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Water Quality for Irrigation: Testing and Treatment

Irrigation · January 2026 · 5 min read

Irrigation water quality directly affects crop health, soil structure, and equipment longevity, yet many farmers never test their water source. High salinity, sodium, bicarbonates, or extreme pH can reduce yields, degrade soil, and clog drip emitters over time. A basic water quality test costs under $100 and provides the information you need to manage or treat your water before it causes problems.

Key Water Quality Parameters

The most important irrigation water measurements are electrical conductivity (EC), sodium adsorption ratio (SAR), and pH. EC measures total dissolved salts; values above 1.5 dS/m begin to restrict sensitive crops while values above 3.0 dS/m affect most field crops. SAR indicates sodium hazard; values above 9 can destroy soil structure over time.

Bicarbonates above 120 ppm cause lime deposits on leaves and clog drip emitters. Chloride above 140 ppm causes leaf burn on sensitive crops like strawberries and stone fruits. Iron and manganese stain produce and plug micro-irrigation systems even at low concentrations.

pH Effects and Nutrient Availability

Water pH affects nutrient solubility and pesticide efficacy in your spray tank as well as soil chemistry over time. Irrigation water with pH above 7.5 reduces the effectiveness of many insecticides and herbicides. Water with pH below 6.0 can increase the solubility and potential toxicity of certain metals like aluminum and manganese.

• Acidification: Inject sulfuric or phosphoric acid to lower pH for drip systems and spray water
• Buffering: High-bicarbonate water resists pH change and requires more acid to adjust
• Lime buildup: Alkaline water gradually raises soil pH, potentially requiring sulfur applications to correct

Filtration and Treatment Options

All drip and micro-irrigation systems need filtration matched to the water source. Sand media filters handle organic matter and algae from surface water. Disk and screen filters work for well water with mineral sediment. Size the filter system to handle your peak flow rate without excessive pressure loss.

Chlorination controls biological growth in drip lines and storage tanks. Inject sodium hypochlorite or calcium hypochlorite at 1-2 ppm free chlorine for continuous treatment, or use higher rates for periodic line flushing. Acid injection addresses bicarbonate problems and prevents scale buildup in emitters and pipes.