Global Review of Winter Manure Application Regulations and Guidelines.

Application of animal manure to frozen and snow-covered soils can increase the risk of nutrient losses and impairment of water quality in regions with hardy winters. In conjunction with global distributions of animal densities, we reviewed world-wide regulatory and voluntary guidelines on winter manure management to reduce off-site nutrient losses. Almost all developed countries have guidelines to restrict winter manure applications either completely (e.g., European Union member nations), or partially (e.g., most states/provinces of United States, Canada, and New Zealand). Approaches range from restricted manure application over large periods of time to guidelines based upon field conditions. In USA, guidelines for Concentrated Animal Feeding Operations (CAFOs) are often stricter than for non-CAFOs. In contrast, there is a paucity of such guidelines in developing countries such as China, despite an increasing animal production industry and concern over water quality. This review explores the causes of variability in guidelines and highlights opportunities to advance existing guidelines.