Water Hardness Wreaking Havoc with Pesticide Applications?

Jesse Fulbright, MSU Liberty County Extension

At a time of the season when there are plenty of times when spraying is an ongoing practice, let’s take a couple of minutes to talk about something that might make your pesticide applications less effective: water hardness.

According to an MSU Extension MontGuide titled, “Pesticide Performance and Water Quality,” the term water ‘hardness’ refers to presence of metals with a positive charge of more than 1, such as calcium, magnesium, and iron.  Total hardness is measured in parts per million (ppm) or in grains per gallon and labs typically report results in terms of calcium for simplicity, even though other metals are making up part of the hardness.  One grain (per gallon) equals 17.1 ppm.

These cations, or positively charged elements, can further reduce the effectiveness of weak acid pesticides, especially if the pH of the water is above the ideal range, which is so often true in our area.  The effect happens because of the pesticide dissociating into positively and negatively charged parts and the elements, such as calcium, magnesium and iron in the water, binding with the negatively charged portion of the pesticide.  This results in molecules that either can’t be absorbed by the target pest, enter at a slower rate, or form insoluble salts.  Hardness can range anywhere from 0 to over 800 ppm.  Water with a hardness between 0 and 114 ppm is considered soft, 114-342 ppm, moderately hard, 342-800, hard, and anything above 800 ppm is considered extremely hard.

Consider the following guidelines regarding hard water:

•Always read and follow precautions regarding hardness on the pesticide product label.

•Weak acid pesticides such as clopyralid, 2,4-D amine, glyphosate and dicamba may lose efficacy if hardness exceeds 150 ppm, especially if pH is greater than 7.0.

•2,4-D amine formulations can be totally deactivated if the hardness is greater than 600 ppm.

•Many other herbicides will lose efficacy if hardness is greater than 400 ppm, if iron is present.

Hardness can be reduced with the addition of dry ammonium sulfate at 8.5 to 17.5 lbs. per 100 gallons of water, or liquid fertilizers (such as 28 percent N, 32 percent N, or 10-34-0) at a rate of 1.25 – 2.5 percent per 100 gallons.  It works by reducing the pH and also through sulfate combining with hard water cations.  Performance might be enhanced further by the addition of a non-ionic surfactant.

If you have questions regarding your water hardness, please consider visiting with your local county Extension office about water testing options.

Pesticide Applications- Water Quality

Jesse Fulbright, MSU Liberty County Extension

It is not uncommon, according to an MSU Extension MontGuide, for Montana applicators to use water sources with pH levels higher than 8.0 and/or hardness ratings greater than 150 ppm.  This poor water quality can affect pesticide product performance, and as a result, product application rates often being raised, resulting in unnecessary losses in revenue.

In trying to work with water pH, remember that most insecticides, fungicides and herbicides are weakly acidic; that is when they are placed in water with a higher pH, over 7, they undergo degradation.  You can test your water with a litmus strip, or a pH meter.  Keep in mind that the pH of your water can vary with time and should be reassessed periodically.  Commercial buffers are available that can lower the pH of a spray solution for those weakly acidic pesticides.

Hardness, or hard water, refers to the presence of metals with a positive charge of more than 1, such as calcium, magnesium and iron.  The effect of water hardness is the further reduction of the effectiveness of weak acid pesticides, especially with a high pH water.  Hardness can be reduced with the addition of dry ammonium sulfate at 8.5 to 17.5 lbs./100 gallons of water, or liquid fertilizers, such as a 10-34-0 at a rate of 1.25 to 2.5% per 100 gallons.  Performance might be further enhanced by the addition of a non-ionic surfactant.

Turbidity can also affect pesticide performance.  This is simply the haziness of a liquid caused by suspended particles, such as soil and organic matter.  Applicators can test water turbidity by dropping a quarter into a five-gallon bucket filled with water.  If the water is too cloudy to see the quarter, seek an alternative source of water for spray mixtures.

If you have questions about your water quality, I would encourage you to contact your local county Extension office for more information, or for a copy of the MontGuide, titled, “Pesticide Performance and Water Quality.”

Spring Runoff and Water Testing

Kari Lewis

As MSU Extension educators, we commonly recommend soil tests, forage tests, and water tests.  Well water testing should be done annually and is especially recommended in years like this where there has been increased runoff.  If your well has been flooded or if you notice a change in water quality, it’s especially important to have a test done. 

There are a vast number of people and resources devoted to monitoring municipal water supplies.  For the private well water user, however, it is up to them to monitor the well water quality and ensure water quality meets drinking quality standards. 

The MSU Extension Well Educated program provides well owner education as it relates to health and quality of life.  Through the Well Educated program, free water collection bottles are available at your local Extension office that can then be sent to a Montana lab for analysis.  A few of the frequent questions related to this program include what parameters should be tested for, and how much does the testing cost?

What the water will be used for determines what the water should be tested for.  If the water will be used for drinking water and hasn’t been tested in recent years, then a basic domestic analysis that measures alkalinity, bacteria, nitrate, pH, and total dissolved solids, is an appropriate choice and is only $35.   A basic annual analysis is the minimum test that all private well owners should complete each year.  The basic analysis, available for $20, measures bacteria and nitrates, and is a valuable tool to track water quality through time. 

Farmers and ranchers should also consider testing their livestock drinking water and irrigation water.  The ‘Suitability of Water for Livestock’ test is $50, and can help identify any parameters which could deter livestock from drinking water and potentially cause health issues or lower livestock performance. 

Another reason to test livestock water is to measure nitrate presence.  If livestock are consuming feeds that contain nitrates (such as grain hay), and are also drinking nitrate containing water, the cumulative effect can reduce livestock performance and cause abortions.  Nitrate levels are often higher after spring runoff. 

Water quality can frequently change from year to year depending on amount of runoff, severity of drought, and other environmental conditions.  Rural residents drinking well water, farmers, and ranchers should stop by the MSU Extension office to pick up a free water testing kit to collect a water sample from a home well, livestock water, and/or irrigation water.  Water samples should be collected and shipped the same day, Monday through Wednesday, and results are typically available within two weeks. 

For additional information regarding water testing or for your free water collection bottles, please contact your local MSU Extension Office.