STK Soil Analyzer — Soil Test Kit Analyzer

How it works

Lab precision.
Zero lab required.

Your phone becomes a calibrated color reader. No internet. No equipment. Just your STK and a camera.

Prepare your sample

Collect a soil sample and prepare your STK reagents. The app walks you through each protocol step — CPR for Step 1 pH, then BCG or BTB for Step 2 — following laboratory-standard colorimetric procedures.

Two-step pH test

Capture the CPR indicator. The app auto-decides the next indicator: BCG (acidic soils, pH ≤ 5.4) or BTB (alkaline soils, pH ≥ 5.8). A built-in RETEST guard flags inconclusive readings (5.4–5.8 range).

Capture NPK readings

Photograph each NPK reagent: Diphenylamine (N), Barton's Reagent (P), and Sodium Tetraphenylboron (K). One capture per nutrient. CIEDE2000 matches the color to a calibrated ppm value.

Results & AI recommendations

Review your fertility score, NPK status, and pH classification with color swatches. Copy the structured AI prompt to clipboard and paste into Claude or ChatGPT for fertilizer and crop guidance.

Features

Objective readings.
Structured output.

Designed for agriculture students, farm technicians, and researchers who need accurate chemical data — not guesswork.

🧪

Two-Step pH Protocol

Follows laboratory-standard colorimetric procedures. Step 1 uses CPR indicator; the app auto-routes Step 2 to BCG (pH ≤ 5.4, acidic) or BTB (pH ≥ 5.8, alkaline). A built-in RETEST guard flags inconclusive readings in the 5.4–5.8 transition range.

🎨

CIEDE2000 Color Matching

Industry-standard perceptual color difference algorithm. Applied to both pH indicator colors (CPR / BCG / BTB) and NPK reagents (Diphenylamine, Barton's, Sodium Tetraphenylboron) for objective, lighting-tolerant readings.

📷

Camera Focus & Gallery Picker

A circular guide overlays the viewfinder so you can align the color strip precisely before capturing. If the camera fails to open, the gallery picker launches automatically — no test session is lost.

💬

Structured Prompt Generator

Converts your soil data into a clean technical summary. Copy to clipboard and paste into Claude, ChatGPT, or Gemini for fertilizer recommendations, crop suitability, and pH amendment guidance.

### SOIL ANALYSIS REPORT (STK)
Target Crop: PATOLA
Field Area: 1 hectare
------------------------------------------
### TEST STRIP RESULTS
- Soil pH: 4.2 (Extremely Acidic)
- Nitrogen (N): MEDIUM
- Phosphorus (P): LOW
- Potassium (K): HIGH
------------------------------------------
### ANALYSIS REQUEST
1. Recommended fertilizer types and NPK ratios.
2. Total nutrients required for the specified area.
3. Optimized application schedule (basal + top-dress).
4. Soil amendment advice if pH is outside ideal range.

📊

Results with Color Swatches

Full macro-nutrient profile — pH, Nitrogen (ppm), Phosphorus (ppm), and Potassium (ppm) — each shown alongside the extracted indicator color swatch for full traceability of every reading.

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Fertilizer Calculator

Select a crop and farm area. The calculator recommends Urea (46-0-0), TSP (0-46-0), MOP (0-0-60), and Dolomitic Lime based on your NPK status — with per-hectare amounts for basal and top-dressing.

🎛️

Custom Color Calibration

Every STK brand prints slightly different color strips. Calibrate the pH and NPK reference charts to match your exact kit. Settings are saved locally — no two farms need the same setup.

🌾

Sample Management

Record farmer name, address, farm location, and test dates per sample. Analyzed samples can be Reset & Retested (costs 1 credit) to prevent credit bypass. Export soil reports as gallery images anytime.

Legal

Terms & Conditions

Last updated: 2026

1. Purpose

STK Soil Analyzer is designed as a field guidance tool for estimating soil pH and NPK nutrient levels using colorimetric test kits. Results are approximations and should not replace certified laboratory soil testing for critical agricultural decisions.

2. Accuracy

Color-based readings depend on consistent lighting, test kit quality, and proper technique. The developer does not guarantee accuracy of results.

3. Limitation of Liability

The developer (Harold Rita) is not liable for any agricultural losses, decisions, or damages arising from the use or misuse of this application.

4. Data Ownership

All data you create in this app is stored locally on your device and belongs to you. The developer has no access to your data.

5. Changes

These terms may be updated with new app versions. Continued use constitutes acceptance of updated terms.

Legal

Last updated: 2026 · Your privacy is important to us.

Data Collection

STK Soil Analyzer does not collect, transmit, or share any personal information. All sample data, test results, and settings are stored exclusively on your device.

No Internet Required

The core app functions fully offline. An internet connection is only used if you choose to request AI crop recommendations via the structured prompt generator (optional feature).

Camera

Camera access is used solely to capture photos for color analysis. Photos are processed on-device and are not uploaded or stored beyond the immediate analysis session.

Third-Party Services

Optional AI recommendations are generated via external AI models (e.g. Claude, ChatGPT). No data is stored by these services beyond your session. Usage of these services is entirely at your discretion.

Contact

For privacy concerns, contact the developer at github.com/phpthinky.

Google Play Store Listing

Store Copy

Ready-to-paste copy for Google Play Console. Character counts shown for each field.

App Title (max 50 chars)

29 / 50

STK Soil Analyzer – pH & NPK

Short Description (max 80 chars)

77 / 80

Measure soil pH & NPK offline using colorimetric test kits. AI-ready reports.

Long Description (max 4,000 chars)

≈ 2,400 / 4,000

STK Soil Analyzer is a mobile field tool for agricultural technicians, students, and farmers who need objective soil chemical data — without laboratory equipment.

Use any standard Soil Test Kit (STK). The app guides you through a laboratory-standard colorimetric protocol and analyzes each result using the CIEDE2000 color science algorithm — the same standard used in professional color industries — for readings more consistent than the human eye.

━━━ TWO-STEP pH TEST (LABORATORY STANDARD) ━━━

Step 1: Capture your CPR (Color pH Reagent) indicator color.
The app automatically evaluates the result:

  • pH ≤ 5.4 → proceed with BCG indicator (acidic soils)
  • pH ≥ 5.8 → proceed with BTB indicator (alkaline soils)
  • pH 5.4–5.8 → Inconclusive — reset and retest with a fresh sample

Step 2: Capture the BCG or BTB indicator.
Final pH is computed and saved to the sample record.

━━━ NPK NUTRIENT ANALYSIS ━━━

• Nitrogen (N) — Diphenylamine reagent
• Phosphorus (P) — Barton's Reagent
• Potassium (K) — Sodium Tetraphenylboron reagent

Each nutrient is classified as LOW / MEDIUM / HIGH. The extracted indicator color is shown as a swatch alongside each reading for full traceability.

━━━ AI-READY TECHNICAL SUMMARY ━━━

Once all parameters are captured, the app generates a structured soil report prompt. Copy it to clipboard and paste into Claude, ChatGPT, or Gemini to receive fertilizer recommendations, crop suitability analysis, and pH amendment guidance — no integration required.

━━━ KEY FEATURES ━━━

✓ Two-step pH protocol following laboratory standards
✓ CIEDE2000 color science for objective, consistent readings
✓ NPK classification: LOW / MEDIUM / HIGH per nutrient
✓ Fertility score and recommended crop matching
✓ Built-in fertilizer calculator (Urea, TSP, MOP, Dolomitic Lime)
✓ Camera focus circle guide for precise strip alignment
✓ Gallery picker fallback if camera fails to open
✓ Color swatch preview alongside every test result
✓ Soil Analysis Report — save to device gallery as image
✓ 100% offline — no internet required for testing
✓ All data stored locally on your device — zero server access
✓ No ads, no analytics, no account required

━━━ CREDIT SYSTEM ━━━

Every install includes 10 free analysis credits.
• Creating a new sample costs 1 credit
• Retesting an already-analyzed sample costs 1 credit
• Top up anytime with token-based credits — no subscription, no expiry

━━━ CUSTOM CALIBRATION ━━━

Every STK brand prints slightly different color strips. Adjust the pH and NPK reference color charts to match your specific kit — saved locally on your device.

━━━ PRIVACY ━━━

STK Soil Analyzer does not collect, transmit, or share any personal data. Camera is used only for on-device color extraction. No analytics. No ads.

Developed by Harold V. Rita · github.com/phpthinky
Part of the TAMAD (Tech-Agri for Mindoro Agile Development) ecosystem · Sablayan, Occidental Mindoro 🇵🇭

Read your soil.
Know what to grow.

1. Purpose

2. Accuracy

3. Limitation of Liability

4. Data Ownership

5. Changes

Data Collection

No Internet Required

Camera

Third-Party Services

Contact

App Title (max 50 chars)

Short Description (max 80 chars)

Long Description (max 4,000 chars)

Precision readings.
Ready for any AI.

Read your soil.Know what to grow.

1. Purpose

2. Accuracy

3. Limitation of Liability

4. Data Ownership

5. Changes

Data Collection

No Internet Required

Camera

Third-Party Services

Contact

App Title (max 50 chars)

Short Description (max 80 chars)

Long Description (max 4,000 chars)

Precision readings.Ready for any AI.

Read your soil.
Know what to grow.

Precision readings.
Ready for any AI.