Soil Test Instructions

Soil sampling is a very useful tool if you are a homeowner or grow any of the following plants: turfgrass, ornamentals, fruits, vegetables, trees or houseplants. Soil sampling and testing is probably the most effective tool a homeowner has to help determine soil nutrient levels. Soil tests can help save the homeowner time and money, as well as encourage a healthy environment by reducing unnecessary fertilizer use.

Plants require sixteen essential nutrients to grow. Nitrogen, phosphorous and potassium are major elements and are required in relatively large amounts, whereas; others like calcium, sulfur, and magnesium are minor elements and required in moderate amounts. Other elements are required in extremely small amounts, but are just as important as the major nutrients. If any of the 16 essential elements are not present in adequate amounts, plant growth and development will decrease. On the other hand, if some of the same nutrients are present in excessive levels, they can be toxic to plants and be a source of pollution in the environment.

It is very important to take soil samples correctly in order to receive accurate recommendations. Homeowners are then able to apply the recommended amounts of lime and fertilizer for maximum plant production. Soil samples should be taken dry as excess moisture increases the drying time of the soil sample and makes soil boxes unreadable. Late summer or early fall is a good time to sample soil that adequate lime may be applied and can react with the soil by raising the pH prior to spring planting. Sampling may be done at any time of the year, although it normally takes longer in the fall (6-8 weeks) than in the spring (2-3 weeks). By sampling in the fall, sufficient time is allowed to make plans for the spring fertilizer applications.

The North Carolina Department of Agriculture (NCDA) Agronomic Division in Raleigh analyzes soil samples which are collected in North Carolina for FREE. The soil test results indicate the amount of lime and fertilizer formulation recommendations needed for the area sampled. The NCDA provides boxes and information.

Soil pH is a measurement of soil acidity. If soil pH is less than 5.5 or greater than 7.5 (for most plant material) some essential elements may not be available to the plant, while some toxic elements, such as aluminum, become available to the plant. Soil pH can be adjusted by applying granular or ground limestone to raise the pH or by adding sulphur to lower the pH.

To get a representative sample, the following steps need to be taken:

1. Decide the number of areas you want to have tested.

2. Obtain boxes and forms for submitting the samples. (One box for each area and one sheet for every 12 samples).
3. Collect 3-6 small samples, from within the top six inches (4 inches for lawns) of the soil, within the area of concern. It is important to take as uniform samples as possible (example: 2 inch diameter, 6 inches deep). The more small samples that are collected will give a better, more uniform representation of the area. A bulb digger or shovel takes very good samples.

4. As samples are collected, mix them together thoroughly in a plastic bucket, as a galvanized or tin bucket can contaminate the soil and cause inaccurate test results.

5. Discard all stones, roots, and debris. Transfer about a cup of soil from the small sample plastic bucket to the soil sample boxes proved by the NCDA.

6. Give each sample box a number or code that will indicate the area sampled, along with your name and address on each box.

7. Fill out the information sheet and bring it, along with your samples, to the local Cooperative Extension office.

Some Do’s and Don’ts of Soil Sampling