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From product efficacy to ease of application, it is important to get your pH levels right.

With heightened awareness around agronomic practices, growers are becoming increasingly aware of the benefits of knowing and managing pH levels in the soil. However, it is important not to forget that pH levels of the water you use can have a significant impact in the sprayer.

Let’s look at four reasons why pH levels matter in spray solutions, along with recommendations to help you avoid any concerns.

1. pH affects the stability and performance of insecticides.

Pesticide performance (especially insecticides) can be dramatically affected if the water you use is alkaline (with a pH between 7.5 and 9.0). This can lead to alkaline hydrolysis, which causes the pesticide to decompose to an inactive form – resulting in poor insect control.

The solution: Decomposition can be slowed or prevented by using an acidifying product solution to achieve a pH level of 6.0 or below. Acidified pesticide sprays frequently provide improved initial pest control and longer residual control.

CLICK HERE for list outlining recommended pH levels for a number of common insecticides, fungicides and herbicides (by product name and active ingredient).

2. Your pH impacts solubility and nutrient uptake.

Nutrients must be present in water-soluble form for effective plant uptake. Fertilizer and nutrient products that have a neutral pH and low water solubility make it hard for plants to immediately absorb the nutrients.

The solution: Acidifying the water to a safe level will increase solubility of nutrients within the spray tank, making them more readily available for plant uptake. Where quick response is desired, such as in fast-growing crops or where deficiency correction is urgent, this effect is especially important.

3. Foliar sprays require an acidic pH for proper absorption.

Foliar absorption is pH dependent. The pH level regulates the complex electrostatic repulsion and attraction phenomena within the plant’s cuticle. For example, it is believed that the optimal pH level for phosphate absorption and utilization is between 3 – 3.7. There is evidence that zinc is absorbed best at a pH range between pH 4.1 – 4.9. While much research needs to be done, it is clear that optimal pH levels vary according to each nutrient and its carrier.

The solution: Again, acidify the water and seek the advice of an agronomy professional if required.

 4. Extreme pH imbalances can burn the plant surface.

Plants are generally tolerant of sprays with a wide range of pH. Naturally, extremes at either end of the pH scale should be avoided.

Phytotoxicity is a chief concern. A spray solution with a significant pH imbalance can “burn” the plant, and result in soft tissue death, stunting, russeting, leaf spotting, dead leaf tips, dead areas between leaves and distortion of the leaves and reproductive organs

The solution: Avoid extreme pH levels in a spray solution. Spray solutions should not be acidified if they contain lime, lime sulfur, or fixed copper products where copper may become solubilized by the acidity resulting in possible plant injury.

Note: Other factors besides pH that affect phytotoxicity are concentration, salt index, chemical reactivity, and weather conditions.

 Tips for managing pH levels in your spray solutions.

As you can see, pH plays an important role in the performance of your spray solutions. To summarize:
 

• As a general practice, spray solutions work best in an acidic solution (pH 4.0 – 6.0).

 

• Pesticides are most effective at a pH of 6.0 or below.

 

• Phosphate is absorbed best at a pH slightly below 4.0.

 

• Most spray products become more soluble as pH decreases.

 

• Extremely high or low pH levels can cause leaf burn.

 

• Spray solutions should not be acidified if they contain lime, lime sulfur, or fixed copper products, carbonate, hydride.

 

• Acid spray solutions help control certain fungi and may be a factor in maintaining populations of some beneficial insects.

 

It starts by knowing the pH level of your water supply. When it comes to product mixing and compatibility, always follow the labels and consult with your farm supply retailer if you have any questions. They may recommend use of an acidifying product or a tank mix adjuvant designed to improve solubility, compatibility and efficacy.

Additional reading: Fact Sheet- The Importance of pH Control in Spray Solutions