Soil pH Calculator

Interactive pH slider (3–10) with colour-coded indicator and category (Extremely Acidic to Strongly Alkaline). Shows nutrient availability (N, P, K, Fe, Zn, Ca) at the current pH. Calculates lime (CaCO₃) dose to raise acidic soil or elemental sulphur dose to lower alkaline soil — per hectare, per acre and total — with approximate cost and application steps. Adjusts buffer factor for sandy, loamy or clay soils.

Soil pH Categories

Extremely Acidic: <4.5 — severe nutrient toxicity. Very Strongly Acidic: 4.5-5.0 — Aluminium toxicity. Strongly Acidic: 5.1-5.5 — Phosphorus fixation. Moderately Acidic: 5.6-6.0 — Optimal for some crops. Slightly Acidic: 6.1-6.5 — Ideal for most crops. Neutral: 6.6-7.3 — Maximum nutrient availability. Slightly Alkaline: 7.4-7.8 — Iron, Zinc deficiency. Moderately Alkaline: 7.9-8.4 — Micronutrient issues. Strongly Alkaline: 8.5-9.0 — Sodium problems. Very Strongly Alkaline: >9.0 — Severe constraints.

Nutrient Availability by pH

At pH 6.0-7.0: All nutrients maximally available. Below pH 5.5: Phosphorus fixed, Aluminium toxic. Above pH 8.0: Iron, Zinc, Manganese, Copper become unavailable. Calcium availability decreases below pH 5.5 and above pH 8.5.

Lime Requirement for Acidic Soil

Agricultural lime (CaCO₃) raises soil pH. Dose depends on current pH, target pH, and soil texture. Sandy soils need less lime, clay soils need more. Apply 2-4 months before planting for best results.

Sulphur Requirement for Alkaline Soil

Elemental sulphur (S) lowers soil pH. Soil bacteria oxidize sulphur to sulphuric acid. Apply 4-6 months before planting. Gypsum (calcium sulphate) can also help but doesn't change pH significantly.

Crop pH Preferences

Rice: 5.5-6.5, Wheat: 6.0-7.5, Maize: 5.8-7.0, Cotton: 6.0-7.5, Sugarcane: 6.0-7.5, Soybean: 6.0-7.0, Groundnut: 5.5-7.0, Potato: 5.0-6.5, Onion: 6.0-7.0, Tomato: 5.5-7.0.