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Don't Guess - Soil Test

The Soil Testing Laboratory, part of the Department of Crop and Soil Environmental Sciences and Virginia Cooperative Extension, has been in operation since 1938, when it was first established as a way to educate farmers about the need for adequate nutrients in their soil. Over the past few decades, its mission has expanded to also include education for homeowners and an increased focus on environmental topics.

“The soil testing program is focused on education,” says Jim Riddell, associate director for agriculture and natural resources for Virginia Cooperative Extension. “We don’t simply analyze the nutrients in the soil; we perform a complex analysis of soil potential and then we work with farmers to teach them how to use that data to improve yields and efficiency.”

There are hundreds of different types of soils in Virginia, each with its own unique characteristics. These hundreds of soils are organized into 43 soil management groups that combine soils according to similar characteristics such as in which regions they occur, how the soil was created, its texture, and others.

Fertilizer recommendations can be made based on soil management groups, but researchers at Virginia Tech felt that recommendations would be more accurate if they also were based on crop yield potential.

In the 1990s, soil and crop specialists developed the Virginia Land Use Evaluation System (VALUES). VALUES supplements the soil management group data with soil productivity data. Researchers learned that strikingly different soil types have essentially the same yield potential for a given crop due to their ability to retain water. In the VALUES system, soil management groups are organized into soil productivity groups based on similar yields for a given crop.

The VALUES system takes into consideration the specific crop to be grown, the crop yields that historically have been produced in that soil, slope and erosion information, and whether or not the field has a drainage system, among others. “By taking all of this information into consideration when making recommendations, we provide a soil report that gives farmers a wealth of information specific to their situation,” Riddell explains.

In 2007, the lab processed more than 56,000 samples. About 75 percent of those were from commercial farming operations, most of which come from Southeast Virginia, the major crop-producing region of the state.

“We have seen an increase in commercial samples as the price of fertilizer has gone up,” says Steve Heckendorn, laboratory manager. “It is important for farmers operating on small profit margins to know their soil needs exactly and to not over-fertilize for both cost and environmental reasons.” The inaccurate application of fertilizer can have a negative impact on the environment because excess fertilizer can find its way into water sources.

Heckendorn reports that about 20 percent of samples come from homeowners, a group that continues to increase its use of soil testing. Home lawns are a growing concern as a nonpoint source of water pollution in Virginia. Extension agents, Virginia Master Gardeners, the Virginia Department of Conservation Resources, and others promote soil testing for homeowners as a way of protecting the environment.

“Our motto is ‘Don’t Guess – Soil Test,’” Heckendorn adds. “Soil testing plays an important role in both maximizing profits for farmers and helping to protect the environment.”