|Powell, J Mark|
Submitted to: Agricultural Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2004
Publication Date: 1/15/2005
Citation: Saam, H., J.M. Powell, D.B. Jackson-Smith, W.L. Bland, and J.L. Posner. 2005. Exploring the use of animal density standards for nutrient management policy on Wisconsin dairy farms. Agric. Syst., 84:343-357. Interpretive Summary: Farm size indicators, based on number of animals per farm, are currently used to direct manure management policy. However, it is becoming increasingly evident that all farms, regardless of size, may impact the environment. An alternative to herd size or location-based indicators for targeting manure management policy is animal density (the number of animals per unit of cropland). The objective of this study was to investigate the implications of using alternative definitions of animal density to target manure management policy for the Wisconsin dairy industry. Data from a representative sample (n=800) of all dairy farms in Wisconsin was used. Animal densities based on total cropland indicate that 95% of dairy farms have sufficient cropland for recycling the nitrogen (N) contained in manure. Animal densities based solely on tilled cropland decreased this value to 79%. Implementation of a phosphorus (P)-based standard reduced the overall amount of cropland available for manure application, and a smaller proportion of Wisconsin dairy farms (63% based on total cropland and 25% based on tilled cropland) would have sufficient land for recycling manure P. When the area of cropland on which manure is actually spread is used to calculate animal density, it is clear that the majority of dairy farms would not meet either manure N- or P-based manure application standards. Regional differences suggest soil texture, land ownership, and development pressures may limit the proportion of cropland receiving manure. The results of this study indicate the need to better understand factors influencing manure-spreading behavior on dairy farms. Unlike water quality-based indicators that are difficult to measure, animal density can be accurately assessed on each farm at low costs.
Technical Abstract: Animal density is increasingly being used as an indicator of manure nitrogen (N) and phosphorus (P) loss potential in Europe and the U.S. This study estimated animal densities (animal:cropland ratios) for approximately 800 Wisconsin dairy farms to (1) illustrate the impact of alternative definitions of this ratio, (2) evaluate how the definition of 'cropland' affects the proportion of Wisconsin dairy farmers affected by emerging government nutrient management standards, and (3) investigate the potential of using an animal density standard for targeting manure management plan implementation on Wisconsin dairy farms. Animal density calculations based on total cropland area indicated that 95 percent of Wisconsin dairy farmers have sufficient cropland for recycling manure according to a N-based nutrient management standard. Calculating animal density based on tilled cropland area decreased this value to 79% of dairy farms. Implementation of a P-based standard reduced the overall amount of cropland available for manure application, and fewer Wisconsin dairy farms (63% based on total cropland and 25% based on tilled cropland) would have sufficient land for recycling manure P. When the area of cropland on which manure is actually spread is used to calculate animal density, it is clear that the majority of farms do not currently meet either manure N- or P-based land application standards. Reasons for not utilizing the full cropland base for manure application are unclear, but regional differences suggest soil texture, land tenure, and development pressures may limit the proportion of cropland receiving manure. These results indicate the need to better understand factors influencing land-constraints and manure spreading behavior on Wisconsin dairy farms.