ONE OF THE OBJECTIVES of the Sustainable Land Application Conference was to provide an update on the body of literature related to the land application of biosolids and wastewaters since the previous major conference on this topic in 1993. An additional objective was to expand the scope to include other organic by-products such as animal manures. The purpose of this paper is to provide a broad overview of research and relevant issues for soil reactions of nutrients as constituents in land-applied agricultural and municipal by-products. Additional details on select topics are provided in subsequent papers in this section.
Earlier reports from conferences on plant nutrients in biosolids and wastewaters discussed nitrogen (N), phosphorus (P), potassium (K), sulfur (S), calcium (Ca), and magnesium (Mg) (Linden et al., 1983; Pierzynski, 1994). This report focuses on only N and P, as they have significant environmental implications that often determine residual application rates.
Previous interest in land application aspects of N and P focused on nutrient content, mineralization of organic N, variability in characteristics within and between treatment plants and processes, and nitrate movement. Ammonia volatilization and P chemistry and availability have only recently garnered attention. Plant nutrient issues remain a significant topic for land application due to existing and emerging environmental concerns.