If you're a small farmer, homesteader or hobby farmer who is growing crops in the soil, you will want to get your soil tested by a laboratory. Soil testing will allow you to amend your soil to be more productive. It will help you select the right kind and amount of fertilizer and liming material. There is technique involved in selecting a good soil sample for your test. Let's find out when and how you should test your soil.
When to Test Your Soil
For perennial crops - orchards, pasture, Christmas trees, alfalfa, grass seed, and so on, you should test your soil before planting, preferably at least several months before planting so that you have time to lime the soil and have it mix with the existing soil before planting your crop. Lime reacts slowly with the soil, so having time before planting is important. To maintain your soil, test every three years after planting (except for timber or Christmas trees, which don't need retesting). For established fruit trees, berries, or grapes, use foliar nutrient analysis instead of soil testing. For annual crops, such as vegetables, test your soil every spring before planting for the season.
Where to Have Your Soil Sample Analyzed
Your cooperative extension service is a great place to ask about soil tests. They have a list of laboratories that perform soil sample testing. After choosing a lab and before taking your sample, call the lab and request a list of tests available and the cost, as well as information on how to prepare your sample. You should have this paperwork in hand before taking your soil sample. Prepare your sample according to the instructions. Usually this means putting your samples in plastic baggies that zip closed, labeling them with specific information, and bringing them to the lab with your payment. Make sure to number each sample and keep a record of where you took the samples.
What Soil Tests to Request
You may be wondering what exactly you need to know about your soil. The standard tests are the following:
- Organic matter
- Soil pH or acidity
You may need some additional tests and you can ask your extension office what they recommend.
How to Take a Soil Sample
Taking a good soil sample is key to getting good results from your soil testing. Each soil sample should represent one type of soil or one soil condition - for example, pasture versus vegetable garden, or upland versus lowland. Take separate samples from each area.
- Sample where the crop will be planted. If you are using raised beds, sample the soil in the beds rather than in the paths between them. Take small subsamples, 15 to 20 of them, from different locations within the sampling area.
- Sample a typical area. Avoid unusual areas, like where manure was piled, or where you know there is a band of fertilizer.
- Don't contaminate your sample. Use clean tools to dig your sample, making sure there is no fertilizer residue or other contamination on them. Don't use galvanized, brass, or bronze tools to collect samples if you are testing for micronutrients, as these materials will contaminate your sample.
- Sample to the proper depth. The proper depth is the depth of the roots of your plants. For most annual and perennial crops, this means six to nine inches below the surface.
- Mix your sample. Place all the subsamples from one area into a clean container and thoroughly mix them together.