Soil Sampling Simplified

— Written By Bill Hanlin and last updated by JoAnne Gryder

soil samplingNow is an excellent time to take your soil samples and send them off to the North Carolina Department of Agriculture’s soils lab. If you send your samples in now, it only takes a couple of weeks to get your results back compared to 6 to 8 weeks if you wait until spring. Once you get your results all of the numbers may be a little confusing, but the form can be made a little simpler by just concentrating on a few numbers.

The first number I look at is the pH, which tells you how acidic or alkaline your soil is. Normal pHs for our area are around 4.5 to 5 and at these levels, most plants will not grow well. Most plants, besides blueberries and azaleas, require a pH of 6 to 6.5, and that may mean you will have to apply lime.

The amount of lime recommended will differ based upon whether the sample is from a homeowner or a commercial grower. For example if a homeowner recommendation may be to apply lime at 100 M, which means apply 100 pounds of lime per thousand square feet. For a commercial grower the recommendation could be 2 T or 2 tons per acre

The next couple of numbers to look at are the phosphorus (P) and potassium (K) indexes. Generally speaking any number below 50 means these nutrients are in low supply and should be a part of any applied fertilizer. The analysis report will recommend a fertilizer ratio based upon the P and K indexes.

The soils lab does not analyze your sample for nitrogen but they do make recommendations for nitrogen rates. These rates are based upon what you are trying to grow and, in my opinion, may be on the high side. Be careful about applying too much nitrogen as this may cause problems like increased disease pressure and poor quality fruit.

Right now the only cost for soil analysis done by the NCDA is the cost of mailing the samples off. Starting in November and running through the end of March the NCDA will charge $4 per sample. This is done to reduce the amount of samples that are sent to the lab during the winter, so get your samples sent off soon.