When it comes to analyzing character, soil is a lot like people: You have to dig beyond the surface.
South Carolina peach growers often complain of insufficient potassium levels in their sandy soils, said Clemson University emeritus professor Virgil Quisenberry. That’s true when testing topsoil, but in the subsoil, potassium levels are often high or excessive, Quisenberry told a group of peach growers at Clemson Extension’s peach update in Edgefield last month.
Inaccurate soil analysis leads to unnecessary fertilization.
A recent survey of a typical orchard soil revealed that proper soil testing can potentially save growers a minimum of $50 an acre most years, Quisenberry said.
South Carolina growers harvest more than 15,000 acres of peaches valued at more than $64 million, according to figures from the National Agricultural Statistics Service. That puts South Carolina second only to California in peach production.
Clemson is working to improve farming output, profitability and sustainability by improving the health of South Carolina soil. Clemson Extension agent and horticulture specialist Greg Henderson, for example, is leading a research and demonstration project to analyze the use of cover crops that can reduce erosion, reduce the level of nematode pests and recycle nutrients to the soil. He’ll begin planting cover crops at South Carolina farms this summer.
Improving soil health will benefit the environment too. Applying excessive fertilizer, such as nitrogen and phosphorus, is an environmental concern because they have been identified as pollutants to both ground and surface water, said Juan Carlos Melgar, a Clemson professor and fruit tree expert.
Over-fertilization also increases labor costs associated with pruning and thinning, he told growers at the meeting.
“Our management practices are really important,” Melgar said. “There is a limit to what you can apply. Applying excess nutrients does not increase yield.”
Applying the right amount of fertilizer requires a good test of the soil. Potassium often is lacking in South Carolina top soils because, like nitrogen, it moves readily through coarser textured soils typical of “The Ridge,” South Carolina’s predominant peach-growing region in the western counties of Edgefield, Saluda and Lexington. This gives the illusion in topsoil analysis that potassium is missing from roots’ diets, Quisenberry said.
Often, growers sample soil at six inches, but the typical root depth of a peach tree is four to 18 inches, Henderson said. He recommended using soil test results along with leaf analyses of trees in the field to balance a fertility program.
To maximize crop potential and profitability, Clemson’s Agricultural Services Laboratory conducts soil testing for South Carolina growers. County Extension offices across the state can provide the materials needed for a soil sample. Test results will help in decisions related to fertilizer and lime applications for commercially grown crops. It provides a scientific basis for maintaining optimum soil fertility levels and proper soil pH values to help attain maximum plant growth and economic yields.