"Once we knew what he really needed, he was able to save several thousand dollars.” That’s the bottom line of a story relayed by Mark Green, District Conservationist for the Greene County Field Office of the USDA, about the benefits of testing the soil in pastures. This farmer had faithfully applied triple 17 fertilizer to his pastures for years without sampling his soil. When he got the results of his soil tests he found out that his pasture didn’t need any nitrogen or phosphorus, applying more would have been a waste of money.
Green said that soil testing is the only way to know what the soil in your pasture really needs to produce at its best. Without it, he said “you might as well throw your wallet out there.” In today’s economy especially, the information provided by a few simple soil tests can prove to be extremely valuable.
Green recommends that the best time to apply nutrients to pasture is in the fall and it is best to sample shortly before making the application. He recommends testing every three or four years unless the area has had big changes, such as big adjustments in nutrients or changes in use or crop. For instance, if you’ve been making applications to bring up the phosphorous levels a lot or if you changed a field from forest to pasture, you may want to sample every two years or so.
Soil testing is a relatively simple process, but there are a few things to keep in mind to make sure it is done right. As Green pointed out, the tests are only as good as the sample. Dr. Leo Espinoza, Soil Scientist with the University of Arkansas Division of Agriculture said that most often, questions about the results of a test are due to the quality of the sample, not the testing itself.
A few basics for collecting good samples are to collect “composite” samples of each area, keep good records of where and when the samples were taken and be consistent in sampling. A composite sample is prepared by grabbing several individual soil cores from across the sampling area and then mixing these cores together thoroughly to make one sample that represents the entire area.
Guidelines for Good Sampling
1. Select sampling areas that are easily managed as a unit – you can treat the whole area the same. Usually a sampling area should be 20 acres or less.
2. When grabbing individual soil cores, try to collect each core in the same way, to the same depth, and of the same size.
3. Each soil core should be approximately 6” to 7” deep. Discard the vegetation at the top of the core.
4. It is recommended that at least 12 to as many as 24 soil cores be collected from each sampling area.
5. Avoid taking soil cores in areas where livestock congregate, from manure piles, or other features that don’t represent the typical conditions in the sampling area.
6. Combine all the soil cores from the sampling area thoroughly. If necessary, the cores may be set aside to dry before mixing. After mixing, take a portion of the mixed soil and put it in the sample container.
7. Label each sample clearly and record the details of when, where and how the sample was taken. Marking sample areas and core locations on a map or aerial photo can be helpful.
A guide entitled “Soil Sampling Pastures” is available from the University of Missouri Extension and can be found www.ozarksfn.com, or from you local extension office. Green recommended using soil tubes or augers for best sampling results. Often these tools are available for loan at the local Extension or USDA/NRCS field office.
Samples can be submitted for testing to the Missouri Extension office or to private laboratories. Your local extension agent can help you select the best lab for your samples and budget. In the fall, test results are usually available within a couple of weeks. Make sure you allow for this time in your plans for pasture applications.
The immediate benefits of testing pasture soil are many, including getting the most efficient use of your fertilizer dollars, reducing the negative impacts of excess application, and getting the best production from your land. Dr. Espinoza suggests that even greater benefit will come from a long-term view of pasture soil management. As you build a history of soil test results, each from samples collected in a consistent manner, your ability to make wise decisions about what to apply on your pasture will grow as well as the grass you find there.
