Farmers, Fertilizers, Water Pollution

Freshwater crustaceans used for toxicity testing.

November 20, 2012

Poultry litter and human biosolids have been commonly used as fertilizers for decades. However, at the Wye Research and Education Center, aquatic toxicologists Dr. Lance Yonkos and Dr. Daniel Fisher are studying the environmental fate and effects of contaminants found in these fertilizers.


While fertilizers help increase crop productivity, excess nutrients from their application are considered to be a major pollution problem. Additional contaminants found in poultry litter include natural reproductive steroids and pharmaceuticals, such as antibiotics administered for disease prevention and growth promotion. Biosolids are also used as fertilizers and are the product of human waste treatment in sewage plants. Since this process does not remove all contaminants, biosolids contribute to the increased levels of antibiotics found in soil. 

“The Delmarva Peninsula is one of the most densely concentrated poultry producing areas in the US,” explains Dr. Fisher. Most of the region’s litter is disposed of by applying it as organic fertilizer to fields. Antibiotics and steroids have been found in litter, soil, runoff, and receiving waters; suggesting a potential for a severe water quality problem in surface and ground waters throughout the Chesapeake Bay region.                                                                      


In laboratory fish studies, Drs. Fisher and Yonkos have found some worrying results. “Elevated steroid levels caused the appearance of a female egg-yolk protein in adult male fish and feminization of sex tissues in larval male fish,” explains Dr. Yonkos. The researchers have since taken their work into the field, and the study of wild fish populations uncovered for the first time, the presence of intersex largemouth bass in the lakes of the Delmarva Peninsula.

More recently, the researchers have been looking to control the runoff of contaminants from agricultural fields. “We have found that tillage practices have dramatic effects on the overland transport of contaminants following precipitation events,” notes Dr. Yonkos.  During initial rain events, and after litter application, fields managed using conventional and turbo-tillage produced lower steroid and antibiotic concentrations in runoff than those managed using no-till conservation tillage.

Drs. Fisher and Yonkos are currently investigating a promising “sub-surface litter injection procedure.” If proven successful, this procedure would dramatically reduce the runoff of overland nutrients, steroids, and antibiotics into receiving waters, thus leading to a significant pollution reduction in the Chesapeake Bay.