Soil Sampling 101

— Written By Tracy Perry and last updated by Margaret Green

Soil samples are taken throughout North Carolina and they differ as far as the size of area sampled and the reason for taking the samples. Large-scale growers and homeowners depend on soil samples for nutrient management. After reading this article hopefully, you will have a newfound enthusiasm for soil sampling.

First and foremost where should you take samples? Every soil sample you submit for testing should consist of about 10 to 20 cores taken at random locations throughout one area. Keep in mind that each sample should represent one general location or soil type. For example, a front lawn should be one sample and the back lawn should be a separate sample. You can also collect samples from planting beds or from the drip-line of a tree.

Next on our list is how to collect a good sample. Collect your samples with stainless steel or chrome plated sampling tools and a plastic bucket. Avoid contaminating the sampling tools. Also avoid brass, bronze, or galvanized tools. Make sure that the bucket and sampling tools are clean and free of lime and fertilizer residues. Even a small amount of lime and or fertilizer transferred from the sampling tools to the soil can seriously contaminate the sample and produce inaccurate results. Before filling the soil box pulverize the cores and mix them thoroughly in the bucket.

At what depth should you take your sample? For fields where perennial crops such as fescue, alfalfa, and turf are being maintained, you should take samples to a depth of 4 to 6 inches. This is the depth at which a perennial crop’s lime and fertilizer needs are best represented. With all that being said, for crops that are being established you should sample to a regular plow depth of 6 to 8 inches. For areas in which field crops are grown, collect samples at the same depth that you would plow your field. For areas in which vegetable crops are grown collect samples to the same 6 to 8 inch depth, or to the depth that the field was plowed.

When should you take samples? Try to collect samples two months before planting time. You will then have the test report in time to plan your lime and fertilizer program. If you submit samples immediately after harvesting in the fall, you are likely to receive your results promptly because the laboratory workload is much liter at that time than in the spring.

How often should you take samples? It is a good rule of thumb to do a soil sample at least once every three to four years. Make sure that you include the correct code or codes on the sample information sheet. Make sure that the information on the soil box is filled out and the codes or code on the box is the same as the codes on the sample information sheet.

 Last but certainly not least, where do you get the sample information sheets and boxes? Also where do you take your samples when you have collected them? If you live in Franklin County, you can bring your samples to the North Carolina Cooperative Extension Center located at 103 South Bickett Blvd. in Louisburg, NC 27549. If you live in another county you can take your samples to that Extension office. You can also pick-up sample information sheets and sample boxes from your local extension office. If you live near or in Raleigh you can take you soil samples directly to the Agronomic Lab. The lab is located at 4300 Reedy Creek Road, Raleigh NC 27607. You can also reach the Agronomic Lab at 919-733-2655 or at www.ncagr.com/agronomi.

I realize that this was a lot of information to consume, so if you should have further questions please do not hesitate to contact the Franklin County Office at (919) 496-3344.

Soil Sampling

Tracy Perry

Agricultural and Natural Resources Technician

Franklin County Cooperative Extension

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