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Agricultural gypsum: when to apply and how much

Before buying gypsum, check in the soil analysis whether it is recommended. Then see the dose and the cost per hectare.

Pre-sizing and estimating tool: the results do not replace a design, calculation, or report signed by a qualified professional, nor verification against the applicable standards.

VerificationRevision 12/11/2026

Technical responsibility. This calculator is under verification. The reference values and examples are hypothetical, to illustrate the calculation, and are not technical references. The user is responsible for the data entered, the choice of parameters, and the use of the results, and must validate them with a qualified professional before any decision, purchase, application, or construction work.

Soil analysis (20 to 40 cm layer)

The values come from the soil analysis of the 20 to 40 cm layer. Leave the price at 0 if you don't know it: the cost will not be calculated.

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—Recommended gypsum and dose
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Calcium at depth

Exchangeable calcium in the 20 to 40 cm layer, compared with the 0.5 cmolc/dm³ limit.

Tap the chart to see the values.

Aluminum saturation

Aluminum saturation compared with the 20% limit.

Tap the chart to see the values.

What if the data changes?

Drag the controls to simulate data different from what you entered (from 30% less to 30% more) and watch the result change instantly.

Tap the chart to see the values.

Gypsum dose and cost by clay content

Reference dose, total gypsum over the area, and cost for clay contents of 10% to 60%, with the area and price entered.

Step by step with your numbers

The calculation done in steps, with the values you entered.

    The calculation memo gathers this page's inputs, results, equations, assumptions, and references, with fields for project, responsible person, and review. The full report also includes the charts and interpretations, in color. In the print window, choose Save as PDF.

    How to use

    Use the soil analysis results for the 20 to 40 cm layer: exchangeable calcium and aluminum saturation. Enter the clay content and the gypsum price. The calculator says whether gypsum is recommended and, if so, the reference rate and cost.

    Worked example

    Clay of 30%, calcium at 20–40 cm of 0.3 cmolc/dm³ and aluminium saturation of 12%.

    Calcium below 0.5: gypsum recommended. Reference dose = 50 × 30 = 1,500 kg/ha.

    Precautions

    • Do not use this result as a prescription. The final decision belongs to the agronomist with the full analysis.
    • The criterion and dose are references that should be checked against current publications for your region.
    • See also the soil analysis: V% and m% for the rest of the correction.

    Method, assumptions, and references

    Equations used

    Recommendation: apply if the calcium in the 20 to 40 cm layer is below 0.5 cmolc/dm³, or if aluminum saturation is above 20%
    Gypsum dose (kg/ha) = 50 × clay content (%), as a reference; confirm in the fertilizer recommendation manual for your region
    Cost (R$/ha) = Dose (t/ha) × Price (R$/t)

    Assumptions and limits

    • The recommendation criteria are those of the reference technical note; review them against the current Embrapa publication and your region before deciding.
    • The reference dose is a practical rule based on clay content; the final recommendation is up to the agronomist.
    • The gypsum price is editable; there is no built-in market value.

    Standards and technical documents

    • Martinhão, D. (Embrapa Cerrados). Technical note on criteria for applying agricultural gypsum (2010). Review with current Embrapa publications.

    Frequently asked questions

    Does gypsum correct soil acidity?

    No. Gypsum works at depth, supplying calcium and reducing toxic aluminum in the subsoil. Surface acidity is corrected with limestone.

    Can I apply gypsum without an analysis?

    Not recommended. Applying without criteria creates cost with no response. Deep soil analysis is what shows whether there is a need.

    Why does the dose depend on clay?

    Because clayey soils hold more calcium and need more gypsum to reach the same condition. The rule of 50 kg/ha per % of clay is a starting reference.

    How long does the effect last?

    It depends on the soil, the rain, and leaching. That is why the analysis should be repeated after a few years to see whether reapplication is needed.

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