Craven County Survey of Water Quality Impacts on Pesticides

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Two critical water qualities that may impact pesticide application are the water pH and the amount of carbonates, or hardness. Within Eastern North Carolina, these qualities may vary greatly as noted by the image below. As such, whether one uses a private well, stream or surface water or a municipal water source, these parameters will vary greatly and should be evaluated before making pesticide applications.

Stream and Groundwater pH varibility

Stream and Groundwater pH

Ideally, one should apply pesticides in a water solution that has a pH range of 5.5-6.5. Regrettably, within Craven County, NC, the water pH values are near neutral to slightly basic. Having thus said, a few shallow wells may very acidic. Neither water pH is desired since improper pH may rapidly decrease the pesticide half-life.

Impact of water pH on half-life of pesticides. Acid water improves half life

Impact of water pH on half-life of pesticides

In addition to water pH, high carbonates in water will lead to slower absorption rate of pesticides, result in degradation of active ingredients, or may cause excessive salt accumulation within hoses and nozzles that result in poor distribution of the pesticide. Water with high carbonates will also negatively impact salt-formulated pesticides (glyphosate, glufosinate, and 2, 4-D as examples) much greater than others. Carbonate levels much above 300 ppm are considered hard water and are too high. Within Craven County, both private wells and municipal water sources tend to be very high in carbonates.

To assist in management of these potential water quality issues that may negatively impact pesticide application, N.C. Cooperative Extension in Craven County is conducting a survey of water samples for commercial applicators and farmers. We aim to test water sources through the 2022 production season. We hope to use this information to create a database to determine what, if any, corrective measure should be taken. To participate, simply email your name, address, number of water sources, and whether these are county water or well water sources to or call us at 252-633-1477 for more information.

Please note that we need to run the water source for at least 10 minutes prior to taking a sample. As such, it will be helpful to you if we take the sample when you are already planning to fill up a tank or greenhouse. Just work to schedule this when it is feasible for you to provide a bit of time to assist.

One does not need to participate in this survey to determine water quality. The N.C. Department of Agriculture and Consumer Services Agronomic Division offers water sampling for a fee. The report provides significant details of the water including recommendations for correction. To have this test performed, simply fill out Form AD-7 and follow the directions on the form for handling and submission.

Corrective actions for poor water will vary. Typically, adding battery acid or buffering solutions are recommended for high water pH and high carbonates (The NCDA&CS Agronomic Division reports hard water levels as “Alkalinity). Too, additions of ammonium sulfate (AMS) at about 8-17 lbs. per 100 gallons of water is often used. However, liquid nitrogen (24%, 28%, 32% N or products such as 10-34-0) at 1.25 – 2.5 % per 100 gallons may also be used. Lastly, mixing the pesticide immediately prior to application is feasible.

Regrettably, there is no list of pesticides that may be impacted by water quality. Even noting active ingredient of pesticides is not sufficient since the pesticide formulation, additives, or the presence of multiple active ingredients will alter decisions. The label of each product must be read to determine what, if any, actions should be taken.

An excellent resource is “The Impact of Water Quality on Pesticide Performance” provided by Purdue Extension. Or for more specific discussion of potential corrective measures based on water sample results, contact your local N.C. Cooperative Extension office.

Written By

Mike Carroll, N.C. Cooperative ExtensionMike CarrollCounty Extension Director, Field Crops & CRD Call Mike Email Mike N.C. Cooperative Extension, Craven County Center
Updated on Mar 25, 2024
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