Taking a Good Soil Sample
To receive appropriate lime and fertilizer recommendations for your soil, it’s important to send a good soil sample to the lab to analyze. Following are some tips for taking samples.
When to Sample
Soil samples taken in late summer and fall are better than those taken in winter through early spring because they come closer to representing the soil’s nutrient status as it affects crops. Avoid taking samples when soil is wet or frozen because it will be difficult to handle and mix them. Do not take soil samples immediately after applying lime or fertilizer; wait several months or even longer if the weather is dry.
Send samples to a soil testing laboratory well before you need the recommendations. Allow about three weeks for the samples to be processed and the results to be sent to you. Samples sent to the laboratory between March and June may take longer to process. Avoid delays by sending samples between July and December.
Where to Sample
Adequately assess the nutrients that plant roots may encounter in soils, at least five to ten randomly selected soil borings should comprise the composite sample submitted to the laboratory. Five to eight borings will be enough for small areas such as lawns and gardens. If a field is large, subdivide it into 10-acre sections and take at least 20 borings from each 10 acres (or about two to three borings per acre). In West Virginia, it is helpful to divide the field into distinct slope/soil classes and take borings within each class to make a sample. Different slope classes generally have different parent materials and different soils.
Exclude or take separate samples from areas not characteristic of the field, lawn, or garden such as wet spots, eroded areas, bare spots, back furrows, field edges. When the field has several soil types or crop conditions, take separate borings for each soil type or slope class and send a separate sample for each. No single sample submitted to the laboratory should represent an area larger than 10 acres.
How to Sample
Using an auger, shovel, or spade and a clean plastic pail or container, take small uniform cores or thin slices from the soil surface to the recommended depth (see the following paragraph). Gently crush the soil and mix it thoroughly, discarding any roots or stones. Do not send wet soil, but airdry it on a clean surface in a shady spot before mailing. Not only does wet soil cost more to mail, but your results will be delayed because the laboratory must still air-dry the sample. Do not heat the sample.
Send at least 1 cup (a handful) of soil to the laboratory in a plastic bag. (The WVU soil test mailer contains a sandwich bag to fill and place in the cloth bag.) Remember to include your name and address and other information on the sheets provided by the laboratory.
How Deep to Sample
Sample the soil to the depth in which your crops are or will be growing.
- Permanent pastures: Remove organic debris from the soil surface; sample the top 2 inches.
- Hayfields: Remove organic debris from the soil surface; sample the top 4 to 6 inches.
- Row crops: Sample the soil to the depth of tillage.
- No-till crops: Sample the top inch and take a second sample from the depth of 1 to 6 inches.
- Vegetable gardens and planting beds: Sample the soil to tillage depth.
- Lawns and turf: Sample the top 2 inches in established lawns and turf and the top 1 to 4 inches in new turf plantings.
How often to Sample
- Row crops and hayfields: Every one or two years or when crops are rotated.
- Permanent pastures: Every three to four years.
- Vegetable gardens: Every one or two years.
- Lawns and turf. Every three to five years.
Soil testing is the easiest and most reliable method of assessing a soil’s nutrient status. It provides a basis for recommending the correct amount of lime and fertilizer to apply for crops and pastures. Soil testing also allows an expert to predict the probability of obtaining a yield or growth response to lime and fertilizer application.
For more information about soil sampling, simply search for “taking a soil sample” through your Web browser. You’ll find several sites offering more instructions and photographs.