The goal of this project was to identify agricultural soils reflected in the acetochlor label use restriction, which overlap with shallow ground water. Acetochlor-based products are labeled for use within the United States to control annual grasses and certain broadleaf weeds and can be applied preplant, at-planting, preemergence and/or postemergence to labeled crops. Acetochlor product labels restrict applications within 50 feet of any well where depth to ground water is ≤ 30 ft. The Acetochlor Registration Partnership (ARP - Dow AgroSciences and Monsanto Company) developed voluntary Best Management Practices (BMPs) for acetochlor to reduce the potential for the active substance and its major environmental metabolites in ground water and surface water, following application to agricultural fields. The ARP offers a website (www.arpinfo.com) with resources for end-users to help ensure the effective use and stewardship of products containing acetochlor. Depth to ground water information is often not readily available, which makes it challenging to depict the spatial distribution of areas where the use restriction should be observed. One can point to privacy concerns as a reason for the lack of ground water depth information available to the public. An assessment was conducted to identify crop lands with potential acetochlor use restrictions in Arizona, using geospatial techniques. Arizona’s Department of Water Resources provides historical ground water depth data for point locations via a public monitoring database (http://www.azwater.gov/azdwr/GIS/). Groundwater depth information was extracted from the monitoring database for the period 1995 to 2015. As a data handling procedure, outliers were removed, then cluster and hotspot analyses were performed. The final dataset contained over 12,000-point observations of ground water depth for a 20-year period. Long-term average depths were calculated for each location. To generate a state-wide average groundwater depth map, a spatial interpolation technique was applied to the GIS vector or point dataset. The final ground water map was overlaid with National Agricultural Statistics Service (NASS) Cropland Data Layer (CDL) data to identify agricultural soils with potential concerns. For cotton, the assessment showed that just 3% of the agricultural areas overlap with shallow ground water.

Using geospatial techniques for effective product stewardship

256th National Meeting (2018)

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