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Enter your soil test targets to size compost, lime, and sulfur needs for this bed.
Soil amendment planning usually starts with two separate gaps. One gap is chemistry: the soil may be too acidic for a vegetable bed, or not acidic enough for blueberries and other acid-loving plants. The other gap is organic matter: the bed may drain too fast, crust after irrigation, or stay hard to work because it needs more compost and more biological residue in the topsoil.
This calculator turns those gaps into material quantities you can actually buy and move. Enter the bed area, incorporation depth, soil texture, current and target pH, current and target organic matter, and a goal preset such as Vegetable bed reset, Leafy greens and herbs, Blueberries and acid lovers, Clay bed rehab, or Perennial border. The result can include finished compost, agricultural lime, elemental sulfur, optional gypsum, bag counts, wheelbarrow loads, total carried weight, and a material budget.
It is most useful for raised beds, kitchen gardens, borders, and other small plots where bag sizes and hauling matter almost as much as the soil numbers. The Field Sheet tab shows the core recommendation and the Buy list. Staging Plan turns the same run into an application sequence and follow-up checklist. Material Loadout charts the weights by material, and JSON preserves the run as a structured record you can copy or download.
The result is a planning estimate, not a promise of the exact soil test you will see later. The calculator uses shipped texture factors or an optional lab lime factor, then adjusts for lime quality, sulfur assay, and the focus mode you selected. That is useful for work planning, but it does not replace a current soil test, product label checks, or a retest after the amendments have had time to react.
The calculation begins with bed geometry. Bed area is converted to square feet, Target depth is converted to inches, and those two values produce the working soil volume. From there the run splits into two paths. The pH path decides whether lime or sulfur is needed. The organic matter path decides whether compost is needed. Those quantities stay separate until the end, when the page combines them into a loadout, package counts, and cost summary.
The shipped Soil goal profile presets fill in target pH and target organic matter together, which makes the tool useful for common garden jobs without forcing you to start from a blank form. The preset only supplies targets. The actual recommendation still depends on the current soil values you enter, the soil texture, the pH sizing method, and product-strength fields such as Lime CCE and Sulfur assay.
| Soil texture | Lime factor | Sulfur factor | Gypsum factor |
|---|---|---|---|
| Sandy loam | 3.5 | 0.9 | 2.0 |
| Loam | 4.5 | 1.2 | 2.8 |
| Clay loam | 6.0 | 1.5 | 3.6 |
| Heavy clay | 7.5 | 1.8 | 4.5 |
The lab-based pH path is narrower than the texture path. If pH sizing basis is set to Soil test lime factor and you are raising pH, the tool uses the entered lime factor in pounds of calcium carbonate per 1,000 square feet for each 0.1 pH step. If you are lowering pH, sulfur still follows the texture table. Lime demand is then adjusted by Lime CCE, and sulfur demand is adjusted by Sulfur assay, so weaker products require more weight.
The focus selector only nudges the mineral recommendation; it does not rewrite the whole run. Organic matter first reduces lime and sulfur by 15 percent when compost is also being added. Raise pH priority increases lime by 10 percent when lime is needed. Lower pH priority increases sulfur by 10 percent when sulfur is needed. Gypsum is independent of the pH path. When Include gypsum is enabled, the page adds a texture-based gypsum quantity but does not change the pH target or the pH correction math.
| Control or field | What it changes | What it does not change |
|---|---|---|
| Bed area, Target depth, Soil texture, pH values, OM values | Base compost, lime, sulfur, gypsum, soil volume, and soil mass | Packaging assumptions already entered in Advanced |
| Soil goal profile, Amendment focus, pH sizing basis, Lab lime factor | How target bands are loaded and how mineral correction is sized | Wheelbarrow loads, bag counts, and cost until material amounts exist |
| Lime CCE, Sulfur assay, Include gypsum | Material weights for lime, sulfur, and optional gypsum | Compost volume from the organic matter gap |
| Bulk density | Displayed Soil mass | Compost, lime, sulfur, gypsum, and cost |
| Wheelbarrow capacity, Compost density, bag sizes, bag costs | Loads, package counts, carryover, and budget | The core amendment quantities |
The page also enforces practical input limits. Area and depth must be positive, depth is held between 2 and 12 inches, current pH between 4.0 and 8.5, target pH between 5.0 and 7.5, current organic matter between 0.5 and 12 percent, target organic matter between 1 and 15 percent, lime CCE between 60 and 110 percent, and sulfur assay between 70 and 99 percent. If a required condition is not met, the red alert explains the problem and the result tabs stay hidden.
Start with a recent soil test whenever you can. Pick the closest Soil goal profile, leave Amendment focus on Balanced (soil test), and keep pH sizing basis on Texture estimate unless your soil lab gave you a lime requirement factor. That first pass shows whether the job is mainly about raising pH, lowering pH, building organic matter, or simply translating a moderate recommendation into bag and hauling terms.
Do not confuse buying math with soil chemistry. Compost density, Wheelbarrow capacity, and bag sizes can make Total amendment weight look large even when the pH material is modest. That is normal. A bed can need only a few pounds of lime or sulfur but still require hundreds of pounds of compost once volume is converted into a delivered weight.
The most important lines are usually Compost required, Lime required or Sulfur required, Gypsum, and Retest window. Those tell you what the bed actually needs. The chart, bag counts, and total weight help with execution, but they do not change the recommendation itself.
| Output cue | What it means here |
|---|---|
| Compost required dominates the run | The main job is building organic matter and structure. The pH correction may be minor even if the total carrying weight is high. |
| Lime required or Sulfur required changes sharply after editing Lime CCE or Sulfur assay | The product-strength correction is doing its job. Lower-quality material means more pounds are needed. |
| Sulfur pass plan switches to two passes | The sulfur rate reached the tool's 4 lb per 100 sq ft staging threshold, so the page asks for a split application and a retest before pass two. |
| Total material cost is shown as — | The amendment math is still valid. The page is only missing bag prices. |
The main false-confidence trap is treating the displayed pH path as a guaranteed future soil test. It is not. It is the correction target you asked the tool to size. Before you trust a large amendment round, verify the current soil test, confirm the actual CCE or sulfur percentage on the bag, and retest after the recommended waiting period. That is especially important for blueberries and other acid-loving beds, where sulfur timing and soil response matter as much as the weight calculation.
A 200 sq ft bed worked to 6 inches with Loam, Vegetable bed reset, current pH 5.8, target pH 6.5, current OM 3.2%, target OM 5.5%, Balanced (soil test), and 90% Lime CCE produces a practical garden-scale plan. The Field Sheet shows about 0.35 cu yd of compost, about 7.0 lb of agricultural lime, one 40 lb lime bag, about four 3 cu ft wheelbarrow loads of compost, and a Retest window of next season.
The important reading is not the lime bag count. It is that the bed needs both organic matter and a moderate pH increase, and the hauling burden comes mostly from compost. In the Buy list, the compost line drives the lift and the lime line is a small follow-on correction.
Try a 120 sq ft bed at 6 inches with Sandy loam, the Blueberries and acid lovers preset, current pH 6.4, current OM 4.0%, target pH 5.0, target OM 7.0%, and the default 90% sulfur product. The run produces roughly 0.27 cu yd of compost and about 1.7 lb of sulfur, with the sulfur still in a single pass because the Sulfur rate stays below the split threshold.
That output matches the kind of job blueberry beds usually need: more organic matter, lower pH, and patience. The small sulfur weight does not mean the change is immediate. The useful signal is the combination of sulfur plus an early-start timeline, followed by a retest months later rather than a quick spot check.
Suppose a 300 sq ft clay loam bed needs to move from pH 5.4 to 6.7 and you switch pH sizing basis to Soil test lime factor because the lab report gave a liming recommendation. If Lab lime factor is left at 0, the red alert appears and the result tabs do not show. That is the correct failure path, because the lab method has no value to work from.
Once you enter a real factor such as 8.0 lb per 1,000 sq ft per 0.1 pH, the run becomes valid again and the pH sizing basis line in Field Sheet changes to the lab-driven method. At 90% CCE, that case lands near 34.7 lb of lime, which is enough to change the bag count and the staging notes in a way a generic texture estimate would not.
No. The calculator is best used with a recent soil test, not instead of one. The Texture estimate path is useful when you only have pH and organic matter values, but the more exact raising-pH path is the Soil test lime factor option when your lab provides that number.
That happens when the calculated Sulfur rate reaches 4 lb per 100 sq ft or more. In that case the tool changes Sulfur pass plan to a split application about 6 months apart and asks for a retest before the second pass.
Because the tool treats gypsum as an optional calcium and structure material, not as the pH-correction agent. That matches extension guidance: gypsum supplies calcium and sulfur but does not act as a liming or acidifying material. In many gardens it is not a universal cure for heavy clay on its own.
The big number often comes from compost. Total amendment weight includes compost after the chosen Compost density converts volume into pounds or kilograms. A modest lime correction can ride alongside a much heavier compost delivery.
The most common causes are simple: Bed area or Target depth is zero or negative, or Lab lime factor is missing while Soil test lime factor is selected for a lime run. The page keeps Field Sheet, Staging Plan, Material Loadout, and JSON hidden until those inputs are valid.
The calculator has no server-side processing path for the amendment run itself. It calculates in the page and then lets you copy or download CSV, DOCX, chart images, and JSON from that local result state.