Milk, because of the calcium it contains, builds strong bodies. Calcium also builds strong fruit, berries and vegetables. The secondary macronutrient has become the key to fruit quality as growers, consultants and researchers ponder how to get calcium moving into the soil and through the root, up the plant and into the fruit. A new source of calcium — calcium thiosulfate — is available that should help growers in their struggle to get that calcium molecule moving.
For Santa Maria, Calif., strawberry grower Dave Peck, strong berries are quality berries. Farming Manzanita Berry Farms alongside his wife, Diana, Peck says he'll grow for quality over quantity any day. For that reason, Peck pays more attention than most growers to getting calcium into his plants.
Biochemically speaking, calcium strengthens cell walls. It must be present for the formation of new cells, it helps synthesize proteins, and it transfers carbohydrates. Calcium helps tomato growers ward off blossom end rot, it keeps apples from turning to mush, and it's what helps Peck to improve the shelf life of his strawberries and maintain their size.
Pest control adviser Dan Maloney, with Western Farm Service, Santa Maria, says not all strawberry growers see fruit quality as a priority. They are quantity men, he says. Peck, on the other hand, wants to improve the firmness of his berries, and he's interested in hearing about any new products or technologies that might help him accomplish it.
Peck's strawberries are planted on 300 acres of “good to excellent” vegetable or row crop soils. They are typical valley soils for coastal California, Peck says, loamy sand to sandy loam with a slightly basic pH of 7.4 to 7.5 and a fair amount of calcium tied up as calcium carbonate. There are marginal soils in the area, but Peck says he doesn't plant on them. He leases all his ground, and he is always looking for more.
Peck tests his soil at least annually to make sure he doesn't miss something obvious. “We have always used, and strongly advocate the use of safe organic amendments and biological additives to manipulate the soil micro-environment in our favor,” he says.
To make the calcium in his soil available to the strawberries, Peck relied on gypsum. A valuable material, Peck nevertheless says gypsum requires a lot of labor because it dissolves slowly and “it's messy and it's inconvenient.” Maloney agrees. The gypsum does an “OK” job, Maloney says, but it is difficult to get it into solution. It is especially difficult to work with gypsum through drip irrigation because “inevitably you have problems with clogs.”
Chemical consultant Judith Hooper says that although there are chelated calciums available, there's always been a need for a soluble calcium that also can be easily taken up by plants. “There is calcium sulfate or gypsum, but it's very insoluble — around .2 percent and that is really very low,” says Hooper, who is president of Pima Research Co. of Tucson, Ariz.
Lot of gypsum
“Then when you get calcium sulfate into the soil, it gets bound up with different materials. In order to get enough calcium to the root of the plant, you've got to put on a lot of gypsum. The calcium sulfate molecule simply isn't very mobile.”
The search for the ideal soluble source of calcium — calcium thiosulfate — has been on for at least a half a century. Scientists could make it, but only in small amounts and at great expense. It existed, but not in nature and only in the lab. Over the years, millions in research dollars were spent by large companies seeking to produce calcium thiosulfate, because of its number of potential applications in a score of industries, including potable water and wastewater treatment and agriculture.
Five years ago, the feat was accomplished in Fresno in the laboratory and then in the manufacturing facility of a small company called Best Sulfur Products. Hooper says, “Best Sulfur is the first company, as far as I know, worldwide, that has succeeded in making this product consistently and on an industrial scale. I keep reminding them that they have accomplished the impossible. They've created an entirely new class of fertilizer — a soluble calcium with a low salt index, minus the nitrogen.”
Hooper, who serves as a consultant to Best Sulfur, says the calcium thiosulfate (brand name Thiocal) is both a plant nutrient and soil amendment. Its use makes highly soluble forms of 6 percent calcium and 10 percent thiosulfate sulfur available to plants while at the same time improving the productivity of soil by decreasing sodium, improving tilth and increasing water penetration.
A clear liquid, Thiocal can be applied through sprinkler, drip or flood irrigation. It may be sidedressed or applied by broadcast or band directly to the soil, and it mixes easily with most nitrogen fertilizers.
In agriculture, Hooper says the “big deal” about Thiocal is its solubility. A hundred times more soluble than gypsum, Thiocal is more likely to move through the soil profile and enter the root of the plant.
The calcium thiosulfate in Thiocal is a highly efficient compound, Hooper says. “We have calcium thiosulfate, calcium sulfate and the calcium EDTA complex of chelated calcium. Calcium EDTA complex and thiosulfate are both soluble, but the EDTA molecule is huge and bulky and difficult to get into the plant. With calcium thiosulfate and calcium sulfate, both of their molecules are biologically active in the plant and easily taken up by the roots.
The only downside to calcium sulfate is it's so insoluble. Getting it to the root can be a real problem.”
Peck read and heard about Thiocal before it was available on strawberries. When trials were set up for the product in Santa Maria, he made sure he was involved. Peck places a lot of emphasis on research and expends considerable resources on test plots every season. Since the mid 1980s, Peck has hired a small crew of specially trained workers just to manage the on-farm research each season.
As good, better
Peck says the Thiocal trial data showed it was as good as or better than the gypsum in getting calcium into the strawberry plants. He says the results were dramatic and significant. It would vary, but some weeks the production weights of the berries would increase from 10 to 25 percent over the gypsum application. Peck now uses Thiocal on his berries.
“I wouldn't say Thiocal gives you a 25 percent increase across the whole season,” Peck says. “But we see some weights with it, caused by accelerating plant growth that gives us probably a little bigger sized berry. Because we throw out so many berries that are small sized, if I can get a berry that grows 5 to 10 percent larger, it goes into the box instead of going into the ditch.
“A slight size increase can be real significant to us, especially in certain weeks where it gets real warm and our berries turn red at a smaller size. If they'll grow just a tiny bit larger and make our grade, then we actually get a lot more tonnage into a fresh box,” he says.
Peck irrigates by drip, moving water through the soil to leach salts and make sure his plant roots get adequate moisture. “All these things combined,” he says, “along with a good fertilizer program, the variety and the soil all work together. But Thiocal is a good drop-in replacement for gypsum that actually does a little more, it's economical and it's much more convenient because it's a liquid.”
While Peck acknowledges that he's added several new products to his production practices over the last several years, he contends that a larger number of people today “don't like dangerous chemicals applied to the environment” so that's one of the factors that he takes into consideration. But Manzanita Berry Farms “is not organic by any means,” says Peck, who maintains an extensive Web site that details his production practices as an educational tool for non-ag customers.
“We'll adopt any technology whether it's organic or chemical or new-age crystals,” Peck says. “As long as it meets our standards for being practical, profitable, safe and bio-rational, we'll find a way to fit it in.” Peck takes pride in integrating chemical, physical and biological components into a smooth and healthy farm operation.