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Calcium requirements heavy in peanuts

The recent growth of South Carolina’s peanut industry, especially the large percentage of Virginia-type peanuts grown, has created a big need for calcium, commonly referred to as land-plaster.

Santee-Cooper power plants, which provide electricity to about 2,000,000 South Carolinians, many of them in the heart of the state’s peanut producing belt, has stepped up its efforts to supply calcium, in the form of gypsum, to peanut growers.

In the process of generating electricity Santee-Cooper burns coal, which contains sulfur. To adhere to Federal clean air policies, the company has to capture the sulfur, rather than emitting it into the atmosphere.

They clean up the sulfur by capturing it as sulfur dioxide. They grind up limestone to create a slurry. When the gas comes in contact with the slurry it produces calcium carbonate in the form of gypsum.

Prior to the dramatic growth in South Carolina’s peanut industry, most of Santee-Coopers calcium carbonate was left in slurry form and sent to landfills. In 2004, they obtained a license to manufacture and sell the solid form of calcium carbonate into the agricultural market.

“It’s been a good thing for peanut growers in the state and it’s been a good thing for the people of South Carolina,” says R.M. Singletary, vice-president of operations for Santee-Cooper.

“We now make about a million tons of gypsum from our combined power plants. Most of it goes into wallboard, but more than 50,000 tons goes into the agriculture market, almost all that for peanuts,” Singletary says.

Up to 80 percent of the South Carolina peanut crop is made up of Virginia type varieties.

In runner and Virginia type peanuts calcium is by far the most critical nutrient for achieving high yields and grades. Low levels of calcium causes several serious production problems, including unfilled pods (pops), pod rot disease, poor grades, darkened spots in the seed and poor germination.

Virginia-type peanut varieties are less able to take up adequate calcium than runner and Spanish types. This may simply be a matter of pod size, since there is less surface area on larger pods per unit weight of nut. For runner peanuts, the critical soil test level is 600 pounds of calcium per acre, but on Virginia type peanuts, yield and grade response occurs even at a soil test of 1,000 pounds of calcium per acre.

Clemson University Peanut Specialist Jay Chapin says gypsum from the Santee-Cooper plants has consistently performed well in tests.

In 2007 tests, best results came from applying gypsum 33 days after planting, but were only marginally better than at-planting and 13-days after planting treatments. The three gypsum application timing treatments all increased yield by over 500 pounds per acre, compared to check plots.

Though similar in terms of quality, the later-applied gypsum produced 2 percent to 3 percent more extra-large kernels than the other two application times and over 10 percent more than check plots. The later application also produced $15-$20 more than the other two application times and nearly $200 per acre more than the check plots.

The 2007 test also compared four sources of gypsum: the Santee Cooper product, mined gypsum, a citric acid by-product, and recycled wallboard. When applied at the same actual rate of calcium, all four products performed equally well.

In 2008, Chapin compared the Santee-Cooper gypsum to a foliar-applied product and varying application times. Delaying application until 50 days after peanuts were planted caused significant yield and grade reductions relative to application zero, 15, or 35 days after planting, and all the solid gypsum applications were better than the foliar-applied product.

Chapin said there are two take home messages: Use the most economical gypsum source you can spread conveniently, and it’s okay to be a bit earlier than the ideal 35 DAP, but don’t be late.

The Southern company recently undertook a study in the Southeast to determine the need for agriculture-grade gypsum for a number of crops, including peanuts, cotton and vegetables. In general, all crops appeared to benefit from the soil-amending qualities of calcium and sulfur in the gypsum products.

However, peanuts remain the major crop in the region in which calcium from gypsum is used to benefit both yield and quality.

In North Carolina, researchers compared the use of crushed gypsum boards to conventional land-plaster in an on-farm test. The test plots were shown at the Northeast North Carolina Ag Expo back in August and there was no visual difference between the two treatments.

The Santee-Cooper gypsum has been an on-going and economical source of land-plaster for South Carolina peanut growers since the resurgence of the crop in the early 2000s.

Landy Weathers, along with his brother Hugh Weathers, began growing peanuts in 2004 as a means of rotating grazing crops for their dairy operation. They were among the first peanut growers in the state to use the Santee-Cooper gypsum on peanuts.

Gregory is the primary variety for the Weathers brothers, though they grow a few acres of other varieties. All Virginia-type varieties require land-plaster, or some source of additional calcium, but the large-kernel Gregory variety has high calcium needs. Always inventive, the Weathers brothers used sludge from the nearby Santee-Cooper electric plant, with good results.

Now going into their sixth year of peanut production, Hugh Weathers, who is now Commissioner of Agriculture in South Carolina and his brother agree the use of Santee-Cooper gypsum has played a small, but key role in their success with peanuts. The demand for Santee-Cooper gypsum has grown with the growth of South Carolina’s peanut acreage. To better meet the growing demand in 2009, the company has changed some procedures for acquiring land-plaster.

“We intend to offer gypsum to farmers more efficiently by assigning each farmer an account number. The farmer can call a direct phone line and arrange for picking up the gypsum. Minimum purchase will be 50 tons and we will have a person on-site to be sure trucks are loaded in a timely manner,” Singletary says.

Farmers interested in purchasing gypsum for the first time from Santee-Cooper can phone the main number at 1-843-761-8000. Existing customers will receive a card from the company with the ‘gypsum line’ number, Singletary adds.

Peanut farmers throughout the upper Southeast may have similar access to power plant-produced gypsum. In today’s economy, with peanut contract prices uniformly down from 2008, saving money on the little things may mean staying in business.


TAGS: Peanuts
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