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Weed seed viability in composted beef cattle feedlot manure
Francis J Larney1, Robert E Blackshaw
1Agriculture and Agri-Food Canada, Research Centre, 5403 1st Avenue S., Lethbridge, Alberta, Canada T1J 4B1. larney@agr.gc.ca
Journal of Environmental Quality
|June 18, 2003
Summary
Composting beef cattle manure effectively reduces weed seed viability, though some species may survive longer composting periods. Temperature alone does not fully explain weed seed destruction during manure composting.
Area of Science:
- Agricultural Science
- Environmental Science
- Botany
Background:
- Manure composting is increasingly adopted by the beef cattle feedlot industry.
- Compost is often marketed as a weed-free product, but its efficacy against weed seeds requires validation.
Purpose of the Study:
- To investigate the impact of feedlot manure composting on the viability of weed seeds.
- To determine the relationship between composting conditions (temperature, time) and weed seed destruction.
Main Methods:
- Weed seeds of various species were buried in open-air compost windrows.
- Seed viability and respiration were assessed at different time points during the thermophilic composting phase.
- Windrow temperature and moisture content were monitored throughout the study.
Main Results:
- Composting significantly reduced weed seed viability, with zero germinability observed for most species within the study period.
- Some seeds retained viability and respiration capacity even after extended composting (e.g., Day 70).
- Lethal temperatures for weed seed elimination varied by species, with some requiring >60°C, while others were affected by 39°C within 7 days.
Conclusions:
- Manure composting is a viable method for reducing weed seed viability in beef cattle feedlots.
- Temperature is a critical factor, but not the sole determinant; other factors influence weed seed survival during composting.
- Species-specific responses highlight the complexity of weed seed inactivation in compost.