How to Adjust Water PH for Agriculture Use

Irrigation Boom

PH is the measure of the hydrogen ion concentration in a solution. PH takes on values from 0 to 14, with 0 representing the most acidic solution and 14 the most alkaline. The pH of agricultural water plays a critical role in plant health, and it influences the efficacy of pesticides and growth regulators. Plants grow best in a slightly acidic (pH 6.0 to 6.5) soil solution, and the pH of the water used to mixed growth regulators and pesticides controls the chemicals' half-life.

Things You'll Need

• PH meter or soil test kit
• 5-liter bucket
• Water sample
• Gloves
• Buffer (optional)
• PH up
• PH down
• Graduated cylinder
• Paper
• Pen
• Calculator

Instructions

1. Fill your bucket with a sample of the water in question. Write down the volume of water you are testing.

2. Measure the water pH with your pH meter or pH strips.

3. Determine what you need to do to adjust your pH. For irrigation water, you want the pH to be around 6.0 to 6.5. If you are testing water to be used as a solution for a pesticide, read the instructions on the pesticide bag. If your water sample is close to the range you want, you may add a buffer. If your pH is really low, you will want to add pH up; if it is too high, add pH down.

4. While wearing gloves, add a small amount of your chosen adjuvant to your water. For precision, measure the adjuvant with your graduated cylinder. General instructions should be listed on your adjuvant's package. Add a little bit of adjuvant at a time, mixing thoroughly each time. After each mixing, measure the pH; if necessary, add more adjuvant.

5. Determine the ratio of volume of adjuvant added to volume of water in sample that gave you the desired pH. Once you have this ratio, multiply it by the total amount of water you need to remediate to give you the amount of adjuvant you need to add to the water.

Tips & Warnings

• An electronic meter is the most accurate way to measure pH. However, if you don't want to purchase an electronic meter, you can use the pH test strips that come in a pH test kit.

• The use of a buffer is optional and is only recommended in the situation where the pH of your water is very close to the optimum pH. Buffers resist changes in pH, so when you add a buffer it will be harder to adjust the pH of the water.

• Gardening supply stores usually sell pH-adjusting chemicals by the generic names pH up and pH down. Don't expect the adjuvant to go by its chemical name.

• There are many variations of acids, bases and buffers. That is why it is imperative to follow the instructions given on the packages of the chemicals you purchase.

References

• The University of Tennesee Agriculture Extension Service: Irrigation Water Quality for Greenhouse Production
• Colorado State University: Agriculture Water Quality Criteria

Resources

• Texas Greenhouse Management Handbook:Treating Irrigation Water