Soil Testing Methods

You cannot manage what you don't measure. Soil testing is the starting point of all serious organic farming — and many tests can be done in minutes with no equipment.

Basic Field Tests (Farmer Level)

Jar/Settlement Test — Soil Texture

What you need: Glass jar with lid, water, pinch of salt

1. Fill jar 1/3 with soil
2. Fill with water, add pinch of salt (helps particles settle)
3. Shake vigorously for 1 minute
4. Let settle for 24 hours
5. Observe layers:
   • Bottom layer (settles first): Sand
   • Middle layer: Silt
   • Top layer (settles last): Clay
   • Floating organic matter: Humus (good sign — the more, the better)
6. Measure layers and estimate percentage of each

Interpretation:

• Mostly sand (bottom thick): Sandy soil — add compost + clay, improve water retention
• Mostly clay (top thick): Clay soil — add gypsum + compost for structure
• Roughly equal layers: Loam — excellent, maintain with compost

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Vinegar + Baking Soda Test — pH Quick Check

Accuracy: ±1 pH unit (useful directional indicator)

For alkaline soil:

• Add 2 tbsp vinegar (acid) to 2 tbsp dry soil
• Fizzing = alkaline (pH >7) — calcium carbonate reacting with acid

For acid soil:

• Add 2 tbsp baking soda dissolved in a little water to 2 tbsp dry soil
• Fizzing = acid (pH <7) — acid soil neutralizing base

No reaction to either = approximately neutral pH 6.5–7.0

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Squeeze Test — Soil Structure

1. Wet a handful of soil (not dripping)
2. Squeeze firmly
3. Release and observe:
   • Falls apart immediately: Too sandy — poor structure
   • Stays as sticky blob, doesn't crumble: Too clayey — compaction risk
   • Forms shape then gently crumbles when poked: Good loam structure ✓

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Earthworm Count — Biological Health

The fastest indicator of soil health.

1. Dig a cube 30cm × 30cm × 30cm
2. Count all earthworms (including small ones)
3. Return soil gently

Interpretation:

• 10 worms: Good biological health

• 5–10 worms: Moderate — needs organic inputs
• <5 worms: Poor — pesticide damage or low organic matter
• 0 worms: Severely degraded soil — emergency organic intervention needed

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Water Infiltration Test

1. Push a 30cm metal ring 15cm into soil
2. Fill with 15cm of water
3. Time how long it takes to fully drain

Interpretation:

• Drains in <30 minutes: Good structure (healthy organic soil)
• Drains in 30–60 min: Moderate compaction
• Drains in >60 min: Poor structure — tillage pan, compaction, or heavy clay

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Lab Tests — What to Order

For serious organic farming, get a lab test before starting and every 2–3 years to track progress.

Test	Purpose	Target Values	Cost (India)
pH	Acidity/alkalinity	6.0–7.0	₹50–100
EC (Electrical Conductivity)	Salinity	<0.5 dS/m	₹50
Organic Carbon (OC%)	Soil health indicator	>1.0%	₹100–200
Available Nitrogen	N status	>280 kg/ha	₹100
Available Phosphorus	P status	>22 kg/ha	₹100
Available Potassium	K status	>280 kg/ha	₹100
Micronutrients (Zn, Fe, Mn, Cu, B)	Deficiency diagnosis	Crop-specific	₹200–500

Priority order: pH first, then OC, then macro NPK, then micronutrients.

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Where to Get Soil Tested in India

Source	Cost	Turnaround	Notes
Soil Health Card Scheme (govt)	Free	2–4 weeks	Covers pH, EC, OC, NPK + micronutrients. Apply at your local agricultural office.
KVK (Krishi Vigyan Kendra)	Subsidized (₹50–200)	1–2 weeks	Most districts have one.
ICAR Regional Labs	₹200–500	1–2 weeks	More comprehensive analysis
State Agriculture Dept Labs	₹100–300	Varies	Quality varies by state
Private Labs	₹500–2,000	1 week	Fastest, most comprehensive

Tip: Under the Soil Health Card scheme, you're entitled to a free soil test every 2 years. Use it.

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How to Take a Soil Sample

1. Collect from 5–10 spots across the field (zigzag pattern)
2. Depth: 0–15cm for topsoil test (where crops feed)
3. Remove surface debris and grass
4. Mix all samples in clean bucket — take 500g from mix
5. Air dry in shade (never oven — this changes OC)
6. Label clearly: field name, date, crop history, irrigation source

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Next: How to Restore Damaged Soil