The Manitoba Livestock Manure Management Initiative, Inc. (MLMMI) has identified five key areas for future research proposals to target when investigating the impact metals in livestock rations may have when excreted in manure and subsequently spread upon cropland.
Metals in livestock rations that are in excess of the animal’s nutritional requirements are not retained by the animal and will end up in the manure. When the manure is later applied to land, the excreted metals may become concentrated in the soil. Under certain conditions, excess concentrations of metals can have negative effects on crop yields and quality. There is also a concern that metals will eventually leach into ground and surface waters, causing contamination of those water sources.
Research suggests that most metals in manure are present at such low levels that it would take over a century of manure application for them to reach levels that pose an environmental problem. However, depending on the livestock management system, some metals may be present at higher levels and may accumulate in the soil more quickly.
The MLMMI is particularly concerned about selenium, copper, zinc and boron. Selenium, copper and zinc are intentionally added to animal feeds for nutritional and other purposes, but boron appears to be elevated in manure due to naturally elevated levels in some sources of livestock drinking water.
After reviewing the transfer of metals from animal feeds to the animal, then to manure, to soils and back into crops grown on the soils, five main research opportunities were identified. The MLMMI says future research proposals should address the following questions:
- What are the concentrations of metals found in the manures of swine, poultry, beef and dairy?
- What are the sources of these metals, including the levels found in typical animal rations?
- Are metals in livestock drinking water of concern?
- What effect does repeated land application of manure containing elevated metals have on soil and plant/crop quality?
- What will be the long-term effects of metals in manure on crop and soil quality, and will it be necessary to implement mitigation practices?
The Clean Environment Commission (CEC) believes that it is important to develop a better understanding of the background levels of metals in Manitoba soils, particularly in fields that are being fertilized with hog manure. Of the recommendations outlined in the CEC report titled “Environmental Sustainability and Hog Production in Manitoba” released March 3, 2008, was recommendation 9.14: stating “the Manitoba government facilitate, encourage, and undertake further studies in the assessment of heavy metals in Manitoba agricultural soils and potential environmental effects as a result of long-term application of manure.”
For more information, application forms and information about how to submit a proposal, visit the Manitoba Livestock Manure Management Initiative, Inc. Web site at www.manure.mb.ca/projects . Contact Street at (204) 945-2122 or email [email protected]  for assistance in setting up the project application.