“I had GPS and soil sample data,” Hardy said. “I used the previous year’s yield map and the soil sample information from the spring. It worked for me. Since then, I’ve continued to find it more convenient to sample in spring.”

Spring sampling can be effective for conscientious farmers, Farrer said, because it gives them extra time to look at data and compare prices for lime and fertilizer. “They can be ready to buy when the market is most favorable,” she said. “On top of that, if they can move away from annual sampling, then they save additional time and money.”

Hardy confers with Farrer if he has concerns about using fertilizer recommendations from an existing report.

Soil phosphorus levels don’t change very rapidly, and nitrogen recommendations are based on the crop to be grown, not on soil test measurements. Potassium levels, on the other hand, can be significantly depleted by crop uptake or leaching. 

In cases of extreme or unusual weather, such as severe drought or periods of excessive rain that promote leaching, growers are advised to consult with a regional agronomist or other agricultural adviser about revising existing lime and fertilizer recommendations. If the crop is the same and weather is typical, then recommendations on NCDA&CS soil reports are generally reliable for two years.

As harvest approaches, growers across the state will automatically begin the process of soil sampling for next season.

Those who use GPS technology annually are encouraged to sample judiciously, using the service primarily for preliminary identification of problem areas and establishment of baseline information on field variability.

Growers who do not use GPS are advised to concentrate on fields most vulnerable to changes in fertility, for instance those with sandy soils.

In either case, it is beneficial to submit samples as early as possible. Sturdy shipping containers that can hold up to 36 soil sample boxes are available free of charge from the Agronomic Services Division. Its website also provides a bar-code tracking feature. When bar-coded packages arrive at the lab, senders receive e-mail notification of successful delivery.

For some growers with recent soil reports, fall sampling may not be necessary. Soil information already on hand can be used to make management decisions as long as relevant site-specific factors are considered.

Consultants can offer guidance on the development of nutrient-management strategies to optimize profitability and protect natural resources.

To find contact information for NCDA&CS regional agronomists, visit www.ncagr.gov/agronomi/rahome.htm or call J. Kent Messick, Field Services Section chief, at 919-733-2655. Agronomists can advise on all aspects of sampling and sample submission, including bar-code tracking of packages.