Water Testing in Agriculture: How to Interpret and Improve Water Quality

Water Analysis Interpretation for Agriculture

Water quality is one of the most overlooked yet critical factors in modern agriculture.
Whether you use water for irrigation, fertigation, or preparing nutrient solutions, its chemical composition directly affects nutrient availability, soil health, and crop performance.

Why Water Testing Matters in Agriculture

Water is far more than just H₂O - it’s a complex solution containing dissolved salts, bicarbonates, and nutrients that can either support or restrict plant growth.

When water quality is unbalanced, especially with high pH or bicarbonate (HCO₃⁻) levels, it can lead to:

• Nutrient precipitation, particularly of iron (Fe) and zinc (Zn)
• Clogging of drippers and emitters in irrigation systems
• Reduced nutrient uptake and increased plant stress

However, testing isn’t just about identifying issues - it’s also about optimizing your fertilizer program.
Knowing which macro- and micronutrients are already present in your water allows you to balance fertilizers more accurately, avoiding over-application, saving money, and keeping the nutrient ratio right for your crops.

Different Water Sources and Their Typical Characteristics

Even two wells drilled just a few meters apart can produce completely different water profiles.
That’s why it’s crucial to test your specific water source before each growing season and repeat the analysis at least once per year - ideally before the main vegetative growth phase, when plants begin to actively absorb nutrients and water demand increases.

Regular testing allows growers to fine-tune acidification, filtration, and fertilizer formulations - preventing costly problems before they appear in the field.

How Water Composition Affects Crop Performance

• High bicarbonates (HCO₃⁻) - gradually raise the pH in the root zone, reducing the solubility and availability of key nutrients such as iron (Fe), zinc (Zn), and manganese (Mn). Over time, this can lead to hidden deficiencies and yield loss.
• Excess sodium (Na⁺) - causes soil dispersion, poor structure, and reduced infiltration. As a result, roots receive less oxygen and water movement becomes inefficient.
• Unbalanced calcium-to-magnesium ratio (Ca/Mg) - disrupts nutrient uptake and can affect soil permeability. A high Mg level can compact soil, while too much Ca may cause micronutrient deficiencies.
• High EC (salinity) - limits water absorption by plants, causing osmotic stress and reduced growth.
• In short, poor water composition doesn’t just affect irrigation systems - it changes soil chemistry and plant nutrition balance, directly influencing yield potential.

Water by Application Purpose

Irrigation Water

• Target pH: 6.0–7.0
• If pH is high, use acidification or blending with water from a lower-pH source.
• Filtration is essential to prevent dripper and sprinkler clogging. Typical methods: sand filters, disc filters, or screen filters.

Fertigation Water

• Target pH: 5.5–6.5
• Acidification lowers pH and bicarbonates, but also reduces buffer capacity. Add acids gradually and monitor pH and EC regularly.
• Maintain filtration to protect emitters from clogging - usually sand, disc, or screen filters, sometimes combined with media filters for finer particles.

Nutrient Solution Preparation

• Use RO (reverse osmosis) water when possible (EC < 0.1 mS/cm) for maximum precision.
• RO water has very low HCO₃⁻, which can make pH unstable - buffer appropriately (e.g., with KHCO₃) before adding fertilizers.
• Ensure water contains minimal impurities for accurate nutrient formulation.
• Additional fine filtration can include ultra-filters or micron filters to remove particles and microorganisms.

Practical Tips

• Use acids carefully - they lower both pH and bicarbonates. Always add acid to the water, never the other way around, and do it gradually in small portions to better control the pH drop.
• Avoid unstable pH - water with low buffering capacity can stress plants, while high bicarbonate levels may clog emitters and damage irrigation and fertigation systems. Maintaining stable pH and balanced water chemistry helps protect both crops and equipment.
• When adjusting water or nutrient solutions, apply acids, buffers (e.g., KHCO₃), and fertilizers in portions, step by step. This makes it easier to:
  • monitor pH changes when adding acids,
  • control buffer capacity when using KHCO₃,
  • ensure proper mixing of regular fertilizers.
    During application, regularly monitor pH and EC to avoid spoiling the final nutrient solution or concentrate.
• If water has pH above 6.1, consider using chelated micronutrients to maintain nutrient availability and prevent deficiencies.

Conclusion

Water testing isn’t just a lab formality - it’s the foundation of precision agriculture.
Understanding your water allows you to control nutrient availability, prevent system failures, and improve crop yields.

By knowing exactly what your water contains, you can avoid wasting money on unnecessary fertilizers, reduce costs associated with restoring normal plant growth, and minimize expensive repairs to your fertigation and irrigation systems. In other words, smart water management not only protects your crops but also saves you significant resources over time.

Optimize Your Water Like a Pro

With the Growing Farm — calculate acid doses, buffer levels, and keep your irrigation and fertigation systems stable for healthier crops.

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