1. Why use the LSU AgCenter Soil Testing and Plant Analysis Laboratory (STPAL)?
The LSU AgCenter STPAL offers a variety of soil tests and plant tissue diagnostic tests to meet your planning needs for profitable production. Fees charged at STPAL are cheaper than any commercial laboratory on similar tests. The STPAL offers adequate fertilizer recommendations based on latest results of Louisiana-specific research. We do not recommend fertilization that wastes your money and may cause adverse environmental consequences. In addition, STPAL uses a modern quality assurance program to improve its analytical process for accuracy and efficiency. The STPAL is the only Louisiana laboratory that participates in the well-recognized North American Proficiency Test (NAPT) program.
2. How do I take a soil sample?
In general, soils that differ in appearance, crop growth or past treatment should be sampled separately, provided the area is of such size and nature that it can be fertilized separately. For each sample, collect soil from 15-20 places in each sampling area in a zigzag fashion to make a representative sample. Mix the 15-20 subsamples thoroughly in a clean bucket before filling a sampling carton or zip lock bag to be mailed to the Lab. One soil sample should represent no more than 10 acres. Avoid sampling directly in the fertilized band. Proper sampling depth will be key to have a representative soil test report and it should be 6 inches.
3. When and how often do I need to collect soil samples?
You need to take soil samples every 2-3 years to ensure that you update field fertility conditions. We recommend that you collect and submit samples 3-5 months before your projected planting date to ensure that you have plenty of time to plan your liming and fertilization program for the upcoming season.
4. How much sample do I need to send to the Lab for testing?
For soil samples, you need to send in between ¾ to 1 pint of soil for each sample to the Lab for analysis. We need a minimum of 4 oz. of water for the irrigation/aquaculture water test. If you are submitting a potting mix sample, at least 1 pint is needed.
5. What happens if I do not have an LSU AgCenter sample carton/box?
You can contact your parish extension office or one of our local distributors for paper bags. Or you can pick paper bags up at the Soil Lab on campus at 122 M.B. Sturgis Hall (located on the corner of Tower and Highland).
6. Do I need to state the specific crop to be grown for fertilizer recommendation?
Yes. It is important to specify what crop you plan to grow so a correct recommendation can be generated for your sample. The back sheet of the Soil Test Request Form lists available crops. A maximum of three crops per sample.
7. What should be the condition of soil sample I mail to the Lab?
In general, you need to send a soil sample that is dry as possible. If you send samples that are very wet, you may consider using a plastic bag instead of a paper bag. Very wet soil samples can damage the paper bags and cause a loss of your sample in delivery process before reaching the Lab.
8. What form of payment should I use for tests?
You can enclose a money order or check for payment made out to SPESS-STPAL. You may also use either a VISA or Master Card credit card and pay by contacting the Lab at 225-578-1219. Or cash.
9. Is it OK to submit the soil sample through nursery or hardware stores?
Soil samples submitted through local nursery stores where they offer such service is not recommended. For quicker turn-around, please mail your samples directly to the Lab. There have been instances in which the Lab never received clients’ samples mailed by stores.
10. How do I convert fertilizer or lime rates for larger lands to small areas, single rows or potted plants?
Fertilizer recommendations are usually given in pounds per acre and lime in tons per acre. For fertilizing small areas, single rows or potted plants, it is necessary to make conversion to suit your needs. You can click here to view conversion tables.
11. Why do I need to run a plant diagnostic analysis?
Plant analysis provides immediate diagnosis of nutrient deficiency, toxicity or imbalance. It serves as a supplemental tool to soil tests. It can monitor the effectiveness of your adopted fertilizer practices.
12. How do I take a plant sample?
Plant samples should be taken at early growth stages sensitive to nutrient requirements. Depending on crops, different parts of plant are taken for diagnostic analysis. General guidelines on what to sample are provided in Table 1 for field crops and Table 2 for vegetable crops. For crops you do not find in these tables, you may sample the youngest but fully mature leaves. Avoid soiled, diseased and insect-damaged or mechanically damaged plants and exclude dry and dead tissue. Please mail your plant samples in paper bags (no plastic bags) directly to the Lab.
13. What types of water samples can I send to the Lab for analysis?
We run water samples for agricultural and aquacultural applications.
14. What is your mailing address to send samples?
Since we are located on the LSU campus, we do not have a street address. Our mailing address is: LSU Soil Lab – SPESS, 122 M.B. Sturgis Hall, Baton Rouge, LA 70803
