Horticulture tool
Clemson Soil Acidification Calculator
QR: new blank toolPublished values
Crop pH targets this calculator can fill in
The crop picker fills the target pH field from the 6 rows below. Your crop does not have to be one of them — if it is not listed, enter the target pH your soil test report or your crop’s own guidance gives you, which is what the field expects by default.
These values come from two Clemson publications that answer two different questions, and the table says which question each row answers. A plant optimum is the pH range a plant grows best in, published by the Home & Garden Information Center without reference to any soil test. A soil test target is the pH the Clemson Agricultural Service Laboratory publishes as the goal for a crop, and it is generally the higher of the two. So a soil test report may well name a higher pH for the same crop than this table does. The two numbers are not in conflict; they are answers to different questions, and it is the plant optimum that an acid-loving crop actually wants.
Where a source publishes a range rather than a single value, this calculator aims at the high end of it. Overshooting acidification is slow and expensive to reverse, and any rate above the per-application sulfur limit is already split across applications two to three months apart, so there is time to re-test and stop short.
| Crop | Published as | Published value | Fills in as | Source |
|---|---|---|---|---|
| Azaleas | Plant optimum | pH 5.0 to 5.5 | pH 5.5High end of the published optimum range | Clemson HGIC, 2026 |
| Blueberries | Plant optimum | pH 5.0 to 5.5 | pH 5.5High end of the published optimum range | Clemson HGIC, 2026 |
| Camellias | Soil test target | pH 6.0 | pH 6.0Published target | Clemson Agricultural Service Laboratory |
| Centipede grass | Soil test target | pH 6.0 | pH 6.0Published target | Clemson Agricultural Service Laboratory |
| Conifers, including pines and Christmas trees | Plant optimumPublished for conifers as a group, not for each species. | pH 5.0 to 5.5 | pH 5.5High end of the published optimum range | Clemson HGIC, 2026 |
| Rhododendrons | Plant optimum | pH 5.0 to 5.5 | pH 5.5High end of the published optimum range | Clemson HGIC, 2026 |
- Kluepfel, M., Lippert, B., & Williamson, J. (2026). Changing the pH of your soil (HGIC 1650). Clemson Cooperative Extension Home & Garden Information Center. https://hgic.clemson.edu/factsheet/changing-the-ph-of-your-soil/
- Soil pH management (section V) and acid soil pH adjustment by liming (section VI), in pH Management, Clemson Agricultural Service Laboratory fertility recommendations. Linked from the laboratory's soil testing page, clemson.edu/public/regulatory/ag-srvc-lab/soil-testing/ (accessed September 8, 2026).
About this tool
About the Clemson Soil Acidification Calculator
Calculate the proper amount of agricultural sulfur or aluminum sulfate to apply for lowering your soil pH, from your soil type, current soil pH, and the target pH your crop needs.
For most South Carolina soils and crops, lowering soil pH is not necessary. In some cases it is worth doing: blueberries, azaleas, camellias, rhododendron, centipede grass and other acid-loving plants grow better in soil more acidic than the general optimum. The Clemson Soil Acidification Calculator estimates how much elemental sulfur or aluminum sulfate it takes to move a soil from the pH your soil test reports to the pH your crop wants. It is published by Clemson Cooperative Extension and the Clemson University Center for Agricultural Technology.
What it calculates
Select your soil type, enter the soil pH from your soil test report, and set a target pH — type it in, or switch the target to Suggest from crop and choose a crop to fill in its published value. The calculator returns the amount of elemental sulfur required, and the equivalent amount of aluminum sulfate, reported per acre and per 1,000 square feet for home, garden, lawn and ornamental applications, or per hectare in metric. Enter a treatment area and it also reports the total amount of product to buy.
Reading the results
Most recommendations this calculator produces are larger than one application should deliver. The published limit is 218 to 436 pounds of sulfur per acre — 5 to 10 pounds per 1,000 square feet — per application, stated as a maximum in Southern Lawns (McCarty, ed., Clemson University, EC 707, 2003), and the calculator divides anything above 327 pounds per acre — the middle of that published band — into the number of applications required. Splitting further is always an option; a schedule two to three months apart is a real cost of its own, which is why the tool does not assume the lowest figure in the band. The same source sets the spacing: repeat applications no more often than once every two to three months, only when temperatures are cool (below 75°F), watered in immediately after application. Re-check soil pH between applications rather than assuming the remaining schedule still applies.
Elemental sulfur and aluminum sulfate are alternatives, not a combined application. Granular, superfine dust, or wettable sulfur may all be used; granular sulfur suits home lawns because it spreads with a cyclone fertilizer spreader and is less likely to burn foliage.
Limits
These rates are estimates for mineral soils in South Carolina and do not replace the recommendations printed on your soil test report. Take two or more soil samples from the area before acting on a pH reading. The calculator covers soil pH from 5.0 to 8.0 and target pH from 4.5 to 6.5.
References
- Clemson Agricultural Service Laboratory. (n.d.). Soil pH management. Clemson University Regulatory Services. Linked from the laboratory's soil testing page, clemson.edu/public/regulatory/ag-srvc-lab/soil-testing/ (accessed September 8, 2026).
- McCarty, L. B. (Ed.). (2003). Southern lawns: Best management practices for the selection, establishment, and maintenance of southern lawngrasses (EC 707). Clemson University Public Service Publishing. ISBN 978-0-9712527-6-9. Source of the per-application sulfur limit and the two-to-three-month repeat-application interval.
- Kluepfel, M., Lippert, B., & Williamson, J. (2026). Changing the pH of your soil (HGIC 1650). Clemson Cooperative Extension Home & Garden Information Center. https://hgic.clemson.edu/factsheet/changing-the-ph-of-your-soil/
- Sekaran, U., Alford, S., & Farmaha, B. S. (2022). Interpreting routine soil tests (LGP 1151). Clemson University Land-Grant Press. https://lgpress.clemson.edu/publication/interpreting-routine-soil-tests/
Authorship and attribution
Authors: K. Kirk, M. Plumblee, F. McAlhany
Organizations: Clemson Cooperative Extension; Clemson University Center for Agricultural Technology
Last updated: Sep 9, 2026
Suggested citation: K. Kirk, M. Plumblee, & F. McAlhany (2019). Clemson Soil Acidification Calculator [Interactive calculator]. CU-CAT Apps, Clemson University Center for Agricultural Technology. Retrieved September 9, 2026, from https://apps.cuagtech.com/soil-acidification
CU-CAT Apps is developed and hosted by Clemson University Center for Agricultural Technology, in partnership with Clemson Cooperative Extension Service.
CU-CAT Apps and its calculators, reports, and results are provided as-is for informational and educational purposes. Accuracy and completeness are not guaranteed. Users are responsible for evaluating the source information and outputs and assume the risks arising from their use.
