Soil Testing 101
Soil testing is a very simple and inexpensive process (free besides shipping). It is very important to test your soil every two years to make sure you are properly fertilizing, liming, and managing your pastures. No matter what animals you have on your land, it is very important to regularly check your pH levels as well as levels of phosphorus, potassium and other nutrients.
So, how do you take a soil sample? First, you will want to get a soil sample kit, which you can pick up at your local Cooperative Extension Office. Sample an area of 10 acres of less per each box. Do not use a galvanized steel bucket when sampling because the zinc in the bucket will give you a false reading of the actual zinc levels in your soil. Only use iron or stainless steel tools and a plastic bucket. Also, you do not want to combine soils of different types or treatment histories. It is very important that you do not put the sample in a plastic bag. The lab needs to dry out your sample and when you put it in a plastic bag, you cause this process to take longer.
For each box, you will want to collect about 20 samples or more at various depths. For plowed soils, you will want to sample 0 – 8”; for no-till, sod, lawn and pastureland you will want to sample 0 – 4.” Once you have gathered your samples, you can mix them in a plastic bucket and then fill your box to the indicated line. A good tip is to fill in the information on the box before you put your sample in it. When filling out the information on the box, make sure you can identify the field the sample came from with the paperwork. The best way to send your sample to Raleigh is to put the sample boxes in a shoebox and tape the box up. The address of the lab is on your soil sample information sheet that goes up to Raleigh with your sample.
Soil test analysis can be used for cropland, pastureland, and even home lawns. However, when you are filling out your soil test information, make sure to correctly fill in the crop codes so the lab can properly analyze your sample. It is also important to provide the amount of lime applied in tons per acre as well as the year and month of the last application, if you made one within the past 12 months. In addition, it is helpful to the lab if you provide the first and second crop rotation so the lab can provide proper recommendations for a two-year cycle (since you are supposed to soil sample about every two years). When inputting your crop codes, you have many choices on the back of the sample information form. After some crop codes, there are letters, which mean: establishment (E), maintenance (M), and small grain (SG). It is important to write in the correct crop code followed by the correct letter so the lab can properly analyze your sample.
Your sample may take several weeks to come back with recommendations depending on what time of the year it is. Also, the lab no longer sends analysis results in the mail; they are only available online. Look for an email saying when your sample is ready. Be sure you fill in your email address on the soil information sheet. So, what does your soil analysis mean? There are many letters and numbers on your analysis and it can be a little overwhelming to interpret it the first time you see it. Don’t forget, your local Extension agent is able to help you read your analysis and help you determine the best recommendations for your particular pasture or field. There are several key points you should be aware of. First of all, take a look at your pH levels. They should be between 6.0 – 6.5. If the level falls below 6.0, that means your soils are too acidic and you should apply the recommended amount of lime per acre per application. If index levels for phosphorous, potassium and other nutrients levels are below 50, then you should refer to your analysis to apply the recommended amount per acre per application of that nutrient. If the levels are above 50, then the soil contains adequate amounts of that nutrient. However, as a general rule, if the levels are over 100, you do not need any more of that particular nutrient. Always refer to your specific soil analysis for particular recommendations based on each individual nutrient. For nitrogen, because it is variable in our North Carolina soils, the lab does not measure it specifically, but provides recommendations for nitrogen applications. Soil testing can greatly affect the productivity of your cropland and pastures, so it is an important step in proper management of your farm.
If you have any questions about soil sampling or would like to pick up a soil sample kit, please contact your local Cooperative Extension Office.
Article by: Margaret A. Bell, Extension Agent – Livestock, Craven & Jones Counties