UNH Cooperative Extension Soil Testing Procedures

Nutrient Analysis:

The choice of soil test methods used vary from state to state and it is important that the method chosen is reflective of soil, climate and research results conducted in the state or area you live. In New Hampshire we use a Mehlich 3 extractant which was developed in North Carolina in the 1980s. We changed to this extractant in the early 90s because of its ability to accurately extract nutrients and metals over a wide range of soil characteristics. In recent years it has also been found very useful in predicting environmental risk for nutrient movement, especially phosphorus.

This extractant is used to remove nutrients from your soil sample in an amount that is reflective of how much is available to the plant. Due to the volatile nature of nitrogen in the environment, nitrogen analysis is not preformed on basic soil samples. The amount of nitrogen needed by the crop is estimated based on the field history, certain soil characteristics, organic matter content if available, and the crop to be grown. For corn and certain vegetable crops, the soil nitrate test is also useful in determining the nitrogen required for the crop.

Organic Matter Determination:

For soil samples, a measured amount of soil is weighed and heated to 360 degrees C to burn off the combustible part of the sample. This represents the organic portion and is related to the amount of residual nitrogen available to the crop. For composts, the determination is similar but at a higher temperature (550 degrees C).

Textural Analysis:

This procedure determines the amount of sand, silt and clay along with the textural class as determined by the relative percentages of the three soil fractions.

This test is sometimes used by landscape architects, golf course superintendents, municipal park managers, and those who supply sand, soil and other mixtures used by these professionals in maintenance and construction activities. For further information contact your county office of UNH Cooperative Extension.

Soil Nitrate Test (PSNT):

This test procedure is used in several crops to determine if additional nitrogen is required to meet the yield goal for that specific field. The sampling and handling of these samples is very different than for the other soil samples submitted to the lab for analysis. The sampling depth is 12 inches and the sampling time is during the growing seaso base on the growth stage of the crop being sampled. Samples must be dried or frozen assoon as possible if accurate results are to be obtained. For more information contact your county Extension office.

Lead:

As part of the lead screening analysis for home grounds and gardens, we also provide (and sometimes recommend) a "Total Lead" analysis based on the US Environmental Protection Agency Method (USEPA) 3050/3051 plus 6010. This will provide a more accurate picture of the risk of lead contamination in your soil sample and whether you need to adjust your plans for gardening and use of the area.

Environmental Package:

This test measures the levels of six trace elements sorbed (held on) to the soil. The method used is USEPA method 3050/3051 plus 6010. This test can assist in monitoring soils that have been amended with residuals or other materials.

An individual soil test for lead can also be run when it is recommended by the lead screening test (part of the homes and grounds soil test package).

Plant Tissue:

Plant tissue analysis is a valuable tool in a crop management program. In NH, the major use of this analysis is in commercial fruit production such as apples, blueberries and strawberries. For more information contact your local county Extension office.