Skip to main content
ARS Home » Southeast Area » Booneville, Arkansas » Dale Bumpers Small Farms Research Center » Research » Research Project #434319

Research Project: Determining the Potential Causes of Soil Acidification in the Mulberry River Watershed, Arkansas

Location: Dale Bumpers Small Farms Research Center

Project Number: 6020-21310-011-025-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Apr 1, 2018
End Date: Mar 31, 2023

The objective of this research is to determine the relative effects of forest species, atmospheric ammonia deposition and acid rain on soil acidification in the Mulberry River Watershed in Arkansas.

The Mulberry River was listed in 2008 on the Arkansas 303(d) list of impaired waterbodies due to low pH. The objective of this research is to determine the amount of acidity generated by three potential sources; (1) converted hardwood forests to pine, (2) atmospheric deposition of ammonia, and (3) acid rain. Large areas of the watershed are being converted from hardwood to pine forest and the chemical properties of leaf litter of these trees differ considerably, hence, an increase in pine forests could explain the increased soil and water acidity. Another potential cause of soil acidification is the atmospheric deposition of ammonium from animal agriculture, since roughly 700 million broiler chickens are grown in northwest Arkansas. Ammonium deposition does not directly lower the pH of soil and water. However, when ammonium is nitrified in the soil or water by bacteria in the process of nitrification, it results in the production of hydrogen ions, thereby lowering the pH. While acid rain has been greatly reduced since the passage of the Clean Air Act, it still exists and may also be a cause of acidification. We will determine the effects of forest species on soil acidification. Soil acidification measurements will be made on soils in existing hardwood forests and adjacent paired pine forests of various age, stand densities, etc., located within the same or similar soil types.