HOW WE DEVELOP AND SUPPORT P-BASED REGULATIONS FOR LAND-APPLIED RESIDUALS

Authors: Sharpley, Andrew; SIMS, TOM - UNIV OF DELAWARE

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 2/20/2006
Publication Date: 3/15/2006
Citation: Sharpley, A.N., Sims, T. 2006. How we develop and support p-based regulations for land-applied residuals [abstract]. ASA-CSSA-SSSA Annual Meeting Abstracts.Paper No. 36-4.

Interpretive Summary: An interpretive summary is not required.

Technical Abstract: Over the last 20 years, there has been an increased occurrence of harmful algal blooms, such as Pfiesteria and cyanobacteria, in fresh waters of the U.S.A. These blooms have been linked to greater inputs of phosphorus (P). Having impaired human health and drinking-water treatment, they have culminated in recent voluntary and regulatory guidelines for managing P-rich residuals (i.e., animal manures and biosolids) applied to agricultural land. Although there is a wealth of agronomic trials determining P applications that meet crop yield goals, environmental P-risk assessment of land-applied residuals has until recently been based on expert advice, unfounded assumptions, and in some cases uneducated guesses. Methods have been developed to determine the environmental activity or mobility of P in residuals, which range from measures of water extractable P and other factors influencing P mobility in soil (e.g., Al, Fe, Ca, pH), to site assessment of P loss risk (which will be presented). In spite of supporting field-based research (which will be shown), there is a reluctance of regulators to consider adopting guidelines that address all factors that researchers know control P loss. This is often due to overly complex guidelines, a desire for guidelines to be based on state-specific data rather than regional or national data, but most notably, because clearly-defined, black and white regulations, which are needed to be enforceable, cannot adequately represent the environmental uncertainties associated with the risk of P loss (i.e., climate, edaphic, and socio-economic variability). Although several states have met this challenge, there is still the hurdle of making regulations flexible enough to allow modifications of guidelines in a timely manner to reflect new research and a better understanding of factors dominating the potential for P loss from land-applied residuals.