Water quality for foliar feeding — the difference between pH and hardness

When preparing tank mixes, farmers traditionally pay the most attention to the choice of fertilizers, product compatibility, and spraying techniques. However, one of the most critical components – water, which makes up 90–95% of the working solution – is often overlooked. It is water quality that can significantly affect the efficiency of the entire treatment process, sometimes neutralizing the efforts and funds invested in expensive fertilizers and PPPs (plant protection products).

The effectiveness of foliar feeding is mostly influenced by two key water quality indicators: pH level and hardness. Although these parameters are often confused, they describe completely different properties of water and affect solution stability and nutrient uptake by plants in different ways.

What is Water pH?

Water pH is a measure of hydrogen ion concentration, which determines whether water is acidic, neutral, or alkaline. A neutral value is pH 7. Indicators below 7 indicate an acidic reaction, while those above 7 indicate an alkaline one.

For tank mixes, an optimal range is considered to be pH 4.0–6.5. At elevated pH levels (alkaline water), several negative processes occur: micronutrients convert into poorly soluble hydroxides and phosphates, certain fungicides and growth regulators degrade rapidly, and the overall treatment efficiency can drop by 30–50%. Even if fertilizer rates are calculated correctly, plants simply will not be able to fully absorb them.

What is Water Hardness?

Water hardness is determined by the concentration of dissolved calcium (Ca) and magnesium (Mg) salts. Unlike pH, hardness has no direct relation to acidity or alkalinity. Water can have an ideal pH of 5.5–6.0 but still be highly hard.

The main issue with hard water lies in the chemical interaction of Ca²⁺ і Mg²⁺ ions with the components of the tank mix. As a result, insoluble compounds (calcium phosphates, carbonates, sulfates) are formed and precipitate. This is particularly critical for phosphorus and sulfate forms of fertilizers, as well as many PPPs. Consequently, a portion of the nutrients is lost right inside the sprayer tank, clogging filters and nozzles, and a significantly lower amount of active ingredients reaches the leaves.

Why is it Important to Control Both Indicators Simultaneously?

There is no direct correlation between pH and hardness. Water can be soft but highly alkaline, or hard at a neutral pH. Acidifying water lowers the pH but does not solve the problem of excess calcium and magnesium. Therefore, to ensure the stable performance of tank mixes, you need to manage both parameters.

Consequences of Using Poor Quality Water:

• Reduced solubility and availability of fertilizers;

• Sediment formation in the tank;

• Poorer nutrient uptake through the leaves;

• Clogging of sprayer filters and nozzles;

• Uneven application of the working solution;

• Waste of money on expensive products;

• Decline in overall treatment efficiency.

In many cases, farmers blame poor results on the weather, fertilizer quality, or incorrect technology, whereas the real cause is the water.

How to Test and Improve Water Quality?

The easiest way is regular pH measurement using a portable pH meter or high-quality test strips. Hardness can be determined with test kits (in dH degrees or mg/L CaCO₃). However, for a complete picture, it is best to perform a laboratory water analysis – this will provide data not only on pH and hardness but also on the content of sulfates, chlorides, organic matter, and other components.

Practical Solutions:

1. At high pH levels, use specialized pH correctors that not only acidify but also stabilize the pH level in the tank.

2. In case of high hardness, apply water conditioners that bind calcium and magnesium ions into inactive complexes.

3. Always follow the correct mixing sequence of components (first water conditioner/pH correctors, then fertilizers, PPPs, adjuvants).

4. Be sure to perform a jar test in a small volume (1–2 liters) before filling the sprayer.

Thus, water quality is the foundation of effective foliar feeding. Controlling pH and hardness allows maximizing the potential of fertilizers, saving money, and achieving a consistently high result. Water analysis should become a mandatory preparation step for every treatment, especially in regions with hard water.