AG RETAILER GROUP CONTINUEs commitment toward clean water

Ankeny, Iowa — Agriculture’s Clean Water Alliance (ACWA) members have reaffirmed their agreement to protect Iowa’s water resources. 

The group of 11 ag retailers recently agreed to the voluntary Code of Practice for Nitrogen Fertilization, which the group has committed to annually for the last 21 years. The Code of Practice stipulates that fall applications of anhydrous fertilizer without a nitrification inhibitor be delayed until soil temperatures are 50 degrees Fahrenheit and trending lower.

“Since 1999, this group of ag retailers has come together in support for cleaner water,” said Brent Low, ACWA president and Ag Partners agronomy vice president.  “The board reviews and affirms the elements within the Code of Practice annually, which covers 20 counties of our members’ trade area.”

Although ACWA members are in direct competition, they have been united in the goal of improving and protecting water quality in the Des Moines and Raccoon River watersheds long before the Iowa Nutrient Reduction Strategy was established. Committing to this Code of Practice is a condition of being an ACWA member and it has become an annual custom.

Every autumn is different and soil temperatures can vary across the watershed geography. Usually soil temperatures turn cooler first in north and west-central Iowa compared to south and central Iowa. Historically, soil temperatures in this 20-county region are at or below 50 degrees and trending cooler in late October. Reporting from ACWA members validates conformance with the Code of Practice agreement. For example, member-reported application starting dates from the last five years were: Oct. 21, 2019; Oct. 22, 2018; Oct. 25, 2017; Oct. 22, 2016 and Oct. 23, 2015.

 Soil temperature is one of the important conditions to consider for nitrogen management. Colder soils hinder the conversion of ammonium nitrogen (NH4+) to nitrate (NO3). According to an article by John Sawyer, agronomy professor at Iowa State University (ISU), “ammonium is not leached or lost by denitrification (conversion to nitrogen gas). Therefore, it will stay in soil even if the soil becomes excessively wet. …Nitrate is leachable and subject to denitrification.”

ACWA members use a website managed by ISU as a decision tool for beginning fall fertilizer applications. The website shows the three-day, 4-inch depth soil temperature estimates for every Iowa county:

While soil temperature is one aspect of the Code of Practice, ACWA members also support farmer adoption of strategies to minimize loss of nitrogen to water sources. These can include the use of nitrogen stabilizers as well as conservation practices such as cover crops and no-till and incorporating edge-of-field practices including stream oxbow restorations, bioreactors, saturated buffers, and constructed wetlands. These practices can work together to treat nutrients lost from farm fields and improve water quality.

The historical focus of ACWA began with a concern for downstream water quality within the Des Moines and Raccoon River watersheds.  In 2000, the organization began stream water monitoring in these two watersheds to address downstream nitrate levels in the rivers that supply drinking water to Des Moines.

“ACWA members know water quality is just as important as proper nutrient management,” said Roger Wolf, ACWA executive director. “Continuing with water monitoring can help assess progress and target areas to have a greater impact toward water quality improvement. Stream water monitoring and the Code of Practice agreement go hand-in-hand to address and improve water quality in Iowa and further downstream.”

For more information, visit the ACWA website:



Agriculture’s Clean Water Alliance (ACWA) is an association consisting of 11 ag retailers and five associate members that support farmer customers in the Des Moines and Raccoon River basins. The ACWA mission is to help agriculture identify and implement solutions that reduce nutrient loss to Iowa waters.