About SoilTune
SoilTune is a suite of 10 free soil science calculators covering the measurements that drive amendment decisions: lime requirement, pH adjustment, CEC, base saturation, gypsum, irrigation water quality and fertigation.
It exists because the useful version of these calculations usually lives in a consultant's spreadsheet, a extension bulletin table, or buried in software you have to pay for before you can see the working. We think the opposite should be true: you should be able to see every step, change every assumption, and check the result against your own numbers.
SoilTune is published by Azmi Mhamed, publisher and author, the person responsible for this site, its formulas and its editorial choices.
Show the derivation
A number you can't check is a number you can't trust. Every calculator prints the formula it used, the constants it applied and the intermediate steps, so the result can be reconciled against a lab report or a spreadsheet.
Reference, don't prescribe
Targets and conversion factors come from published agronomic practice: USDA-NRCS models, standard equivalent weights, SMP and buffer methods. Where programs disagree, we show the range rather than pick a side.
Keep data local
Nothing you enter is sent anywhere. The calculations run in your browser, which means soil test data stays on your machine and there is no account, no tracking of inputs and no export queue.
What we cover
Soil chemistry: lime, pH down, CEC, base saturation, gypsum and SAR: handles the reservoir: how much charge the soil holds, how it is divided between cations, and how quickly it will respond to an amendment. Fertigation (blend formulation and PPM → EC) handles what goes into the tank and onto the field.
Both hubs are the fastest way in: soil chemistry calculators and fertigation calculators.
Limitations
These tools produce planning estimates from the values you enter. They do not replace a soil test, a plant tissue analysis, or a certified agronomist who has walked the field. Buffering behaviour varies with mineralogy, organic matter and history; product purity varies by manufacturer and batch; and label rates are legally binding in a way our estimates are not. Confirm rates against your lab, your product label and local regulation before buying or applying anything.
How we check our numbers
Every figure on this site has to be traceable to something a reader can check. A number either falls out of a calculator, where the formula, the constants and the intermediate steps are printed with the result, or it is quoted in a guide with a link to the bulletin, standard or laboratory method it came from. Nothing is published on the strength of an assertion alone.
The full library was re-checked on 28 September 2026. Thirty-three source links across eleven guides (29 unique addresses) were re-requested from the live site: every one answered HTTP 200, and each linked sentence was read again against the source it cites. Figures that could not be traced to a source were rewritten against one or taken out: fourteen claims across ten guides.
Sources we cite
The citation set is deliberately boring: university extension services (Penn State, Clemson, NC State, Colorado State, Purdue, NDSU, Oregon State, Wisconsin, Delaware, Mississippi State and others), USDA-NRCS, US EPA, and the published methods of soil testing laboratories. Where those sources disagree (buffer methods and lime factors are the usual case), the range is shown rather than a single number picked out of it. A citation stays on the page only while its address answers and its text still says what we said it says.
The citations the calculators themselves print are collected in the calculator sources register: one table per tool, transcribed from the reference block that tool publishes, with a link wherever the source still answers.
Corrections log
- 28 September 2026: re-verified all 33 external source links (29 unique addresses, all HTTP 200) and re-read each cited sentence; rewrote or removed 14 figures that could not be traced to a source; added extension bulletin citations for the figures that had been uncited.
Anything corrected after this date is added to the same list with the date and what changed. If you spot a formula, constant or reference that looks wrong, tell us via the contact page: cite the calculator and the value in question and we will review it.
Editorial responsibility
SoilTune is published by Azmi Mhamed, who is responsible for its formulas, sources and editorial choices. Because a small site cannot lean on a masthead, the authority it offers is the working itself: derivations are printed, sources are linked at the sentence they support, and corrections are logged with a date above. That is the standard every guide and calculator on this site is held to.