Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: October 1, 2004
Publication Date: January 1, 2006
Citation: Sistani, K.R., Novak, J.M. 2006. Trace metal accumulation, movement, and remmediation in soils receiving animal manure. Book Chapter. Trace Elements in the Environment (Biogeochemistry, Biotechnology, and Bioremdiation) 33:689-706 Interpretive Summary: Trace metals refer to those elements such as cupper, manganese, zinc that are required by many plants in small quantities. Cattle, poultry and swine feeds are frequently fortified with various levels of trace metals in order for maintaining various physiological processes and to avoid animal health disorders. Therefore, animal manure usually contains significant quantities of many trace elements. Agronomic crops normally assimilate much smaller quantities of trace metals compared to major nutrients. Consequently, if trace metal application rates exceed plant removal rates, then they will accumulate in soil. Research reports indicate that more than 20% of the cattle grazing in the field had liver Cu concentrations that exceeded the potential Cu toxic concentration of 150 mg/kg fresh weight. Soils with high trace metal concentrations can also be a point source of contamination for surface waters bodies and can cause occurrences of plant toxicity. Because trace metal accumulation in soils will probably have a long residence time, it is important to understand reasons for their accumulation and to determine soil factors controlling their mobility. An understanding of these factors is critical for the development of physical or chemical remediation strategies or adjustments in manure management practices to reduce trace metal accumulation. This book chapter reviews the research reports and information related to trace metals and animal manure management.
Technical Abstract: Trace metals are important components in an animal's daily food rations because they are essential for maintaining various physiological processes. Because some animal feeds contain inadequate supplies, trace metals are added in feeds to ensure an optimal supply and to minimize health disorders. Unfortunately, trace metal levels in feeds are frequently fortified to amounts greater than recommended to ensure adequate uptake. Trace metals not retained by the animal are excreted in manure. The return of manure to the land completes a natural recycling process. However, trace metals from manure-types are also known to be a potential source of pollution to the environment. The application of animal manures on agricultural lands as a fertilizer has the benefit of resource recycling and waste minimization from livestock production facilities. Research from around the world has shown, however, that continuous manure applications can cause their accumulation in soils because crop uptake of trace metals is small. Although trace metals are accumulating in manure treated soils, there are few reports of levels reaching phytotoxic threshold concentrations. High levels of trace metals in soils, however, can potentially pose a water quality risk when runoff or leaching transports trace metals into surface water sources. Research has shown that the risk of trace metals causing environmental problems is dependent upon the elements solubility and binding affinity to organic matter and minerals. Countermeasures to reduce trace metal concentrations in soils include phytoremediation and additions of soil chemical amendments. It is recommended that trace metal accumulation in soils may be avoided and/or reduced by optimizing their concentration in feed stocks, improving animal trace metal uptake efficiencies, and reducing application rates onto the same fields.