A soil test gives you numbers. This tool tells you what to do with them. Enter your pH, phosphorus band, and potassium band — the three values on almost every home soil test — and get specific amendment recommendations with rates and timing. The lime choice (calcitic vs dolomitic) depends on your magnesium level; the acidification method (elemental sulfur vs iron sulfate) depends on how fast you need results.
One warning most gardeners miss: if your phosphorus is already Excessive, adding bone meal, 10-10-10, or any fertilizer with a middle number above 0 makes your soil worse, not better. Excess phosphorus blocks iron and zinc uptake and contributes to runoff. This tool flags that situation explicitly. All recommendations are cited from university extension publications (Purdue, Penn State, Colorado State, UMN).
Frequently Asked Questions
What is the difference between calcitic and dolomitic lime?
Calcitic lime (calcium carbonate) raises pH and supplies calcium. Dolomitic lime raises pH and supplies both calcium and magnesium. Use dolomitic if your soil test shows low magnesium; use calcitic if magnesium is adequate or unknown. Applying dolomitic lime when magnesium is already adequate can create a calcium-magnesium imbalance.
How long does elemental sulfur take to lower soil pH?
Elemental sulfur works slowly — soil bacteria must convert it to sulfuric acid, which takes 4–8 weeks under warm, moist conditions. Apply at least 4–8 weeks before planting. For faster results, iron sulfate (ferrous sulfate) acts in 1–3 weeks but has a shorter-lasting effect.
My soil test says phosphorus is Excessive. What should I do?
Stop adding any fertilizer with a middle number above 0 — that includes bone meal, 10-10-10, garden tone, and most general-purpose fertilizers. Excessive phosphorus does not help plants grow and blocks iron and zinc uptake. Grow phosphorus-hungry crops like corn and brassicas to draw P down over 2–3 seasons, then retest.
What is the optimal pH range for vegetable gardens?
Most vegetables grow best between pH 6.5 and 7.0. This range keeps phosphorus, calcium, magnesium, and micronutrients (iron, manganese, zinc) all available. Below 6.0, aluminum and manganese can reach toxic levels. Above 7.5, iron, manganese, and zinc become unavailable even when present in the soil.
How do I read a soil test report?
Most lab reports show pH as a number (e.g. 6.2), and nutrients as a level (Low, Medium/Optimal, High/Excessive) or as ppm with an interpretation. Phosphorus and potassium are the most actionable numbers for home gardens. Magnesium is important for choosing lime type. If your report shows ppm without bands, ask the lab for the interpretation key or compare to extension thresholds for your region.