How to Test Soil for Farming
Just as it is important to test your livestock for disease, it is also in your best interest as a farmer to test your soil before fertilizing and planting your crops. On the surface, one soil sample can look similar to another, leading one to believe that they contain the exact same things when they are made up of a completely different composition of nutrients. The key to successful farming is to find a healthy balance of the necessary nutrients of calcium, copper, magnesium, manganese, phosphorus, potassium, sodium, sulfur and zinc to create optimum growing potential. In order to find this balance, a soil test can be done to find out your nutrient levels, pH, humic matter (organic content of decayed vegetation) and exchangeable acidity. The results you get from the test can help you to plan out your crop rotations each season and decide what kinds and how much fertilizer and lime you’ll need to apply to produce strong, healthy plants while minimizing your nutrient run off into surrounding bodies of water.
Before collecting soil samples
Depending on your operation and your desire to cater to individual plants or types of plants, soil testing is suggested for every three to five years for gardens but should be done annually for large farming operations. Soil samples are best taken in the late summer-early fall time frame to give ample time for application of necessary fertilizers and nutrients. Before you gather your samples, draw up a plan or map of what areas you’ll be sampling. Within those areas, mark the spots where you plan to take the sample; larger areas may need between 10 and 15 different samples to mix and smaller areas, like flowerbeds, may only need between four and six. You’ll also want to decide if you want a more in depth analysis of your soil through a lab testing or if you’re comfortable with an at home method. Regardless of your choice, make sure to review directions for taking the samples and packaging to achieve the most accurate results. In both cases, you’ll need a spade or soil probe, clean buckets or plastic bags, and something to record your progress with.
After you’ve completed your planning and preparation for taking your samples, it’s time to get your hands dirty and dig in! Equipped with your map layout of where you’ll take your samples, find your first sample site and clear off any organic matter covering the ground, like leaves and mulch. Use your spade or soil probe and dig down six to eight inches for crops and flowers or eight to twelve inches for trees and remove about a pint of soil per sample site. Place the soil into a clean bucket or plastic bag and label both your sample and its corresponding point on your map. After taking all the cores from your first area, combine them into a bucket and mix them all together until the soil no longer contains large chunks. Label this bucket and set it aside while you repeat the process with any other areas you wish to test. After you have all of your representative samples from your different areas collected and labeled, package your soil to be shipped out to the lab or follow the directions on your at home kit to begin the testing procedure.
Where to find a Soil Testing Lab
If you’re not sure an at home test will work for you, there are many different resources you can tap into to find a lab that will run the tests in your area or be shipped out. Contact the following resources for more information on soil testing:
- The United States Department of Agriculture
- Local Cooperative Extension Offices
- Your State’s Department of Agriculture or Agronomics
- Local agribusinesses that supply farming needs
- Other crop producing farmers in your area
How to interpret soil test results
One of the first things you’ll see when you look at your soil results should be the soil pH as a number on a scale from 0-14. If your soil’s pH is less than seven, it is considered acidic, while a number greater than seven is considered alkaline. Most plants grow best at slightly acidic pH of 6.1 to 6.9 however some plants, like azaleas and blueberries, grow better at more acidic pH levels between 4.9 and 5.5. If you find your soils’ pH too far skewed in one direction, lime can be added to raise your pH or sulfur to lower it. Before making any additions to your soil in terms of fertilizer or nutrients, make sure to calculate how much of each element should be added per square foot for smaller gardens or per 1,000 square feet. Be sure to reach out to your local extension office or gardening center for help deciphering your results.