Team Organic Mandya ·
Water Quality Testing for Farm Irrigation: What to Test and Why
Most Indian farm borewells have never had their water tested — and poor-quality irrigation water silently degrades soil structure, accumulates toxic salts, and reduces yields over years before the cause is identified. Key parameters that matter for irrigation: EC (electrical conductivity, indicating total dissolved salts), SAR (sodium adsorption ratio, indicating whether sodium will damage soil structure), pH, and for organic farms specifically, the presence of heavy metals or industrial contamination if near industrial zones. A full water quality test costs ₹500–1,500 at a KSPCB or NABL-accredited lab. Every new borewell should be tested before use; existing borewells should be tested every 3–5 years.
EC <1.0 dS/m
Acceptable electrical conductivity for vegetable irrigation — higher values stress salt-sensitive crops
pH 6.5–8.0
Acceptable irrigation water pH — outside this range affects nutrient availability in soil
SAR <10
Sodium adsorption ratio below which sodium does not damage soil structure
₹500–1,500
Cost of a comprehensive farm irrigation water test at an accredited lab
What Are the Key Parameters to Test in Irrigation Water?
| Parameter | What It Measures | Acceptable Range for Vegetables | Problem If Out of Range |
|---|---|---|---|
| EC (Electrical Conductivity) | Total dissolved salts in the water | <1.0 dS/m (ideal); 1.0–2.0 dS/m use with caution; >2.0 dS/m avoid for vegetables | Salt stress on crops; progressive soil salinisation with repeated irrigation |
| pH | Acidity/alkalinity of water | 6.5–8.0 | Alkaline water (pH >8) leaves calcium deposits in drip emitters; acidic water is less common in India |
| SAR (Sodium Adsorption Ratio) | Sodium relative to calcium and magnesium | <10 (safe); 10–18 (marginal); >18 (damaging) | High sodium destroys soil aggregate structure — soil becomes compacted, impermeable clay |
| Chloride | Chloride ion concentration | <350 mg/litre | Above this level damages salt-sensitive crops (onion, strawberry, citrus) |
| Nitrate | Nitrogen as nitrate | <50 mg/litre (WHO standard for human consumption — use same for irrigation water safety) | High nitrate in water suggests upstream agricultural runoff or sewage contamination |
| Total Hardness (as CaCO₃) | Calcium and magnesium content | <300 mg/litre for drip systems | Hard water scales drip emitters; requires more frequent acid flushing |
| Iron | Dissolved iron | <0.3 mg/litre | Iron precipitates and blocks drip emitters; creates red-brown staining in pipes |
| Heavy metals (lead, chromium, cadmium) | Industrial contamination indicator | Should be non-detectable or within BIS/WHO safe limits | Accumulate in soil and crops; a certification risk for organic certification |
When Should You Test Your Farm Water?
| Situation | Test Required | Urgency |
|---|---|---|
| New borewell commissioned | Full test: EC, pH, SAR, chloride, hardness, iron, nitrate, heavy metals | Before first irrigation — do not irrigate without testing |
| Buying or leasing new farmland | Full test of all existing water sources | Before finalising the transaction — water quality affects land value and crop viability |
| Water colour or smell has changed | EC, pH, iron, sulphur compounds; possibly microbial | Immediate — stop irrigation until cause is known |
| Drip emitters blocking more frequently | Iron, hardness, EC | Within the current season |
| Applying for organic certification | Full panel including heavy metals | As part of certification documentation |
| Crop salt stress symptoms (leaf margin burn, stunted growth) | EC, SAR, chloride | Within days of symptoms appearing |
| Routine monitoring | EC and pH only (field test with basic meter) | Every 6–12 months for peace of mind |
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Visit Our Shop →How Do You Collect a Water Sample for Lab Testing?
Correct sampling procedure:
- Run the pump for 5 minutes before collecting the sample — stagnant water in pipes is not representative
- Use a clean plastic bottle (500 ml to 1 litre) — rinse with the same water 3 times before filling
- Fill bottle completely; leave no air space (minimises atmospheric contamination of the sample)
- Label clearly: source (borewell/pond), date, time, depth (for borewell)
- Deliver to the lab within 24 hours; if delayed, refrigerate but do not freeze
Where to get water tested in Karnataka:
- Karnataka State Pollution Control Board (KSPCB) district offices
- University of Agricultural Sciences (UAS) Bangalore/Mandya campus labs
- NABL-accredited private labs in major cities (search “NABL water testing lab Mysuru/Bangalore”)
- IARI-affiliated Krishi Vigyan Kendras (KVK) in most districts
Typical cost breakdown:
- Basic EC + pH (field meter): free with ₹1,500–3,000 meter purchase
- Standard irrigation water panel (EC, pH, SAR, major ions): ₹500–800
- Full panel including heavy metals: ₹1,200–2,000
What Do You Do If Water Quality Is Poor?
| Problem | Corrective Option | Cost |
|---|---|---|
| High EC (salty water) | Switch to drip irrigation to apply less volume; supplement with rainwater dilution; gypsum application to soil | Drip system ₹40,000–80,000/acre; gypsum ₹2,000–5,000/acre/year |
| High SAR (high sodium) | Gypsum (calcium sulphate) applied to soil competes with sodium; leach soil periodically with good water if available | ₹3,000–8,000/acre/year gypsum |
| High iron (emitter blocking) | Sand + screen filter; add iron removal filter (aeration tank and settling); annual acid flush of drip system | ₹5,000–15,000 for iron removal setup |
| High hardness (emitter scaling) | Annual or semi-annual acid flush (1% phosphoric or citric acid); use descaling additives in drip system | ₹500–1,000/acre/year for acid treatment |
| Microbial contamination (pond/open well) | Chlorination of water before irrigation (not recommended for organic farms); use for non-edible irrigation only | Use borewell for edible crops; treat before organic certification |
| Heavy metal contamination | Do not use for irrigation of food crops; investigate source; switch to alternative water source | Source investigation; alternative well siting |
Buy a Basic EC/pH Pen — It Pays for Itself in One Season
A basic combination EC and pH pen (₹1,500–3,000) lets you test your irrigation water monthly in 2 minutes. EC trending upward over months indicates increasing salt load — an early warning that lets you act before crops are visibly stressed. The same pen tests nutrient solution strength if you make liquid bio-inputs, verifies that your Jeevamrutha is properly diluted, and checks soil saturation paste EC for salt stress diagnosis. One tool, multiple uses, permanent value. Every farm with a drip system and a borewell should own one.
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