Sid Cayton farms an array of soils in Beaufort and Pamlico counties in North Carolina. In 2005, he became concerned about low yields with no-till corn he was growing in rotation with wheat and soybeans on peaty, organic soil.

Cayton saw that situation improve with the advice of Kent Yarborough, a regional agronomist with the North Carolina Department of Agriculture and Consumer Services’ Agronomic Division.

In 2007, yield on that no-till corn tract was at least 20 bushels per acre higher — a fact Cayton credits to a more conscientious approach to soil sampling.

“I’ve farmed my entire life,” Cayton said. “Here in Aurora, fields can stretch as far as the eye can see, and I was used to having soil samples represent an entire 15-acre field. It was all organic soil. It didn’t seem like there could be much variation under the circumstances.”

Organic soils are known for their low pH, and certain organic soils do not hold phosphorus well. Despite following soil test recommendations, Cayton had been having trouble getting soil pH and phosphorus levels up to where they needed to be. When the recommendations on his soil test report advised him to contact his regional agronomist, Cayton followed through.

Yarborough was quick to respond to Cayton’s call. As a member of the NCDA&CS field services staff, Yarborough’s job involves helping growers use the state’s agronomic testing services appropriately and effectively.

Yarborough sampled on a much smaller grid, with each sample representing three to four acres instead of 15. Sample collection was more intensive and time-consuming, but the effort proved to be worthwhile. The difference in the test results was dramatic.

Yarborough’s samples revealed a large disparity in soil pH values and phosphorus levels within the problem area. Since Cayton’s earlier samples had represented large areas, the recommendations he received were aimed at treating an average of the overall nutrient problems. The variation revealed by Yarborough’s samples, however, made it clear that the previous recommendations would not have been able to correct nutrition in the severely deficient areas and could have led to excessive application in other areas.

The new soil tests provided a much more detailed picture of pH and nutrient levels.

The results gave Cayton the information he needed to begin planning a precisely targeted application strategy. After reviewing the farm’s standard fertilization practices, Yarborough suggested other changes as well.

The problem fields had been managed as no-till for about 10 years. To minimize traffic on this land, Cayton was in the habit of applying lime and fertilizer once every two years. He planned each application to last for three consecutive crops — corn, wheat and soybeans.

“Application of fertilizer once every two years on certain organic soils may not be the best approach, especially when there is an ongoing fertility problem,” Yarborough said. “Maintaining the correct soil pH enables the crop to use applied fertilizer efficiently.”

In some areas, pH was so low soil test recommendations were calling for two tons of lime per acre to achieve a target pH of 5.0. There was no way to surface-apply that much lime and get effective results. Cayton decided the best way to adjust pH would be to disk the lime into the soil and then mix it in thoroughly with a surface cultivator.

“We saw improvement in the wheat crop the following spring,” Yarborough said. “The real reward, though, showed up in the corn yield.”

Comparison of the 2005 and 2007 seasons is difficult because they were so different; 2005 was an average year whereas 2007 was exceptional for most growers in Beaufort County. In spite of the statewide drought, this area got rain at just the right times.

“Corn yield on my organic land was about 35 bushels higher than in 2005,” said Cayton. “Good weather was a major factor, but I feel certain that Yarborough’s meticulous approach to soil sampling was responsible for at least 20 bushels of the yield increase.”

Based on Yarborough’s advice, Cayton has adopted a new approach to managing his farm. He plans to continue taking soil samples on a smaller grid. He is going to collect samples from good- and poor-yielding areas of his organic soils for comparison every other year, and he intends to fertilize each crop individually instead of shooting for carryover for the subsequent crop.

“It takes more time, but I’m convinced it will be worth it in the long run,” Cayton said. “I should be able to save money by spoon feeding nutrients to the crop. I’ll apply less fertilizer, but the crop will actually get more since there will be less likelihood of leaching. This year, my crops were more uniform in the fields Yarborough helped me with.”

The NCDA&CS Agronomic Division has 13 regional agronomists available to visit growers, evaluate suspected problems, give advice on sampling, liming and fertilization, and help identify and manage nematode problems. Go to www.ncagr.com/agronomi/rahome.htm for more information.