Understanding the Soil Test Report

A soil test takes a "chemical inventory" of the soil and determines its ability to supply the essential elements in the right proportion and adequate amounts throughout the growing season for a specific crop. The Soil Test Report indicates the calculated amounts of lime and fertilizer needed to supplement the existing nutrients in the soil so that maximum crop growth can occur.

The two things on the Soil Test Report that are of importance to home gardeners are the recommendations made for 1) lime and 2) fertilizer for the crops the homeowner wishes to grow. Many complex calculations are necessary to determine these recommendations, which are based on the values listed under "Test Results," but they need not concern most home gardeners. A sample Soil Test Report is included below.

pH is important to home gardeners because most plants thrive best within the 6.0 to 6.5 range, in-cluding lawns, vegetables, fruits, most shrubs, annuals and perennials. "Acid-loving" plants such as azaleas and rhododendrons prefer a pH of 5.0 to 5.5. It is important to realize that the pH scale is logarithmic, meaning that a pH of 5.5 is ten times more acid than 6.5 and a pH of 4.5 is 100 times more acid than 6.5. The neutral point is 7.0; above this point the soil is classified as alkaline. The natural pH of the Cumberland County area is 4.5 to 5.3, too acid for most crops, and so soils should be tested each 2-3 years for acidity as well as fertility. The pH is shown under "Test Results" for each sample.

Lime: The pH determines how much lime is required. The amount will be shown on report as "1 M" meaning 1 lb. per 1000 sq. ft., so 20 M means 20 lb. per 1000 sq. ft., etc. You must adjust the recommendation to the size of your garden plot. Lime may be applied at any time of the year; it takes several months for the pH of the soil to be altered. If your Soil Test Report recommends more than 60 lb. per 1000 ft. for surface application to lawns, it is advisable to divide the total amount into two applications, applied 4-6 weeks apart. Dolomitic limestone is recommended. Powdered lime should be used for incorporation into the soil, but either powdered or pelletized may be used for surface application.

Fertilizer: Shown on the sample as "20 lb. of 5-10-10 OR EQUIV PER 1000 SQ. FT." Or perhaps your report might say 10-5-5, which means a fertilizer containing 10% Nitrogen/ 5% Phosphorus/5% Potassium. If you cannot find the exact formulation recommended in the report, use the one that most nearly fits the Nitrogen-Phosphorus-Potassium ratio recommended. If your report suggests using a single nutrient only:

Nitrogen:	use Ammonium Nitrate. - 3 lb/1000 sq. ft.	34-0-0
	or Blood meal - 8 lb/1000 sq. ft.	12-0-0
Phosphorus:	use Superphosphate	0-18-0 or 0-46-0
Potassium:	use Potassium Nitrate; contains 13% Nitrogen also	13-0-45

When to expect your Soil Test Report:

Soil samples may be taken any time of year that the soil is reasonably dry. However, the length of time before receiving your results varies from two weeks in light periods to two months during late winter through spring, the busiest time for the lab. Testing is performed at the NC Department of Agriculture laboratory in Raleigh. We at the Cooperative Extension Service in Cumberland County have no control over the testing or reporting process, so there is no point in calling us to ask when your results may be expected. If you have any questions about interpreting your Soil Test Report, call the Cooperative Extension Service at (910)484-7156