Liming
For the last 10 years or so, the “lime” method of providing calcium to the pegging zone of peanuts has become more popular. This is probably due to the fact that lime is less expensive per ton than gypsum. However, if you use the lime method, timing is everything.

Make sure to apply the lime prior to or at planting. Also, do not deep turn the lime. Scratching it into the pegging zone with tillage after deep turning or before bedding is recommended.

What kind of lime is best? Some people seem to think that you have to use a finely ground, “hi-cal” or calcitic lime when using this method. The original research on this method was actually conducted using regular-ground, dolomitic lime. Dolomitic limes must contain at least six percent magnesium; calcitic limes contain very little, if any, magnesium.

It is true that the calcium in lime is not as soluble or available as the calcium in gypsum, which is why you can’t wait until the bloom stage to put lime on the peanut crop. However, there are enough “fines” even in a regular-ground lime to react by peanut bloom.

 

Calcium Recap:

The Goal: Provide enough calcium to the peanut crop to reduce “pops” and maintain yield, grade and germination for seed peanuts.

Gypsum:
• Can be purchased based on price, “spreadability” and availability

• Smokestack gypsums show low, safe levels of contaminants, heavy metals

• Does not raise soil pH, even types converted from lime to gypsum

Lime:
• Less expensive per ton than gyp-sum

• Must be applied prior to or at planting

• Do not deep turn, but scratch into the pegging zone

• Regular-ground, dolomitic lime is fine to use

Liquids:
• Foliar calciums not recommended; calcium does not translocate from leaves to pegs

• Liquid lime and gypsum are effective at correct rate

• Pivot-applied calcium being studied; water rate makes it soil applied
 

What Are Liquid Calciums?
Liquid calciums is generally a confusing category because there are subcategories as follows: 1) liquid lime and liquid gypsum, which are just fine lime or gypsum in a suspension with water; 2) soluble liquid calcium sources such as calcium chloride and calcium thisosulfate that are designed to be applied at 10 to 30 gallons per acre behind the presswheel at planting on dryland or through a center-pivot irrigation system; and 3) “foliar” calciums recommended in the one quart per acre range with 10 to 15 gallon per acre final spray volume.

First, let me make it clear that “foliar” calciums are not recommended by UGA on peanuts since the material does not supply near enough calcium, and the calcium does not translocate through the leaves to the developing pods.

Liquid limes and gypsums can be effective if applied at the correct rates, but you end up hauling a lot of liquid around.

Pivot Application Being Studied
Calcium chlorides and calcium thiosulfate applied through the pivot are currently being researched because it is true that the calcium in these sources is even more soluble than the calcium in gypsum. It is possible that the correct rate of these materials applied through the pivot at the right timing (i.e. when the peanuts in the pegging zone are absorbing calcium) may help increase grade and germination on peanuts produced for seed.

For clarification, even though these materials are applied through a pivot, it is not a “foliar” calcium since an acre-inch of water is roughly 27,000 gallons of water. Compare that to a true foliar application where only 10 to 15 gallons per acre are used. Calcium applied through the pivot is really soil-applied.

Regardless of whether you take a pegging zone sample and it doesn’t call for additional calcium, or whether you use the lime method or apply gypsum, the goal is to provide enough calcium so that your crop does not have “pops” and the result is a decrease in yield, grade and germination for seed peanuts.

PG

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